An Integrated Approach to the Delineation of Arable
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AN INTEGRATED APPROACH FOR THE DELINEATION OF ARABLE LAND AND ITS CROPPING SUITABILITY UNDER VARIABLE SOIL AND CLIMATIC CONDITIONS IN THE NKONKOBE MUNICIPALITY, EASTERN CAPE, SOUTH AFRICA ALEN MANYEVERE BSc. Agric. (Soil Science); MSc. Agric. (Soil Science) A thesis submitted to the Faculty of Science and Agriculture in fulfillment of the requirements for the Doctor of Philosophy in Soil Science Department of Agronomy University of Fort Hare Alice, South Africa Promoters: Prof P Muchaonyerwa Prof PNS Mnkeni Prof MC Laker 2014 DECLARATION I, ALEN MANYEVERE, declare that this thesis is my own work and that views from other authors have been cited. Signature Date Place: Alice, South Africa ABSTRACT Arable crop production in Nkonkobe Municipality is low due to abandonment of potentially productive land and low productivity of the cultivated land. Little attention has been given to farmers‟ perspectives with regards to crop production and land abandonment. Understanding the relationships of indigenous knowledge systems, where local approaches to soil classification, appraisal, use and management and land evaluation, and scientific approaches could be important for the effective use of available soil resources while avoiding those resources that are vulnerable to degradation. In addition, the interactions between soil factors and climate could be useful in understanding the erodibility of soils. The intergration of scientific research and indigenous knowledge systems could help in the identification and delineation of high potential land and on crop suitability evaluation. The objectives of the study were: (i) to determine farmers‟ perspectives with regards to land utilisation and abandonment, constraints on crop production and crop preferences, (ii) to integrate and compare indigenous knowledge systems with scientific approaches of soil classification and potential, (iii) to determine the effect of climate and soil factors on erodibilities of soils in the Municipality (iv) to delineate arable land and evaluate its suitability for maize, potato, sorghum and cowpea under rainfed agriculture. Using semi-structured and open-ended interviews, information on limitations to crop production, cropping preferences, indigenous soil classifications, cropping potential ratings and erosion was captured. Descriptive and correlation statistics were used to analyse farmers‟ responses. The information was later used for a pilot participatory mapping and the determination of the agricultural potential of the soils in three selected villages of the Municipality. Field boundaries of soil texture, colour, depth, and slope position were captured using global positioning systems (GPS). The relationship between the degree of erosion and soil and slope factors was analysed by step-wise regression. Crop suitability for rainfed agriculture was done using the FAO guidelines for Land evaluation for rainfed agriculture. The spatially referenced crop suitability classes were produced by applying the Law of Limiting Combinationusing GIS Boolean Logic. The major biophysical factors, affecting crop production and land utilisation were soil degradation and low and erratic rainfall, while other factors included lack of farming equipment and security concerns. Maize, spinach and cabbage were the main crops grown, with maize, ii sorghum and wheat the most abandoned crops. While it was difficult to accurately correlate indigenous classification with international scientific classification, the importance of colour, texture and soil depth for both classification and soil potential, suggests that some form of correlation is possible which enabled communication and other extension information to be conveyed. The shallow and stony soil (urhete) correlated well with the Leptosols in World Reference Base (WRB) or Mispah and shallow Glenrosa soils in the South African system. The red structured clays (umhlaba obomvu) matched the Nitisols in WRB or Shortlands in the South African system. The non-swelling black clayey soils (umhlaba omnyama) matched soils with melanic A horizons in both the WRB and South African soil classification systems. The dongwe and santi soils developed in alluvial sediments belonged to the Dundee, Oakleaf or Augrabies soils in the South African classification system and fluvisols or Cambisols in the WRB system. There was good agreement between farmers‟ assessment of the cropping potential and scientific approaches but scientifically high potential red soils were rated lowly by the farmers due to difficulties in management caused by shortages of farm machinery, especially under dryland farming. Overall, the soil factors affecting erosion were influenced largely by climate, while parent material was also important. Climate had a dominant influence on soil factors most notably fine sand and very fine sand fractions and exchangeable sodium percentage being more important on soil forms occurring in arid and semi-arid climate and less in the sub-humid and humid areas, where clay mineralogy, particularly kaolinite and sesquioxide dominated. Dolerite derived soils were the most stable and should be given the highest priority for cropping development while mudstone and shale derived soils had a lower cropping potential. While slope gradient and length had some effect on soil erosion in arid and semi arid environments its influence was generally overshadowed by soil factors especially in humid zones. Cow pea and sorghum were the most adapted crops in the region while potato and maize were marginally suitable under rainfed agriculture. The study revealed that most adapted crops were not necessarily the most preferred crops by the farmers. A small percentage of the land was delineated as arable and therefore optimisation of this available land should be prioritized. iii ACKNOWLEDGEMENTS Firstly, I thank God for giving me the wisdom and good health to undertake this study. I would like to thank the Govan Mbeki Research and Development Centre (GMRDC) and National Research Foundation (NRF) for providing funds towards my upkeep, fieldwork and laboratory activities. Special thanks go to my promoters, Professors P.Muchaonyerwa, P.N.S Mnkeni and M.C Laker, for their guidance and support throughout the study. To fellow postgraduate colleagues in the Department of Agronomy, I say thank you for the moral and logistical support you gave me during the course of the study. I would like to thank my wife, Rosemary and children, Kudzaishe and Makanaka for their support and understanding during the busy times when I could not accord them time and love because of my study commitments. iv CONTENTS OF CONTENTS CONTENTS PAGE DECLARATION ........................................................................................................................ i ABSTRACT ............................................................................................................................... ii ACKNOWLEDGEMENTS ...................................................................................................... iv CONTENTS OF CONTENTS ................................................................................................... v CHAPTER 1 .............................................................................................................................. 1 GENERAL INTRODUCTION .................................................................................................. 1 1.1 Introduction .......................................................................................................................... 1 1.2 Research problem................................................................................................................. 4 1.3 Objectives ............................................................................................................................ 5 CHAPTER 2 .............................................................................................................................. 6 2.0 Literature Review................................................................................................................. 6 2.1 The role of agriculture in food security ............................................................................... 6 2.2 Brief history of agricultural land and its use in the Nkonkobe Municipality ...................... 7 2.3 Land use and degradation .................................................................................................... 9 2.4 Local soil classification and agricultural potential based on indigenous knowledge ........ 10 2.6 Delineation of arable land and land suitabilityevaluation .................................................. 17 2.7 Multicriteria Analysis in land suitability studies ............................................................... 21 CHAPTER 3 ............................................................................................................................ 25 FARMERS‟ PERSPECTIVES WITH REGARD TO ARABLE CROP PRODUCTION: AN ANALYSIS OF NKONKOBE MUNICIPALITY, SOUTH AFRICA ................................... 25 3.1 Introduction ........................................................................................................................ 25 3.2. Materials and methods ...................................................................................................... 27 3.2.1 Study area........................................................................................................................ 27 v 3.2.2 Farmer interviews ..........................................................................................................