In Situ Soil Moisture Conservation: Utilization and Management of Rainwater for Crop Production

The salient results of in situ soil water conservation technologies that have been extensively tested and found suitable for increasing soil moisture for increased land productivity in the arid and semi-arid lands (ASALs) of eastern Kenya are reviewed in this paper. The technologies reviewed are fanya juu terraces, contour bunds, negarims, trapezoidal bunds, on-farm micro-catchments, Zai pits, tumbukiza, tied ridges, deep tillage and sub-soiling and ripping. These technologies hold rainwater on the soil surface thereby allowing it more infiltration time leading to enhanced soil moisture status, which would not be attained in the absence of these interventions. Zai pits, tumbukiza and deep tillage when used together with soil fertility improvement can increase crop yields by 4-10 times when compared to other similar fields cultivated conventionally. When tied-ridging tillage is used together with fertilizer, manure or their combination it can increase crop yields by 100-300 %. Sub-soiling and ripping increases crop yields by 50-100 % when used together with soil fertility improvement. Micro-catchment technology at 1: 1 and 2: 1 catchment to cultivated land ratio can increase crop yields, but is not practised due to land limitation. Use of fertilizers and or manures with in situ soil moisture conservation leads to improved water use efficiency by crops planted in the semi-arid eastern Kenya. It is, therefore, proposed that in situ rainwater conservation technologies should be an integral part of the farming systems for increased soil moisture conservation, crop production and food security in the semi-arid Eastern Kenya.