Sub-soiling to break hardpan, followed by ripping to widen furrows is an effective water harvesting technique

1. Integrated soil fertility and water management farmers field school A KARI scientist stressing the importance of legumes in crop rotations Integrated soil fertility and water management methods for increased crop production in the drylands of Kenya Sub-soiling to break hardpan, followed by ripping to widen furrows is an effective water harvesting technique E.M. Gichangi, P. Kathuli, S.N. Nguluu and J.M. Wambua, KARI-Katumani, P.O. Box 340-90100 Machakos, Kenya Sub-soiling and ripping Characteristics of the semi-arid areas of Kenya Rainfall • low in amount (500-800 mm per annum) and • unpredictable in terms of onset and distribution Soils • Low in fertility and organic matter • shallow depth and susceptible to surface crusting and compaction Water harvesting and integrated nutrient management is an important strategy for increasing crop production while simultaneously conserving the environment. Integration of crop and livestock management, use of household waste, composting and incorporating crop residues into soil are ways to improve nutrient cycling Soil fertility improvement options • Application of animal manure provides a means of recycling nutrients but is usually available in insufficient quantities and of poor quality • Application of small quantities of inorganic fertilisers in combination with manure is recommended to increase nutrient levels • Inclusion of legumes in rotations to fix atmospheric nitrogen and adds external nitrogen to the crop-soil ecosystem Objectives • to increase the efficiency of rain water utilisation • to add nutrients to replenish stocks and flows in soil • to block nutrient flows leaving the farm (‘leaks in the system’ e.g. through soil erosion, leaching etc) • to Increase the efficiency with which nutrients are used by the various production systems Improved water management options Covering manure with dry grass minimises nitrogen losses A healthy Katumani maize crop treated with cow manure/inorganic fertiliser Tied-ridging • Tied-ridging offers good potential for water conservation • Tying the furrows allows in-situ water harvesting with increased water infiltration into soil and reduced runoff copyediting and layout design by John Ayemba photographs by John Abok