THE INFLUENCE OF RAINFALL VARIABILITY ON IRRIGATED CITRUS PRODUCTION IN THE GREATER TZANEEN MUNICIPALITY, LIMPOPO PROVINCE, SOUTH AFRICA
THE INFLUENCE OF RAINFALL VARIABILITY ON IRRIGATED CITRUS PRODUCTION IN THE GREATER TZANEEN MUNICIPALITY, LIMPOPO PROVINCE, SOUTH AFRICA
Student Number: 14014023
A research dissertation submitted to the Department of Geography and Geo-Information Sciences, School of Environmental Sciences in partial fulfilment of the requirements for the award of the Bachelor of Environmental Sciences Honours Degree in Geography at University of Venda
SUPERVISOR: MR. E KORI
UNIVERSITY OF VENDA
SCHOOL OF ENVIRONMENTAL SCIENCES
DEPARTMENT OF GEOGRAPHY AND GEO-INFORMATION SCIENCES
DECLARATIONI, TANGANEDZANI TSHITAVHE, hereby declare that the dissertation for the Bachelor of Environmental Sciences Honours Degree in Geography at the University of Venda, hereby submitted by me, has not been submitted previously for a degree at this or any other university, that this is my own work in design and execution, and that all reference material contained therein has been duly acknowledged.
DEDICATIONTo Mr N.A Dzaga and Mrs N.E Dzaga.
ACKNOWLEDGEMENTS”Trust in the Lord with all your heart, and lean not on your own understanding, in all your ways acknowledge him and he shall direct your paths.” Proverbs 3:5-6. I would like to thank the Lord, God almighty for he made it all possible for me.
I would like to express my sincere gratitude and deep appreciation to:
My supervisor, Mr. E Kori for his boundless, insightful and professional advice that he provided me from the formative stages of this thesis, to the final draft. Had it not been for his commitment careful through and conscience reading of the manuscript, unlimited guidance, patience and follow up as well as provision of critical comments and suggestions this thesis would not have been achieved. His constructive criticism is much appreciated.
National Research Foundation (NRF) Research and Innovation for funding this research project.
Irrigated citrus farm owners in the Greater Tzaneen Municipality for their assistance and allowing me to conduct the research in their farms.
South African Weather Services for the provision of rainfall data. Without their data the thesis could not have been a success.
My parents, Mr. N.A Dzaga and Mrs. N.E Dzaga I am extremely grateful for their love, support, understanding, encouragement, sacrifices for my education and preparing me for my future. I extend my deepest appreciation.
My uncle, Mr. M.E Ndadza for his support, tolerance and shelter. Thank you.
To all these people I would like to say: May God give you all the desires of your hearts, more strength and courage in everything you do.
TABLE OF CONTENTS
TOC o “1-3” h z u DECLARATION PAGEREF _Toc504735338 h iiiDEDICATION PAGEREF _Toc504735339 h ivACKNOWLEDGEMENTS PAGEREF _Toc504735340 h vLIST OF TABLES PAGEREF _Toc504735341 h ixLIST OF FIGURES PAGEREF _Toc504735342 h xLIST OF APPENDICES PAGEREF _Toc504735343 h xiLIST OF ABBREVIATIONS AND ACRONYMS PAGEREF _Toc504735344 h xiiABSTRACT PAGEREF _Toc504735345 h xiiiCHAPTER 1: BACKGROUND TO THE STUDY PAGEREF _Toc504735346 h 11.1 Introduction PAGEREF _Toc504735347 h 11.2 Problem Statement PAGEREF _Toc504735348 h 21.3 Research Questions PAGEREF _Toc504735349 h 31.4 Research Aim and Objectives PAGEREF _Toc504735350 h 31.4.1 Research Aim PAGEREF _Toc504735351 h 31.4.2 Research Objectives PAGEREF _Toc504735352 h 31.5 Delimitation of the Study and Study Area PAGEREF _Toc504735353 h 31.5.1 Focus of the Study PAGEREF _Toc504735354 h 31.6.2 Description of the Study Area PAGEREF _Toc504735355 h 41.7 Justification for the Study PAGEREF _Toc504735356 h 51.8 Definitions of the Key Terms PAGEREF _Toc504735357 h 61.9 Chapter Summary PAGEREF _Toc504735358 h 6CHAPTER 2: LITERATURE REVIEW PAGEREF _Toc504735359 h 72.1 Climate and Weather Variability PAGEREF _Toc504735360 h 72.2 Rainfall Trends and Change PAGEREF _Toc504735361 h 82.3 Rainfall Seasonality PAGEREF _Toc504735362 h 92.4 Rainfall Variability in Limpopo Province PAGEREF _Toc504735363 h 102.5 Irrigation and Rainfall PAGEREF _Toc504735364 h 122.6 Rainfall Variability and Citrus Yields PAGEREF _Toc504735365 h 132.7 Rainfall Variability and Crop Production PAGEREF _Toc504735366 h 142.9 Rainfall Variability Adaptation Strategies PAGEREF _Toc504735367 h 172.10 Chapter Summary PAGEREF _Toc504735368 h 18CHAPTER 3: RESEARCH METHODOLOGY PAGEREF _Toc504735369 h 193. 2 Data Collection Methods PAGEREF _Toc504735370 h 203.3 Ethical Consideration PAGEREF _Toc504735371 h 213.4.1 Seasonal Rainfall Variability PAGEREF _Toc504735372 h 213.4.2 Rainfall Variability and Irrigation Patterns PAGEREF _Toc504735373 h 223.4.3 Rainfall Variability and Citrus Production PAGEREF _Toc504735374 h 233.5 Data Presentation PAGEREF _Toc504735375 h 243.6 Chapter Summary PAGEREF _Toc504735376 h 24CHAPTER 4: RESULTS AND DISCUSSION PAGEREF _Toc504735377 h 254.1 Seasonal Rainfall Characteristics of the Greater Tzaneen Municipality PAGEREF _Toc504735378 h 254.2 Seasonal Rainfall Variability and Seasonal Citrus Irrigation Patterns PAGEREF _Toc504735379 h 294.3 Citrus Irrigation Patterns and Citrus Production Relationship PAGEREF _Toc504735380 h 354.4 Rainfall Variability and Citrus Production Relationship PAGEREF _Toc504735381 h 374.5 Chapter Summary PAGEREF _Toc504735382 h 39CHAPTER 5: SUMMARY, CONCLUSION AND RECOMMENDATIONS PAGEREF _Toc504735383 h 405.1 Summary of Findings PAGEREF _Toc504735384 h 405. 2 Conclusion PAGEREF _Toc504735385 h 415.3 Recommendations PAGEREF _Toc504735386 h 415.4 Recommendation for Further Research PAGEREF _Toc504735387 h 42REFERENCES PAGEREF _Toc504735388 h 43APPENDICES PAGEREF _Toc504735389 h 53
LIST OF TABLES TOC h z c “Table” Table 1: The Research Matrix PAGEREF _Toc505457814 h 20Table 2: Precipitation Concentration Index PAGEREF _Toc505457815 h 22Table 3: Seasonal rainfall distribution (Weather Station 1: Westafalia) PAGEREF _Toc505457816 h 26Table 4: Seasonal rainfall distribution (Weather Station 2: Vergelegen) PAGEREF _Toc505457817 h 27Table 5: Seasonal rainfall distribution (Weather Station 3: New Agatha-BOS) PAGEREF _Toc505457818 h 28
LIST OF FIGURES TOC h z c “Figure” Figure 1: Greater Tzaneen Municipality PAGEREF _Toc507702413 h 5Figure 2: Rainfall variability and irrigation hours (Westafalia and Farm 2) PAGEREF _Toc507702414 h 30Figure 3: Rainfall variability and irrigation hours (Vergelegen and Farm 3) PAGEREF _Toc507702415 h 32Figure 4: Rainfall variability and irrigation hours (New Agatha-BOS and Farm 1) PAGEREF _Toc507702416 h 34Figure 5: Citrus irrigation hours and citrus production PAGEREF _Toc507702417 h 36Figure 6: Rainfall variability and citrus production PAGEREF _Toc507702418 h 38
LIST OF APPENDICES TOC h z c “Appendix” Appendix 1: Figure AA (September-December) PAGEREF _Toc505457866 h 53Appendix 2: Annual Citrus Production Data PAGEREF _Toc505457867 h 54Appendix 3: Citrus Irrigation Patterns PAGEREF _Toc505457868 h 55Appendix 4: Average Rainfall Data for Three Weather Stations PAGEREF _Toc505457869 h 56
LIST OF ABBREVIATIONS AND ACRONYMSCGACitrus Growers Association
CPWF R4DChallenges Program on Water and Food Research for Development
DAFFDepartment of Agriculture Forestry and Fisheries
DEADepartment of Environmental Affairs
FAOFood and Agriculture Organisation
GTEDAGreater Tzaneen Economic Development Agency
GTMGreater Tzaneen Municipality
IPCCIntergovernmental Panel on Climate Change
LTASLong-Term Adaptation Scenarios Flagship Research Program
NACNational Agro-meteorological Committee
PCIPrecipitation Concentration Index
SAWSSouth African Weather Services
ABSTRACTRainfall variability has the potential to adversely affect crop production in the semi-arid regions of South Africa. Citrus production in the Greater Tzaneen Municipality is done under irrigation as well as under natural rainfall. Citrus is vulnerable to rainfall variability. Moisture stress is a limiting factor for citrus production. Irrigation is necessary during dry and low rainfall seasons. The aim of the study was to analyse the influence of rainfall variability on irrigated citrus production in the Greater Tzaneen Municipality. Rainfall statistics of New Agatha-BOS, Westafalia and Vergelegen weather stations for the period 2006-2016 were obtained from South African Weather Services. Three farms linked to the three weather stations provided irrigation patterns and production data. Seasonal rainfall characteristics of Greater Tzaneen Municipality were analysed using the Precipitation Concentration Index (PCI). Using rainfall variability as a predictor, the relationship between rainfall variability and irrigation hours was established using simple linear regression analysis. Results show variable negative significance of the relationship between seasonal rainfall variability and seasonal irrigation hours. Rainfall variability alone does not explain much of citrus irrigation hours. Further, simple linear regression analysis indicated that the relationship between irrigation hours and citrus production was insignificant. Results indicated that irrigation alone does not meet water requirements for citrus crop production. It is concluded that rainfall variability influences citrus production. However, its influence is insignificant indicating the power play of other factors. It is recommended that farmers should not only focus on rainfall variability as the main factor influencing citrus production. They must also consider other factors such as temperature increases, soil fertility, topography and pest infestation among others.
Key Words: Rainfall variability, Citrus production, Irrigation, Moisture, Precipitation Concentration Index
CHAPTER 1: BACKGROUND TO THE STUDY1.1 IntroductionRainfall variability is the degree to which rainfall amounts vary across an area and through time. It is an important characteristic of climate of an area and has two components i.e. spatial and temporal variability (Banchiamlak and Mekonnen, 2010). Department of Agriculture, Forestry and Fisheries (DAFF) (2016) emphasized that rainfall variability has a significant impact on crop production, making it delicate with high chances of crop failure in the semi-arid areas which are already marginal for crop production. Shifts in rainfall and weather patterns are occurring worldwide (Barrios et al., 2008). Agricultural production is sensitive to weather variability with variations in the distribution of rainfall throughout the African continent.
Climate change affects rainfall through rainfall variability which is determined by the hydrological cycle, and observable rainfall patterns (Easterling et al., 2012). Climate change refers to a change in the state of the climate that can be identified by changes in the climate mean and the variability of its properties, and that persists for an extended period, typically for decades or longer (IPCC, 2007). Climate variability impacts negatively on agriculture particularly in the sub-humid areas which are vulnerable to many environmental hazards such as frequent floods and droughts (Zhao et al., 2005). Variations in rainfall have devastating effects in areas where agriculture is predominantly rain fed and hence any irregularity in weather conditions has adverse welfare implications (Meza-Pale et al., 2015). Observations by Allamano et al. (2009) suggest that rainfall variability has significantly impacted on the rural poor who mostly rely on natural rainfall for crop production and land tillage.
World Bank (2010) observed that South Africa has been getting hotter over the past decades, with an increase in the number of warmer days and a decrease in the number of cooler days. Moreover, the country’s average rainfall, estimated at 450 mm per year, is well below the normal average rainfall of 860 mm per year. Evaporation rate is comparatively high (World Bank, 2010). In addition, surface and underground water resources are limited. Agriculture is expected to be the worst affected by these changes because it is highly dependent on climate variables such as rainfall, humidity and temperature (IPCC, 2011).
South Africa’s diverse weather and climatic conditions enable the country to cultivate and produce a variety of fruits (Ntombela, 2013). The country is known globally as a producer and exporter of citrus, deciduous and subtropical fruits. Citrus trees are subtropical in origin and cannot tolerate severe frosts. According to Citrus Growers Association (CGA) (2012) citrus fruit production requires a warmer subtropical environment because they are sensitive to cold climates and trees can die off because of freezing temperatures. However, there are different types of citrus varieties that have sufficient cold hardiness to sustain freezing conditions, especially in mature fruit.
Citrus fruits are categorised as oranges, limes, lemons, grapefruit and kumquat fruit. The citrus fruit list has various cultivars such as navels, valencia’s, clementine’s, mandarins and tangerines (CGA, 2012). These varieties differ in taste, harvesting time and colour. The main citrus production areas in South Africa are Limpopo, Eastern Cape, Mpumalanga, Western Cape and KwaZulu-Natal provinces (CGA, 2012).
Farming citrus under dry land is very difficult (Meza-Pale and Yúnez-Naude, 2015). Citrus production is highly affected by the amount of water received in both current and previous growing seasons (Morgan et al., 2010). When citrus trees do not get enough water, growth rate is reduced, young fruits fall, and mature fruit lacks sugar and its quality deteriorates (Obreza and Schumann, 2010). Vegetative growth is also reduced, limiting the number of new fruit bearing branches. Roots and leaves do not develop properly, thereby affecting the number and size of the fruit and alternative bearing, which is high production one year followed by lower production the next year. Adequate water amounts are important during flowering and fruit set to achieve good production (Shirgure, 2013).
Citrus production is done under irrigation and rain-fed agriculture in South Africa (Potelwa et al., 2016). Dabrowski et al. (2009) point out that moisture is a limiting factor in citrus production because rainfall is often poorly distributed and deficient in most cases. It is necessary to supplement moisture by irrigation during dry and low rainfall seasons to ensure that moisture stress does not supress growth, development and production (Asif et al., 2015). Drip irrigation is the best irrigation system for citrus, with the use of drip fertigation where pH and electricity conductivity are controlled (Shirgure, 2012). The micro-sprinkler and overhead sprinkler irrigation systems are also commonly used (DAFF, 2013). Citrus trees are evergreen and require consistent moisture, and should be irrigated all year-round, especially during active growth periods (Shirgure, 2012). This study seeks to analyse the influence of rainfall variability on irrigated citrus production in the Greater Tzaneen Municipality.
1.2 Problem Statement
Department of Agriculture, Forestry and Fisheries (DAFF) (2016) emphasised that rainfall is not sufficient to meet the water requirements of commercial citrus production in South Africa. Therefore, citrus plantations are irrigated except where severe droughts cause restrictions in the water that is available for irrigation. Zekri (2011) noted that cultural practices that attempt to cope with climatic or weather problems include irrigation and nutrition. Citrus trees require a good water management system and a balanced nutrition program formulated to provide specific needs for maintenance and for expected yield and fruit quality (Zekri, 2011).
Citrus growth and development is greatly affected by rainfall variations. Global climate changes have led to changes in rainfall patterns, rainfall reduction and an increase in dry spells and droughts reducing soil moisture (Mupangwa et al., 2016). Increases in temperature coupled with more rainfall variability due to the changing climate reduce crop productivity. Where most crops are not irrigated, food production will drop. Rainfall is an important variable which have direct and indirect effects on agricultural crops. Rainfall is erratic and unpredictable (Bewket, 2009). Therefore, rainfall variation increases moisture stress in citrus trees, which then affects the productivity. This research seeks to find the extent to which rainfall affects productivity.
1.3 Research QuestionsThe study seeks to address the following questions:
What are the rainfall patterns in the Greater Tzaneen Municipality for the period 2007 to 2016?
To what extent does rainfall variability influence citrus irrigation?
To what extent does rainfall variability affect citrus production?
1.4 Research Aim and Objectives1.4.1 Research AimThe aim of the study is to analyse the influence of rainfall variability on irrigated citrus production in the Greater Tzaneen Municipality.
1.4.2 Research ObjectivesThe specific objectives of this study are to:
examine the rainfall variability of the Greater Tzaneen Municipality for the period 2007 to 2016.
establish the influence of rainfall variability on citrus irrigation patterns.
assess the influence of rainfall variability on citrus production.
1.5 Delimitation of the Study and Study Area
1.5.1 Focus of the StudyThe study analysed the influence of rainfall variability on irrigated citrus production in the Greater Tzaneen Municipality. The study focused on the relationship between rainfall variability and irrigated citrus production. This is because rainfall is an important element for crop production. Therefore, it is difficult for plants to reach maximum possible productivity without adequate rainfall. The study was limited to irrigated citrus crops. The researcher sought to find out if variations in rainfall affect the productivity of irrigated citrus crops.
1.6.2 Description of the Study AreaAccording to Mopani District Report (2007) the Greater Tzaneen Municipality (GTM) is situated in the eastern quadrant of Limpopo province under the Mopani District Municipality, located within 23.8683° S and 30.0665° E. GTM covers an area of 3 243km2, it is bordered by Greater Letaba to the north, Lepelle-Nkumi to the south, Ba-Phalaborwa and Maruleng to the east and Polokwane to the west. GTM contains 125 rural villages, with almost 80% of households residing in these villages. The area includes the towns of Tzaneen, Nkowankowa, Letsitele and Haenertsburg (Mokgalabone, 2015).
The Greater Tzaneen Municipality is characterized by extensive and intensive farming activities and considered untapped tourism potential. The main economic sectors in the GTM are community services (31.7%), finance (23.8%), trade (10.2%), agriculture (7.6%) and manufacturing (3.7%) (Mopani District Report, 2007). The municipality is currently engaged in developing the tourism sector and has established a tourism centre to provide information about tourism attractions (GTEDA, 2010).
Indigenous and exotic plants are found in the subtropical area of the Greater Tzaneen Municipality. The area lies at the foot of the Northern Drakensberg Mountain in the heart of a forestry area and in South Africa’s richest sub-tropical fruit farming region (GTEDA, 2010). The valley of Tzaneen yields valencia oranges and grapefruit such as star ruby. Macadamia nuts are also a common crop in the area, with the town producing most of the country’s mangoes, bananas, avocados, pears, paw-paws, tea and coffee. Letsitele is the main citrus production area in the GTM. The Greater Tzaneen Municipality also contributes substantially to the total production of timber, citrus and litchis (GTEDA, 2010). GTM is enriched with fertile land and natural resources. Farmers around the area entirely depend on the Letaba River for irrigation purposes.
Figure SEQ Figure * ARABIC 1: Greater Tzaneen Municipality1.7 Justification for the Study
The Greater Tzaneen Municipality was selected because it is one of the major citrus growing areas in Mopani District Municipality in Limpopo Province (DAFF, 2013). The effects of rainfall variability have been felt in many regions in South Africa thus leading to low food production and death of livestock in humid and semi-arid regions (DAFF, 2013). This study provides an understanding of the relationship between rainfall variability and irrigated citrus production. Results inform farmers trying to improve their irrigation practices. Rainfall variability analysis provides detailed information to farmers in the area regarding adaptation to changes in rainfall patterns and trends. The study contributes to the larger food insecurity cause brought by rainfall variability.
1.8 Definitions of the Key TermsAgriculture: The growing of crops, the raising of livestock, and the utilisation of forestry and fishery resources (Lehohla, 2011).
Citrus: A common term and genus of evergreen flowering plants in the rutaceae family, plants in the genus produce citrus fruits, including important fruits like oranges, lemons, grapefruit, pomelo and limes (Keogh et al., 2010).
Climate change: A change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods (Protocol, 1997).
Precipitation Concentration Index: Analyses the heterogeneity of precipitation and the relationship between variability and distribution of monthly precipitation (Zhao et al., 2011).
Rainfall Variability: The degree to which rainfall amounts vary across an area or through time, it is an important characteristic of the climate of an area and has two components i.e. spatial and temporal variability (Banchiamlak and Mekonnen, 2010).
Irrigation: The essentially artificial application of water to overcome deficiencies in rainfall for growing crops (Cantor, 1970).
1.9 Chapter Summary
Rainfall variability is occurring worldwide due to climate variability as a result of the changing global climate. Rainfall is unpredictable and agricultural production is sensitive to rainfall variability. Areas where crop production is rain fed, rainfall variations have devastating effects which threatens the progress and effort made in accelerating agricultural crop production. Citrus production is highly affected by rainfall variability. In South Africa, citrus is done under irrigation, especially in the Greater Tzaneen Municipality in Limpopo Province which is one of the main citrus growing areas in the country. Moisture is a limiting factor for citrus crops and therefore irrigation is necessary during insufficient rainfall seasons to meet the crop’s water requirements which affect the productivity. The next chapter shows how rainfall variability influences citrus production by reviewing related literature from various scholars.
CHAPTER 2: LITERATURE REVIEWAccording to IPCC (2011) the scientific community widely agree that climate change is a reality. This chapter aims to place the study under scholarly context by reviewing various contributions made by several authorities and researchers on rainfall variability and citrus production. This chapter will review related literature on the influence of rainfall variability on crop production. It is precisely focused on what other scholars have done and their findings. This enables the researcher to put the problem in its right perspective and hence, provide a better understanding and appreciation of the problem under investigation. Issues and concepts of rainfall variability and citrus production are theoretically and empirically reviewed.
The chapter contains the following sub sections; Climate and Weather Variability, Rainfall Trends and Change, Rainfall Seasonality, Rainfall Variability in Limpopo Province, Irrigation and Rainfall, Rainfall Variability and Citrus Yields, Rainfall Variability and Crop Production, Precipitation Concentration Index and Rainfall Variability Adaptation Strategies.
2.1 Climate and Weather VariabilityThe world’s climate is continually changing at rates that are projected to be extraordinary in recent human history. According to IPCC (2012) most of the observed increase in the global average temperature since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations. When the climate changes and variability occur, there is high possibility of damages, danger or disaster to mankind. Events such as droughts, floods, storms and hurricanes, and spells of extremely high or low temperatures are recognised as major risks associated with climate change and variability (Kazoka, 2013).
Long term changes in the patterns of climatic variables such as rainfall and temperature are referred to as climate variability (Ngaira, 2007). It is the variation around the average climate, including seasonal variations in atmospheric and ocean circulation such as the El Nino. According to Orindi and Murray (2005), climate variability is the shift from the normal experienced rainfall pattern of seasons to abnormal rainfall patterns. Climate variability can therefore be thought of as a long-term summing up of weather conditions, taking account average conditions and variations including fluctuations that occur from year to year, and the extreme conditions such as rigorous storms or unusually hot seasons (Nations, 2010).
Long-term climate change influence global food production. Extreme weather events and their year to year variability pose a great risk to food security globally (Karanja, 2014). Historically, reductions in crop productivity have been attributed to low rainfall events. However, even small changes in mean annual rainfall can impact on productivity. Lobell and Burke (2008) reported that a change in growing seasonal rainfall by one standard deviation can be associated with as much as 10% change in production for example millet in South Asia.
Asada and Matsumoto (2009) analysed the relationship between district-level crop yield data (rainy season ‘kharif’ rice) and precipitation for 1960–2000. It was shown that different regions were sensitive to rainfall extremes in different ways. Crop yield in the upper Ganges basin is linked to total rainfall during the relatively short growing season and is thus sensitive to drought (Karanja, 2014). Equally, the lower Ganges basin was sensitive to pluvial flooding and the Brahmaputra basin demonstrated an increasing effect of rainfall variability on crop yield particularly for drought. These relationships were not consistent through time, in part owing to rainfall trends. Variation between districts implied the importance of social factors and the introduction of irrigation techniques (Karanja, 2014).
Weather refers to the atmosphere’s evolution over short periods of time (Auffhammer et al., 2013). Weather and climate variability impose a wide range of direct and indirect impacts on crop production hence, weather fluctuations play a significant role in crop growth and yield. Any change in local weather conditions, especially during critical developmental stages of crops, may adversely impact growth processes and result in enormous yield reductions (Karanja, 2014). This situation makes climate variability a threat to food production with potentially serious economic implications at local, regional, national and global scales.
Weather variability is already exerting control over development progress, including efforts to address food security and poverty alleviation in sub-Saharan Africa (Sokona and Denton, 2001). On many occasions, extreme events of weather variability leave people vulnerable in Africa and indeed in other regions of the world totally unprepared and unable to cope (Karanja, 2014). The adverse impact of climate change is further visualized on natural resources such as water and land. These resources are threatened by poor and unsustainable resources management, on one hand and the impact of weather variability on the other. Agriculture in Africa is a weather dependent activity and is most vulnerable to climate change and its effects (Ehiakpor et al., 2016).
2.2 Rainfall Trends and ChangeDepartment of Environmental Affairs (DEA) (2015) opine that the mean annual rainfall in South Africa is highly variable, making it impossible to identify trends over the past five decades with statistical confidence. This is also true for global rainfall trends, which show statistically significant trends of increasing rainfall only at mid-latitudes in the northern hemisphere. DEA recently analysed trends in 2013 rainfall metrics in South Africa. The analysis used data from 72 South African Weather Services (SAWS) weather stations, of which less than 20% of the data is missing for the 1960–2000 period (DEA, 2015). Overall, trends in rainfall totals are not significant, although there is a tendency towards a decrease in the number of rain days. There is also evidence of increasing trends in rainfall totals over South Africa’s central interior, and an increase in extreme rainfall events, especially in spring and summer over the central interior (DEA, 2015). This is accompanied by a reduction in extremes in autumn. These results are consistent with those obtained by independent researchers.
There is less certainty about rainfall trends than temperature trends, with a range of studies using different models producing different results. The Department of Environmental Affairs (2015) emphasized that South Africa’s adaptation response consequently needs to be vigorous to this critical uncertainty and aim for low-regret or no-regret interventions to retain flexibility for an appropriate response to any long-term trend that might emerge.
Anticipated changes in rainfall totals and other rainfall-related statistics generated by global climate models are more uncertain than temperature change projections. This is because global climate models simplify several aspects of the climate system relating to rainfall, including topography, convective rainfall processes, and processes of cloud formation and dynamics (DEA, 2011). In addition, some fundamental processes relating to moisture transport are inadequately captured, decreasing confidence in convective processes and related rainfall processes. These are of relevance for rainfall in tropical latitudes.
Global climate models may not reproduce local scale or regional scale rainfall patterns accurately and often produce significant biases, too much rainfall or too little rainfall in comparison with observations. Even so, global climate models can reproduce large-scale circulation features well and, in many cases, agree on projected shifts in these large-scale processes into the future (DEA, 2011). For this reason, consideration should be given to large-scale shifts in rainfall patterns produced by global climate models rather than to local-scale changes, and to the investigation of downscaling approaches with full presentation of uncertainties to gain insights into local-scale precipitation changes because of large-scale circulation changes (DEA, 2015).
Up to 2035, models show mixed, relatively small and insignificant changes in annual total rainfall across South Africa. Towards mid-century, many models show significant changes, with many models showing decreased rainfall, especially in south-western South Africa, and a few showing increased rainfall in various regions, particularly in the summer rainfall region (DEA, 2015).
2.3 Rainfall SeasonalitySouth Africa has a range of seasonal rainfall regimes in respect to its variability and rainfall, with winter rainfall in the southwest, summer rainfall in the northeast, and an intermediate seasonality in between (DEA, 2011). This seasonality is important for economic activities and is also important for understanding extreme weather events. It is difficult to identify clear changes in future statistics of extreme weather events. Large-scale circulation changes indicate that extreme winter flooding events may occur less frequently over the southern parts of South Africa in response to a pole ward displacement of the frontal systems that bring winter rainfall (DEA, 2011). Tropical cyclone tracks are projected to shift northward in the summer rainfall area, bringing more flood events to northern Mozambique and fewer to the Limpopo Province in South Africa
Climate change is becoming increasingly apparent in Limpopo (DEA, 2015). Eighty per cent of South Africa experiences predominately summer rainfall, 10% winter rainfall and less than 10% rain throughout the year (Southern coastal region). The seasonality and high unreliability of rainfall results in dry periods during which the food security problem increases for many households and agricultural sectors (Tadross and Johnston, 2012). Droughts are experienced on average in every 3 out of every 10 years. Increase in temperatures and changes in rainfall pose the greatest threat to agriculture and water supplies in the region. Crop suitability and yield are both expected to change in the future and adaptation options must include alternatives and demand reduction in the case of water (Tadross and Johnston, 2012).
Information about rainfall patterns and variability is provided by the analysis of rainfall records for long periods (Lázaro et al., 2001). Stephens (1974) and Edwards et al. (1983) observed that rainfall is not necessarily distributed except in wet regions. Jackson (1977) emphasized that annual rainfall distributions are markedly skewed in semi-arid areas and the assumption of normal frequency distribution for such areas is inappropriate.
According to Ford et al. (2015) Limpopo faces a warmer and potentially hotter future. In terms of rainfall, available science is less definitive while some models project decreased rainfall over Limpopo in the long term. These rainfall projections remain within the realm of present-day variability. However, other models suggest that there may be future increases in rainfall in the region, exemplifying the uncertainty in model projections for this region of Southern Africa within the existing body of knowledge. However, what emerges out of such uncertainty is that the region is likely to experience greater variability in rainfall and will almost certainly witness an increase in evaporation rates, implying a drier future even in the presence of greater rainfall and heavy rainfall events (Ford et al., 2015).
2.4 Rainfall Variability in Limpopo ProvinceRainfall variability is the variations in rainfall from place to place or the variations in rainfall between years (Obeng, 2014). Rainfall in South Africa is highly variable in the distribution and amount from year to year as well as from region to region. The average rainfall of South Africa is 450 mm compared to a global average of 860 mm, but large and unpredictable variations are common (DAFF, 2013). The variability of rainfall increases from east to west and corresponds with decreasing rainfall in most cases.
Rainfall in Limpopo Province ranges from 200 mm to 750 mm per annum. Typically, 200 mm in the hot dry areas to 1500 mm in the high rainfall areas, with most of it happening between October and April (DAFF, 2013). The Greater Tzaneen Municipality is in the steppe veld of the province and receives most of its rainfall during the summer. Rainfall in the province varies significantly between years. There has been a perceptible decrease in the total rainfall on much of the eastern part of Southern Africa including much of the Limpopo River Basin (Malherbe et al., 2012). This can have serious impacts on the water balance of the region, affecting the largely rural population that depend on agriculture.
The Department of Environmental Affairs (2015) shows that there is a decrease in summer rainfall, decreased productivity of food crops, and increased crop irrigation requirements due to increased temperatures in the Limpopo Province. The Limpopo Province is the most vulnerable province to climate change in South Africa. Besides expecting strong variations in rainfall patterns and greater frequency of extreme events, the province is very susceptible as it already faces multiple pressures from poverty, inadequate housing and poor access to services to name a few (DEA, 2015).
According to Tadross and Johnston (2012) changes in rainfall are typically harder to detect due to its greater variability, both in space and time. Even so, changing rainfall patterns have been detected for many parts of the globe, including moderate decreases in annual rainfall over Southern Africa. Rainfall variability is expected to have a significant adverse effect on countries where agriculture is the main economic activity (IPCC 2014). Because of climate variability, a significant shift in the pattern of rainfall distribution is expected to occur in the coming decades (IPCC, 2007). The shifts in the amount and intensity of rainfall are also projected to affect agricultural productivity, land suitability and welfare levels of households which derive their livelihood from agriculture (IPCC, 2007).
Rainfall variability affects mainly rain-fed, traditional, marginal, low-input using agriculture in developing countries and thus, the loss in crop productivity further worsen already difficult food security situations (Ching et al., 2011; Knox et al., 2012). Rainfall variability further widens income inequality, food insecurity, and malnutrition among the world population. Its impact on agriculture and hence food production is complex. Thus, rainfall variability directly affects food security by altering agro-ecological conditions and indirectly by retarding growth and altering the distribution of income (Hanjra and Qureshi, 2010).
Rainfall variability has a significant negative effect on the overall economic performance of many African countries in general (Sultan et al., 2014) and Sub-Saharan Africa. Sub-Saharan African is characterized by subsistence agriculture, rampant food insecurity, poverty, low rate of irrigation uses and low productivity (Knox et al., 2012).
2.5 Irrigation and RainfallClimate factors like rainfall influence the availability of irrigation water because irrigation depends on rainfall for recharge (Obembe et al., 2015). Agricultural production is not totally dependent on rainfall. Irrigation is still affected by climate variables. High temperatures result in greater evaporative losses from dams as well as from the ground surface (Hart et al., 2013). With higher temperatures, more irrigation will be required for agriculture. Climate change projections indicate that both temperature and evapotranspiration are likely to increase the incidence of drought potential even if total rainfall of an area increases into the 21st century (Van Jaarsveld, 2001).
Irrigation is an age-old method of increasing agricultural productivity. It expands the arable area, improves yield and increases cropping frequency. Irrigation reduce dependency on rain fed agriculture in drought prone areas and increase cropping intensities in humid and tropical zones by extending the wet season and introducing effective means of water control (FAO, 2014). Perret (2002) indicated that at present, South Africa has an estimated 1.3 million hectares of land under irrigation for both commercial and subsistence agriculture.
According to Ezekiel et al. (2012) irrigated agriculture is one of the most critical human activities sustaining civilization. The current world population of 6.8 billion people is sustained in a large part by irrigated agriculture. Irrigation has been described as a necessary solution to insufficient rainfall and poor distribution of rainfall in agricultural areas (Punial and Pande, 1979). Similarly, Daniel (1990) observed dry conditions due to evaporative demand of the atmosphere which continuously create stress for plants and therefore require water supplements for the period. Irrigation projects are designed to help reduce the dependence of crop growth on rainfall, which is uncontrollable by man. Adoption of irrigation in such areas had ensured improved harvest and encouraged crops diversification
Irrigation is responsible for about 72% of global and 90% of developing country water withdrawals (FAO, 2013). Around 80% of the world’s agricultural land is rain fed which contributes at least two-thirds of global food production (Alam et al., 2011). At the same time, irrigation plays an important role in supplying food. About 20% cropland of the world is irrigated, with a major fraction located in Asia, producing about 40% of the global crop yield annually (Newton, 2007).
Irrigation plays a significant role in poverty reduction and leads to increased yields, increased cropping areas and higher values either by raising employment, cutting prices in an imperfectly open economy or if there are high transport costs. Yields boosting by irrigation can mean increased food supplies which lead to better nutrition levels. Irrigation can also help to reduce adverse consequences of drought (Majoro et al., 2016). Dowgert and Fresno (2010) opine that environmental risks associated with farming are mitigated through irrigation. Large investments on irrigation are made by farmers in drought prone areas. The risk mitigation provided by irrigation goes beyond simple economic advantage to the farmer. Irrigation allows for a more consistent food supply and higher productivity.
Lankford et al. (2016) indicated that irrigation secures crop productivity against short falls or breaks in rainfall. Irrigated crops often enjoy a cash margin and with more water, crop productivity increases profitable levels. Security of water improves the planning and timing of start of cropping season and can extend the season’s length (Sambo, 2014). Irrigation raises the number of paid jobs conducted on the land, for example, irrigation and weeding. To reduce the risks associated with rainfall variability and to increase the yields of food crops, more public investments in yield-enhancing technologies such as small-scale irrigation and irrigation management systems have been recommended as one important rural development and poverty reduction strategy (Sambo, 2014).
Lawston et al. (2015) emphasized that in humid regions, the amount of water to apply and the irrigation frequency are strongly influenced by seasonal rainfall. One of the greatest challenges to irrigation scheduling in North Carolina is efficiently and effectively supplementing rainfall. During periods when no rainfall occurs, 1 inch of irrigation water may be required every three to four days. During a season when rainfall occurs frequently, irrigation may be needed only once or twice a month. In most years, the need for and frequency of irrigation falls between these extremes (Lawston et al., 2015).
According to Department of Environmental Affairs (2013), Long-Term Adaptation Scenarios Flagship Research Programme (LTAS) the South African agricultural sector is highly diverse in terms of its activities and socio-economic context. Only 14% of the country is currently considered potentially arable, with only one fifth of this land having high agricultural potential. Overall, many agricultural sub-sectors are sensitive to projected climate change. Certain crops grown in South Africa tolerate extreme climatic events, for example groundnuts, sorghum, while others are sensitive to heat, for example, maize and, tomatoes. Similarly, climate change impacts for some crops can be projected with more confidence than others (DEA, 2013). The smallholder and subsistence dry land farmers are more vulnerable to climate change than commercial farmers. While large-scale irrigated production is probably least vulnerable to climate change, it is conditional to sufficient water supply for irrigation being available (Schulze, 2010; DAFF, 2013).
2.6 Rainfall Variability and Citrus YieldsExtreme climatic conditions and high inter-annual or seasonal variability of climate parameters can adversely affect productivity (Li et al., 2006). This is because rainfall governs crop yield and determines the choice of crops that can be grown. The pattern and amount of rainfall are among the most important factors that affect agricultural systems (Mzezewa et al., 2010). The analysis of rainfall records for long periods provides information about rainfall patterns and variability (Lázaro et al., 2001). Variations in citrus yields depend on rainfall variability in the Greater Tzaneen Municipality, as rainfall is the main source of water for crop growth (DEA, 2013). Most agricultural areas in the Greater Tzaneen Municipality are rain-fed and irrigated.
Chelong and Sdoodee (2013) state that environmental variables especially rainfall, are the key factor which affects plant growth, development and productivity. Differences in the development, yield and quality of fruit attributes in varying seasons and locations might be due to the different climatic conditions that are based on the rainfall prevailing during the crop life cycle (Chelong and Sdoodee, 2012). Climate is interrelated with citrus quantity and quality in the subtropical region, the fruit growth rate is rapid, but the fruit quality of oranges and mandarins is poor, with peel colour typically green and the juice colour a pale, light yellow (Davies and Albrigo, 1994; Makinde et al., 2011).
Citrus is an important subtropical evergreen economic fruit in South Africa. The most citrus production takes place in the Limpopo province at 31% (18 146 ha). Citrus production is largely dependent on climatic conditions which can only be partially manipulated by man through irrigation (DAFF, 2016). Distinct differences in climatic conditions affect different growth periods, and there is also a significant relationship between yield and climate conditions (Duane et al., 2010). Moisture is a limiting factor in citrus production. Because rainfall is often poorly distributed and, in most cases, deficient, it is necessary to supplement moisture by irrigation to ensure that moisture stress does not suppress growth and production. Rosenzweig et al. (2002) examined the potential impacts of weather variability on citrus production.
Water is vital to plant growth, so varying rainfall patterns have a significant impact on agriculture. As over 80% of total agriculture globally is rain-fed, projections of future rainfall changes often influence the magnitude and direction of climate impacts on crop production (Karanja, 2014). A climate with moderate rainfall and sunshine is good for citrus trees. It promotes good flower differentiation, flower and fruit quality and development. High-rainfall areas are less suitable for citrus (CGA, 2012) because they have higher pest and disease burden, lower yields and poor fruit quality. Citrus growers consider rainfall distribution, rainfall intensity, duration and frequency.
2.7 Rainfall Variability and Crop ProductionRainfall variability is significantly associated with variation in agricultural output across geographic regions and time (Thornton et al., 2014). Rainfall variability is expected to have a significant adverse effect on countries where agriculture is the main economic activity (IPCC 2014). Changes in the average rainfall patterns is predicted to lead to high and very high risk of severe and irreversible impacts globally by the end of the century (IPCC, 2014).
The Department of Environmental Affairs (2013) emphasized that the projected change in the amount of rainfall is likely to negatively influence crop yields. Yield losses at mid-century range were estimated to be more than 30% (Schlenker and Lobell, 2010). A series of climate projections suggested that South Africa faces a considerably drier and warmer future by 2050 with projected rainfall decreases by more than 40 mm per year for large parts of the interior for the 2080-2100time period (DEA, 2013). Studies of precipitation data reports an increase in rainfall fluctuations in South Africa since 1960 (Fauchereau et al., 2003; Kane, 2012).
Observed trends in daily minimum and maximum extreme temperatures during 1962-2009 reveal stronger increases in heat extremes in many regions (Kruger and Sekele, 2013). A higher frequency of flooding and drought extremes is also projected with the range of extremes exacerbated significantly if the global emissions are not constrained (DEA, 2013). In 2015 – 2016 South Africa was suffering the worst drought since 1982, which resulted in a devastating drop in food and rising prices of staples such as corn and low-income households were affected the most (Willemse et al., 2015).
Fruit and vegetable production is influenced by climate variability in rainfall availability (Johkan et al., 2011). Rainfall has a direct relationship with agricultural crops with an increase or decrease in precipitation having impact on yield (Walthall et al., 2013). Kassie et al. (2014) suggested that rainfall variability does not affect crop yields directly on water availability but indirectly affect crop yield by limiting the application of agricultural inputs (e.g. fertiliser). For instance, corn is vulnerable to excess water in the early growth stages and can cause a reduction in plant growth, while a reduction in the amount of water in soil leads to less growth and yield if the stress occurs during the grain filling period of growth (Hatfield and Prueger, 2015).
The study by Awotoye and Matthew (2010) on the effects of temporal changes in climatic variables on crop production in Nigeria reveals a decrease in yield of sorghum in the year 2000 when rainfall reduced. However, as the amount of rainfall increased in 2002 and 2004, the yield of maize increased. This gives an indication to the effect that increases or decreases in rainfall has a greater propensity of determining the yield of crops especially, grains.
The IPCC uniform climate scenarios show that a decrease in rainfall in a place will cause a reduction in yield with farmers losing their entire net revenue from crops if rainfall decreases by 14% (Kassahun, 2009). Similarly, the study of Molua and Lambi (2006) shows a decrease in net revenues when rainfall decreases, or temperature increases across farms in Cameroon. The forgoing studies give credibility to the fact that rainfall influence crop production. While an increase in rainfall causes an increase in crop yield, a reduction in rainfall causes a decline in the net yield of crops. Especially, crops that need considerable amount of water to survive (Karanja, 2014). There is therefore a direct relationship between rainfall and crop yield. Therefore, in the event of low rainfall, there is need to resort to irrigation to ensure that crops get the needed amount of water for their growth.
It is important to recognise the fact that, despite the impacts climate variability has on crop production, there are some positive effects as well. For instance, Sudarkodi and Sathyabama (2011) opine that the high concentration of atmospheric carbon dioxide which is believed to cause warming conditions and affect crops rather increases photosynthetic activities of crops and increase yield. According to them, the doubling of carbon dioxide increases photosynthetic rate by as much as 30 to 100%. Again Lee et al. (2012) attest that high temperatures and very high rainfall in summer increases agricultural production. Even though the dynamics of how high temperature may lead to crop increase is not clear, it is quite clear that an increase in rainfall may lead to an increase in yield especially with crops that need a greater amount of rainfall like rice.
According to Musetha (2016) the National Agro-meteorological Committee (NAC) Advisory on the 08 DAFF 2011 report indicates that from 2010, Limpopo received normal rainfall in average, except in areas around Vhembe, Mopani and Lephalale Municipalities where below normal rainfall was experienced. Crops were in a poor condition due to high temperatures and insufficient rainfall during the critical stage of growth, especially for farmers who planted late (Musetha, 2016). The average dam’s level in Vhembe was 81% in 2011 as compared to 87% of 2010 during the same period. The rest of the dams across the province were at satisfactory levels apart from Middle-Letaba (5%); Nsami (34%) and Albasini (41%) dams (Musetha, 2016).
According to Magombeyi et al. (2013), CGIAR Challenge Program on Water and Food Research for Development (CPWF R4D) rainfall in the Greater Tzaneen is highly seasonal and unevenly distributed spatially, with about 95% of the rains occurring between October and April, typically concentrated in several isolated rain days in isolated locations. Rainfall also varies significantly from year to year (Magombeyi et al., 2013). These rainfall characteristics limit crop production because annual rainfall mainly occurs over a short summer rain season with high inter-annual variations. Flooding and droughts are major Agricultural Production -mediated impacts of climate change in the Limpopo Province and it is known for its livestock farming in the northern drier parts, timber plantations in the southern area, The Kruger National Park in the east, and its fruit industry in the central zone, where Greater Tzaneen Municipality is located (Magombeyi et al., 2013).
An increase in temperature and a decrease in rainfall will stress crop production. Consequently, the demand for water will rise. Moreover, rainfall variability affects agriculture through reduced rainfall and increased evapotranspiration as an indirect result of a change in climatic variables other than the direct impacts on temperature and rainfall (Bocher, 2016). As crop production and productivity are a function of climatic and environmental variables, this is particularly worrying since agriculture in most developing countries is highly exposed to climate shocks and the over reliance of production activities on climate-sensitive sectors (Bocher, 2016).
2.8 Precipitation Concentration Index
Precipitation concentration index (PCI) was proposed by Oliver in 1980. The PCI is a powerful indicator of the temporal distribution of precipitation, traditionally applied at annual scales. As the PCI value increases, the more concentrated the precipitation. The PCI expresses the seasonal and annual variability of precipitation in percentage. The low values of PCI indicate a uniform distribution of precipitation during the year. However, high values represent either high concentration of monthly rainfall or seasonality (De Luis et al., 2011).
Rainfall is changing due to global warming at both global and regional scales. Future climate changes may involve modifications in climatic variability as well as changes in averages (Alam and Sarker, 2010). Precipitation totals on annual, seasonal or monthly scales are key elements affecting water availability, but precipitation concentration in time also plays a decisive role. In this respect, there are some upfront indicators to evaluate the precipitation concentration that can be used to provide information on its variability and to analyse and understand hydrological processes. The Precipitation Concentration Index (PCI) provides information on long-term total variability in the amount of rainfall received within an area (Alam and Sarker, 2010).
2.9 Rainfall Variability Adaptation Strategies
According to IPCC (2013) adaptation means anticipation of the adverse effects of climate and taking appropriate action to prevent or minimise the damage they can cause or taking advantages of the opportunities that may arise. Farmers can limit the adverse effects of climate change by practicing different adaptation strategies. Yields vary according to soil type, agricultural practice and the type of rainy season (Sanfo et al., 2017). The most prominent adaptation strategies during climatic shocks are changes in farming calendar, selling of livestock, changing crop varieties, integration of crops, practicing soil and water conservation activities, using improved agricultural inputs, and irrigation (Deressa et al., 2012). However, these adaptation strategies are not free of cost or easily available (Robinson et al., 2013).
Many rural communities in sub-Saharan Africa face challenges in selecting appropriate adaptation strategies in response to climate change impacts including high inter-annual rainfall variability and unpredictability of rainfall patterns (Joshua et al., 2016). In the Sahel region, such strategies include adoption of drought tolerant crops such as sorghum, staged sowing and use of hand-dug wells for irrigation during prolonged drought periods. However, it was noted that the farmers in the Sahel were often unaware of the overall scale of clime change impacts, thereby threatening their ability to sustain their family’s livelihood (Joshua et al., 2016).
In semi-arid areas of Tanzania, community-based adaptation strategies included fast-maturing crop varieties, buying supplementary foods, increasing wetland cultivation and livestock keeping, water harvesting, practicing mixed cropping and increased emphasis in small stock (Kangalawe and Lyimo, 2013). The study by Kangalawe and Lyimo (2013) observed that the vulnerable communities often implemented these adaptation strategies on an ad hoc basis with limited planning.
The main barriers cited by farmers in South Africa are lack of access to credit (Bryan et al., 2009). Factors influencing farmer’s decision to adapt include wealth, government support, access to fertile land, access to extension and credit. Rapid warming amplified by El Nino conditions in 2015 and 2016 has removed any illusions that global warming trends have abated. Adverse effects including lack of rainfall in some regions, excessive rainfall in others, novel diseases, ecosystem damage and crop failures reveal a world already showing the human and socioeconomic costs of inadequate preparation for climate change impacts (DEA, 2015).
2.10 Chapter Summary
Reductions in crop productivity have been attributed to low rainfall events. Rainfall seasonality is important for understanding extreme weather events. However, rainfall projections are uncertain, with a range of studies using different models producing different results, changes in rainfall patterns are hard to detect due to its greater variability. Citrus production is not totally dependent on rainfall, irrigation is necessary to supplement the insufficient rainfall. Different adaptation strategies such as irrigation and integration of crops can limit the adverse effects of rainfall variability.
CHAPTER 3: RESEARCH METHODOLOGYThis chapter illustrates the tools employed to achieve the objectives of this study. Quantitative research methods were utilized for the collection and presentation of data. Secondary data was used and obtained from government records such as South African Weather Services and records from farm owners. This chapter includes the research design, data collection methods and data analysis methods.
3.1 Research Design
The research took a case study approach by studying the Greater Tzaneen Municipality within Mopani District in the Limpopo Province of South Africa. Secondary data on monthly rainfall and annual citrus production was collected. The study needed vital rainfall, irrigation practices and citrus production statistics from relevant government departments and farm records from 2007-2016 to analyse the influence of rainfall variability on irrigated citrus production in the Greater Tzaneen Municipality. Table 1 shows the research matrix with objectives, research questions, required data, data sources, data collection and analysis methods and methods used in presentation of results.
Table SEQ Table * ARABIC 1: The Research MatrixObjectives Research
Method Data Analysis Method Results
the rainfall variability
of the Greater
(2007-2016) What are the rainfall
data for 3
stations (New Agatha-BOS, Westafalia & Vergelegen) Seasonal rainfall
PCI (Oliver, 1980)
Annual rainfall ÷ Flowering, growth & maturity seasons Tables
the influence of
rainfall variability on
patterns To what extent
hours (dry, wet & dry-wet
seasons) Farms Weekly citrus
(dry, wet & dry-wet
seasons) Simple linear regression
Seasonal rainfall totals & Seasonal irrigation hours Scatter plot
the influence of rainfall
production To what extent
(2007-2016) Farms Annual citrus
data Simple linear regression
Annual citrus production & annual irrigation hours
Annual citrus production & annual total rainfall Scatter plot
3. 2 Data Collection Methods
Secondary data was collected to address the objectives of this study. Monthly rainfall data for Westafalia, Vergelegen and New Agatha-BOS weather stations was obtained from South African Weather Services to examine rainfall variability. Rainfall data for the period 2006-2016 was used to calculate the Precipitation Concentration Index (PCI), which gives the extent of rainfall variability of the study area. PCI is used as an indicator of the rainfall variability and to describe the rainfall characteristics of Greater Tzaneen Municipality.
Monthly citrus irrigation hours for the dry, wet and dry-wet seasons was obtained from Farm 1, Farm 2 and Farm 3 selected within the study area, to establish the water requirements needed for citrus fruit bearing trees for each season. The data collected was used to establish the influence of rainfall variability on citrus irrigation patterns, this was obtained by regressing the seasonal rainfall totals against the seasonal citrus irrigation hours.
Due to the confidentiality of production data farm names will not be mentioned. Each of the three farms will be identified with a number and is linked to a weather station. Farm 1 is linked to New Agatha-BOS, Farm 2 is linked to Westafalia while Farm 3 is linked to Vergelegen weather station. Annual citrus production data for the period 2007-2016 was obtained from Farm 1, Farm 2 and Farm 3 selected within the study area. Annual citrus production data was regressed against the annual irrigation hours, annual citrus production data was also regressed against the annual total rainfall data to assess the influence of rainfall variability on citrus production.
3.3 Ethical ConsiderationThe participants farms and their names are not mentioned due to the confidentiality of production data. All the information collected for this research is used for academic purpose only.
3.4 Data Analysis
3.4.1 Seasonal Rainfall VariabilityThe annual rainfall data was divided into three periods, which are the flowering, growth and development and maturity or harvesting seasons based on the citrus crop calendar. The three periods were divided to justify the importance of precipitation on the life cycle of citrus fruit crops. During the flowering period in early spring a high amount of precipitation is required for maximum flowering because it is the dry-wet season, moisture stress during flowering could result in excessive drop of flowers and fruitlets (De Villiers and Joubert, 2006). The November-Drop which is the last fall out of citrus fruitlets is during the beginning of the wet season and the start of the growing and development period, therefore precipitation during this period is crucial for the quality and quantity of citrus productivity. Moisture stress during the growing and development period could result in acidic fruits (De Villiers and Joubert, 2006). The maturity or harvest period of citrus crops begins during the dry winter season where there is little or no precipitation which reduces the risk of citrus fungus infections (Vacante and Gerson, 2012).
The seasonal rainfall characteristics of Greater Tzaneen Municipality was analysed through the Precipitation Concentration Index. The Precipitation Concentration Index (PCI) is a tool that is used to determine annual or seasonal rainfall variability. The PCI was applied to examine the seasonal rainfall distribution from 2007-2016 in the study area. PCI represents rainfall variability for each cropping season and shows the characteristics of the seasons (Oliver, 1980). The following equation was used to calculate the seasonal rainfall distribution:(Oliver, 1980)
PCI = Precipitation Concentration Index
Pi = Monthly precipitation in month i
The PCI is interpreted as shown in Table 2.
Table SEQ Table * ARABIC 2: Precipitation Concentration IndexPCI INTERPRETATION
<10 Uniform precipitation distribution (low precipitation concentration)
11-15 Moderate precipitation concentration
16-20 Concentrated (irregular distribution)
21-50 Highly concentrated (strong irregularity)
>50 Isolated (irregular)
Uniform distribution describes the even distribution of rainfall throughout a given period. A moderately concentrated distribution describes the average variation in rainfall distribution throughout the season. Concentrated PCI indicates that rainfall was received during a few months of the season. Isolated indicates an irregular form of rainfall distribution where no pattern can be discerned.
3.4.2 Rainfall Variability and Irrigation PatternsCitrus irrigation patterns in the Greater Tzaneen Municipality are generally constant. However, for the days where rainfall received was above 20 mm farmers did not irrigate for the next 2 days starting on the day after the rainfall, because rainfall received is effective (20 mm) for citrus crops and will stay in the soil for the next 2 days keeping the soil moist. For this reason, the researcher looked at rainfall data for each day of the yearly calendar where rainfall was above 20 mm and subtracted the irrigation hours for the next 2 days on that week. This made the results of the irrigation patterns inconsistent.
The study adopted simple linear regression analysis to establish the influence of rainfall variability on citrus irrigation patterns. Seasonal rainfall totals were regressed against the seasonal irrigation hours, annual citrus production was regressed against annual irrigation hours. This was chosen because crop production is not totally dependent on rainfall, therefore when there is insufficient rainfall for citrus crops, supplementary irrigation is required to meet the daily water requirements for the citrus crop.
3.4.3 Rainfall Variability and Citrus ProductionAnnual citrus production and annual total rainfall were regressed to establish the influence of rainfall variability on irrigated citrus production. Simple linear regression analysis was used for this study because it provides the direction and strength of the relationship between the variables which are being predicted. This will determine whether variations in rainfall have an influence or not on citrus crop production.
The r-squared (r2) is an important statistic in regression. It is a statistical measure of how close the data are to the fitted regression line. The r2 statistic determine how well the regression line approximates the real data. R-squared is between 0 and 1. Zero per cent indicates that the model explains none of the variability of the response data around its mean, an r2 of 1 indicates that the regression line perfectly fits the data and that the model explains all the variability of the response data around its mean.
Citrus crop production is assumed to depend on rainfall, therefore if the regression line is equal or greater than 0,5 it means that there is a strong relationship between variations in rainfall and citrus crop production. The r2 is the proportion of the variation in citrus production which is explained by variations in rainfall. The sign of the regression equation indicates whether the variables have a negative (-) or positive (+) relationship.
The strength and direction of the relationship is shown by the coefficients. The strength of the relationship is either very strong, strong, very weak or weak and the direction is either positive or negative. The reason for using regression is to assess the influence of rainfall variability (independent variable) on citrus crop production (dependent variable). The influence of rainfall variability on irrigated citrus production will be established.
The p-value was used to determine the statistical significance of the relationship between rainfall variability and irrigated citrus production. If p-value ? 0.05, then the relationship is significant and if the p-value ? 0.05, then the relationship is insignificant.
3.5 Data PresentationData was presented in the form of tables and graphs. The Precipitation Concentration Index calculations were done using Microsoft Office Excel 2016 and the process was shown by worksheets in the form of tables. Simple linear regression against rainfall variability and citrus irrigation patterns was done using graphs. Simple linear regression analysis against annual citrus production data and annual irrigation hours, annual citrus production and annual total rainfall was also done in the form of graphs.
3.6 Chapter Summary
The chapter illustrate the methodologies that were employed to achieve the objectives and to answer the questions of the study. The study adopted quantitative enquiry approach. The objectives of this study were to establish and assess the influence of rainfall variability on citrus production. To achieve that, secondary rainfall data was collected from South African Weather Services. Citrus irrigation patterns and annual citrus production data was collected from 3 irrigated citrus farms (Farm 1, Farm 2 and Farm 3) in the Greater Tzaneen Municipality.
CHAPTER 4: RESULTS AND DISCUSSIONThis chapter presents, interprets and analyses findings on the influence of rainfall variability on irrigated citrus crop production in the Greater Tzaneen Municipality, Limpopo Province, South Africa. The aim of the research was to analyse the influence of rainfall variability on irrigated citrus production in the Greater Tzaneen Municipality. The specific objectives were to examine the rainfall variability of the Greater Tzaneen Municipality for the period 2007 to 2016, establish the influence of rainfall variability on citrus irrigation patterns and assess the influence of rainfall variability on citrus production. The Precipitation Concentration Index and simple linear regression analysis were tools employed to analyse the data. This chapter presents the outcome of the analysis as given in Chapter 3.
4.1 Seasonal Rainfall Characteristics of the Greater Tzaneen MunicipalityThe seasonal rainfall variability of the Greater Tzaneen Municipality was analysed through the Precipitation Concentration Index (PCI) from 2006-2016. Rainfall statistics of New Agatha-BOS, Westafalia and Vergelegen weather stations, for September-December (Flowering) of the previous year to January-April (Growth and Development) and May-August (Maturity and Harvesting) of the following year were considered. The PCI represents rainfall variability for each cropping season. Characteristics of each season are shown by the PCI values which are uniform, moderate, concentrated, highly concentrated or isolated. The PCI values in Tables 3, Table 4 and Table 5 indicate rainfall distribution from 2006-2016 in the seasons as recorded at the weather stations under consideration. The PCI values from the three tables show variations from highly concentrated to isolated rainfall distribution.
Table 3 shows that the rainfall for the period September-December was highly concentrated between 2006/2007 to 2015/2016. In the period January-April of the 2012/2013 season the PCI value shows that rainfall was isolated. The 2014/2015 season in the period May-August was also isolated, whereas other seasons of the periods remained highly concentrated. Isolated mean rainfall depicts high variability. The reason for the irregular seasonal rainfall distributions may be that, one month of the season received more rainfall than the other months or that one month of the season received less rainfall than the other months. According to the study by Nsubunga et al. (2014) locations with higher mean precipitation had relatively lower precipitation concentrations, while areas with lower mean precipitation had relatively higher precipitation distributions.
Table SEQ Table * ARABIC 3: Seasonal rainfall distribution (Weather Station 1: Westafalia)
Table 4 shows that September-December and January-April of the seasons 2006/2007 to 2015/2016 received moderate to high rainfall that was between 419 mm and 1353 mm. Rainfall for these periods show that the seasons were highly concentrated which depicts strong irregularity. May-August of all the seasons from 2006-2016 had the lowest total rainfall because it is the dry period and rainfall received during this time is very little. PCI values for seasons 2006/2007 and 2013/2014 from May-August were isolated. Table 4 reveals that seasons which experienced isolated distribution of rainfall is a pointer to the fact that a greater proportion of the seasonal rainfall was received during the months of the rainy season. The results agree with that of Ngongondo et al. (2011) who analysed the precipitation distribution for the season 1960 to 2007 for several locations across Malawi using the PCI. The results of the study indicated that most of the locations had high to very high concentrations of rainfall.
Table SEQ Table * ARABIC 4: Seasonal rainfall distribution (Weather Station 2: Vergelegen)
According to Table 5 the periods September-December and January-April which falls under the wet and dry-wet period received more rainfall in the seasons than the period May-August which is the dry period. The seasons 2009/2010 of the period September-December 2012/2013 and 2015/2016 of the period January-April 2013/2014 and 2014/2015 of the period May-August show that the seasons had isolated rainfall and depicts irregularity. The season 2013/2014 of the May-August period shows that rainfall was isolated with 99% irregular rainfall distribution. The other periods in the table show that the seasons had highly concentrated rainfall which depicts that the seasonal rainfall distributions had strong irregularity. Higher PCI values are an indication that rainfall is more concentrated or confined to a few rainy days during the months of the seasons. Table 3, 4 and 5 shows that the seasonal rainfall characteristics of Greater Tzaneen Municipality from 2006-2016 mostly fell within the highly concentrated precipitation category.
Evidence in this study shows that rainfall in Greater Tzaneen Municipality occurs under highly concentrated conditions. Similar studies in other parts of Africa such as Malawi, (Kumbuyo et al., 2014) and Ghana (Ndamani and Watanabe, 2014) point out that varying degrees of precipitation concentration and seasonality characterise the distribution of rainfall in Africa.
Table SEQ Table * ARABIC 5: Seasonal rainfall distribution (Weather Station 3: New Agatha-BOS)
4.2 Seasonal Rainfall Variability and Seasonal Citrus Irrigation PatternsThe relationship between rainfall variability and citrus irrigation patterns was established through simple linear regression analysis. Seasonal rainfall totals of each weather station were regressed against seasonal irrigation hours aligned to each farm for each period (Flowering, growth and maturity) based on the citrus crop calendar.
Farmers in the Greater Tzaneen Municipality irrigate citrus trees 3 times per week for 2 hours which is 40 litres (2 hours) per day, 120 litres (6 hours) per week and 480 litres (24 hours) per month. The total hours for each season is 96 hours (1920 litres) per 4 months including days of citrus crop effective rainfall (rainfall above 20 mm).
Figure 2, 3 and 4 are the results of the regression analysis which show the relationship between rainfall variability and citrus irrigation hours of each season from 2007-2016 for farms aligned with each weather station. Figure 2 Rainfall variability and citrus irrigation hours (Westafalia and Farm 2) A (September-December), B (January-April) and C (May-August), Figure 3 Rainfall variability and citrus irrigation hours (Vergelegen and Farm 3) (A (September-December), B (January-April) and C (May-August), Figure 4 Rainfall variability and citrus irrigation hours (New Agatha-BOS and Farm 1) A (September-December), B (January-April) and C (May-August).
Figure 2 shows the relationship between rainfall variability and citrus irrigation hours of Westafalia weather station and Farm 2 in the Greater Tzaneen Municipality. Figure 2 shows a negative linear relationship between rainfall variability and citrus irrigation hours for each season, citrus irrigation hours decrease with increasing rainfall totals. Figure 2 shows a significant strong negative relationship with p<0.05 and r2>0,5 in A. A significant weak negative relationship with p<0.05 and r2>0,5 is shown in B. A significant negative relationship with p<0.05 and r2>0,5 is shown in C. Further, C reveal that during the May-August season which is the dry period, rainfall received was very little (less than 120 mm) and seasonal citrus irrigation hours remained constant at 96 hours for the periods 2007/2008, 2009/2010, 2010/2011, 2011/2012, 2012/2013, 2013/2014, 2014/2015 and 2015/2016 due to insufficient rainfall (above 20 mm) for citrus crops. According to the results rainfall variability is a significant predictor of citrus irrigation hours, with the strongest relationship in A (p<0.001 and r2>0,849). Therefore, this tell us that rainfall variability influences citrus irrigation hours.
Figure SEQ Figure * ARABIC 2: Rainfall variability and irrigation hours (Westafalia and Farm 2)Figure 3 shows the relationship between rainfall variability and citrus irrigation hours of Vergelegen weather station and Farm 3 in the Greater Tzaneen Municipality. Figure 3 shows a negative linear relationship between rainfall variability and citrus irrigation hours for each season. Figure 3 shows a significant strong negative relationship with p<0.05 and r2>0,5 in A. An insignificant very weak negative relationship with p>0,05 and r2<0,5 is shown in B. An insignificant negative relationship with p>0,05 and r2<0,5 is shown in C. Further, C reveal that during the May-August season which is the dry period, rainfall received was very little (less than 110 mm) and seasonal citrus irrigation hours remained constant at 96 hours for the periods 2007/2008, 2009/2010, 2010/2011, 2011/2012, 2012/2013, 2013/2014 and 2014/2015 due to insufficient rainfall (above 20 mm) for citrus crops.
The results show that citrus irrigation hours decrease with increasing rainfall totals. However, it is shown in A that rainfall variability influences citrus irrigation hours. It is shown in B and C that rainfall variability does not influence citrus irrigation hours. Figure 3 therefore indicates that rainfall variability is a significant predictor of citrus irrigation hours during the September-December season and that rainfall variability is not a significant predictor of citrus irrigation hours during the January-April and May-August seasons.
Figure SEQ Figure * ARABIC 3: Rainfall variability and irrigation hours (Vergelegen and Farm 3)Figure 4 shows the relationship between rainfall variability and citrus irrigation hours of New Agatha-BOS weather station and Farm 3 in the Greater Tzaneen Municipality. Figure 4 shows a negative linear relationship between rainfall variability and citrus irrigation hours for each season. In Figure 4, A is a much more objective graph of Figure AA (September-December) (Refer to Appendix 1) after constraining the three major outliers distorted in 2007, 2012 and 2013. An insignificant weak negative relationship with p>0,05 and r2<0,5 is shown in A. An insignificant weak negative relationship with p>0,05 and r2<0,5 is shown in B. A significant negative relationship with p<0.05 and r2<0,5 is shown in C. Further, C reveal that during the May-August season which is the dry period, rainfall received was very little (less than 112 mm) and seasonal citrus irrigation hours remained constant at 96 hours for the periods 2007/2008, 2009/2010, 2011/2012, 2014/2015 and 2015/2016 due to insufficient rainfall (above 20 mm) for citrus crops. Also, the periods 2006/2007, 2010/2011, 2012/2013 and 2013/2014 seasonal irrigation hours remained constant at 94 hours. The results show that citrus irrigation hours decrease with increasing rainfall totals. However, A and B show that rainfall variability does not influence citrus irrigation hours whilst C show that rainfall variability influences citrus irrigation hours.
Figure 2, 3 and 4 reveals that citrus irrigation highly depends on weather conditions. When there is high rainfall amounts and sufficient rainfall for citrus crops there is no need for irrigation. Rainfall variability alone does not explain much of citrus irrigation hours. Factors such as temperature, evaporation, wind, atmospheric pressure, topography and humidity also influences citrus irrigation hours.
Figure SEQ Figure * ARABIC 4: Rainfall variability and irrigation hours (New Agatha-BOS and Farm 1)4.3 The Relationship between Citrus Irrigation Patterns and Citrus Production The relationship between citrus irrigation patterns and citrus production was assessed through simple linear regression analysis. Annual citrus production data was regressed against annual citrus irrigation hours from 2007-2016. The total annual citrus irrigation hours are 288 in the Greater Tzaneen Municipality which is 5760 litres per annum.
Figure 5 shows the results of the relationship between citrus irrigation hours and citrus production of weather stations aligned with each farm (New Agatha-BOS and Farm 1, Westafalia and Farm 2, Vergelegen and Farm 3) considered in the Greater Tzaneen Municipality from 2007-2016 using the citrus crop calendar which starts in September of the previous year and ends in August of the following year.
Figure 5 shows a negative linear relationship between annual citrus production and annual citrus irrigation hours. The results reveal that annual citrus production decreases with increasing annual citrus irrigation hours. An insignificant weak negative relationship with p>0,05 and r2 <0,5 is shown in A. An insignificant weak negative relationship with p>0,05 and r2 <0,5 is shown in B. An insignificant very weak negative relationship with p>0,05 and r2 <0,5 is shown in C. Further, C reveal that due to increasing temperatures and high rainfall variability, monthly citrus irrigation hours remained constant for some of the months during the years from 2007-2016. Figure 5 shows that citrus irrigation hours is not a predictor of citrus production which depicts that irrigation alone cannot meet the water requirements for citrus crop productivity. Unfavourable weather conditions such as high temperatures, high evaporation rates, little or no rainfall, soil moisture stress, diseases and the physical characters of the soil which citrus trees can be grown (water-holding capacity, density, texture, soil depth, structure, drainage, the similarity of the profile, erodibility, and the degree to which water can infiltrate the soil) affects citrus crop production (De Villiers and Joubert, 2006).
Figure SEQ Figure * ARABIC 5: Citrus irrigation hours and citrus production4.4 The Relationship between Rainfall Variability and Citrus Production The relationship between rainfall variability and citrus production was assessed through simple linear regression analysis. Annual citrus production data was regressed against annual rainfall totals from 2007-2016.
Figure 6 shows a positive linear relationship between rainfall variability and citrus production in the Greater Tzaneen Municipality and reveal that as citrus productivity increases rainfall variability also increases. Farm 1 shows an insignificant weak positive relationship with p>0,05 and r2 <0,5. Farm 2 shows an insignificant strong positive relationship with p>0,05 and r2 <0,5. Farm 3 shows an insignificant very weak positive relationship with p>0,05 and r2 <0,5. This is due to increasing temperatures and high rainfall variability in the areas considered between the years 2007-2016. Generally, it implies that the annual amount of rainfall in Greater Tzaneen Municipality is not stable and this reflects on the yield of citrus crops produced yearly. According to the results above rainfall variability does not affect much of citrus productivity. This suggests that other weather elements also influence citrus production.
It can be observed from Figure 6 that the annual output of citrus crops varies significantly with the annual rainfall distribution. Rainfall variability has a direct impact or influence the quantity and quality of citrus production. According to Bewket (2009) “The impact of rainfall on crop production can be related to its total seasonal or intra-seasonal distribution”. In the extreme case of El-Nino, with very low total seasonal rainfall amounts, citrus crop production could suffer. The experience of low rainfall between 2007-2016 particularly during the flowering and growing seasons, could have affected the establishment of the citrus crops. Rainfall variability from season to season greatly affects soil water availability, and thus poses citrus production risks.
Figure SEQ Figure * ARABIC 6: Rainfall variability and citrus production4.5 Chapter SummaryThis chapter presented, analysed, and discussed the findings on the influence of rainfall variability on irrigated citrus production in the Greater Tzaneen Municipality, Limpopo province, South Africa. The results of the Precipitation Concentration Index reveal that seasonal rainfall distribution in the Greater Tzaneen Municipality is highly concentrated. The study shows that citrus irrigation patterns decreases with increasing rainfall variability, the relationship between the two variables is insignificant and depends on weather conditions and the amount of rainfall received in an area. It was noted that citrus production has an insignificant weak negative relationship with irrigation patterns. The study also reveals that there is an insignificant positive linear relationship between citrus production and rainfall variability. Rainfall is a conditional process and depends on other intermediate processes like the occurrence of humidity, cloud cover and wet days.
CHAPTER 5: SUMMARY, CONCLUSIONS AND RECOMMENDATIONSThis chapter presents a summary of the research findings based on the specific objectives, conclusions from the findings and recommendations drawn from the conclusions. The study sought to analyse the influence of rainfall variability on irrigated citrus production in the Greater Tzaneen Municipality.
5.1 Summary of FindingsThe study set out to achieve the following objectives. The first objective was to examine the rainfall variability of the Greater Tzaneen Municipality (2007-2016), the second objective was to establish the influence of rainfall variability on citrus irrigation patterns and the third objective was to assess the influence of rainfall variability on citrus production.
The first objective was achieved using the Precipitation Concentration Index. The PCI reveal that seasonal rainfall variability in the Greater Tzaneen Municipality is highly concentrated and depicts strong irregularity. This leads to the conclusion that rainfall in the study area is received during a short period of time.
The second objective was achieved using simple linear regression analysis. The results of the regression show that irrigation hours decrease with increasing rainfall amounts. There is an insignificant relationship between seasonal rainfall variability and seasonal citrus irrigation hours. This leads to the conclusion that rainfall variability alone does not explain citrus irrigation hours. Irrigation hours is also affected by weather elements such as temperature, wind, atmospheric pressure, humidity, topography and rainfall received in that area. Citrus irrigation hours remain constant when there is little or no rainfall and decreases when there is sufficient rainfall for citrus productivity which is rainfall above 20 mm.
The third objective was achieved using simple linear regression analysis. The results of the regression show that annual citrus production decreases with increasing annual citrus irrigation hours. Annual citrus production and annual citrus irrigation hours have an insignificant relationship with p>0,05 and r2 <0,5. This suggests that citrus irrigation patterns alone do not influence much of citrus production. Also, the study found that there is a positive linear relationship between citrus production and rainfall variability, citrus production increases with increasing rainfall variability. However, the relationship is insignificant with p>0,05 and r2 <0,5 which suggest that rainfall variability alone does not affect much of citrus production.
5. 2 ConclusionThe main objective of the study was to analyse the influence of rainfall variability on irrigated citrus production in the Greater Tzaneen Municipality. The study found that seasonal rainfall variability in the Greater Tzaneen Municipality varied from highly concentrated to isolated over the years between 2006-2016. The study found that there is an insignificant negative relationship between seasonal citrus irrigation hours and seasonal rainfall totals depending on weather elements and topography of the area. The study reveals that citrus production decreases with increasing irrigation hours and increases with increasing rainfall variability. The study shows that there is an insignificant positive linear relationship between rainfall variability and citrus production with p>0,05 and r2 <0,5. Variability of rainfall leads to variation of citrus crop production, as rainfall is the main source of water for citrus growth.
There has been a shift on the onset and cessation of rainfall in the Greater Tzaneen Municipality. The onset alternates from November to February during the wet period and March to May during the short-wet period. The cessation alternates from June to August during the dry period and September to October during the dry-wet period. Farmers in the GTM face several challenges such as rainfall variation, limited irrigation water and high cost of farm inputs.
5.3 RecommendationsBased on the findings of this study, the following recommendations were made.
Rainfall distribution in the Greater Tzaneen Municipality do not have a definite pattern, therefore soil and water management practices should be enhanced to reduce loss of moisture from the soil and increase soil water holding capacity during the dry period to ensure that moisture stress does not suppress citrus growth and production. Trenches should be dug to reduce cases of water logging during heavy rain seasons and the water should be drained into dams and water reservoirs so that they can store water together with the existing Tzaneen dam and Letaba river should be utilised for irrigation during low rainfall seasons. Farmers should be encouraged to harvest rainwater and enhance crop diversification to caution them from rainfall variability. Farmers should practise crop intensification to increase citrus production. Farmers should not only focus on rainfall variability as the main influence of citrus crop production. They must also consider other factors such as temperature increases, wind, topography, humidity, atmospheric pressure, soil fertility, pest infestation and diseases among others. Transition to climate-smart agriculture that takes an agro-ecological approach should be encouraged. Farmers should rely less on natural rainfall, invest in long-term soil health, and use fewer external inputs, but guarantee food security. Improve the availability and quality of meteorological monitoring data, enhance climate modelling with robust articulation of uncertainties, and promote farmer awareness to the impacts of climate change through extension services.
5.4 Recommendation for Further ResearchFurther research is required on weather elements such as temperature increases, wind, topography among others which affect citrus production. Research is also required on the selection of citrus varieties that will do well with limited rainfall and on the effects of rainfall variations on the citrus market. Since irrigation and rainfall are related, research is required to find a proxy variable that will constitute both irrigation and rainfall on the influence of rainfall variability on citrus production.
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Appendix SEQ Appendix * ARABIC 1: Figure AA (September-December)Appendix SEQ Appendix * ARABIC 2: Annual Citrus Production Data
Appendix SEQ Appendix * ARABIC 3: Citrus Irrigation Patterns
Appendix SEQ Appendix * ARABIC 4: Average Rainfall Data for Three Weather Stations