PROF. KARUKU GEORGE NJOMO

Influence of soil type, vegetation, landuse and environmental problems on infiltration rate into the two soils on the semi-arid Sibilo/Loruk watersheds (water catchment) in Baringo District was investigated. Infiltration was assessed during the dry and wet seasons by a double cylinder, infil¬trometer. Infiltration rates significantly dif¬fered among soils and site conditions (treatment) in both areas after 10 minutes and 180 minutes. Among site conditions in both seasons, intake rates were highest under Tree/Bush (TB), followed by culti¬ vated soils, intermediate on Open Grass (OG) and lowest on Bare Ground (BG). Cultivation temporarily increased infiltra¬tion rates. Bulk density (Pb), saturated hydraulic conductivity (Ksat) and organic carbon (Oe) sign.ificantly influenced infil¬tration in both areas during the dry and wet seasons in 1991/92. It was observed that water soil-erosion rates was higher in Loruk than Sibilo and this could be the rea¬son for high siltation of Lake Baringo and significant drop in the recorded fish output in the lake. This has not only resulted in less nutritional food for the people of the district but has meant loss of re~enue to the local fishermen. The siltation creates envi¬ronmental problems in the lake for produc¬tion of fish for child survival and develop-. ment in future. Fish is another cheap source of protein which could be more fully exploited. In Baringo area, water and sanitation are a big problem. The Baringo community in particular, has identified the need for water as its top priority. Water and sanitation is an important component for child survival and development in both areas

This study uses CROPWAT model to predict water use in rainfed agriculture and simulate irrigation requirement for tomato production in Kabete Field Station. The model predicted increased irrigation requirement for tomato crop of 33.1, 28.1 and 36.6 mm water, in the 1st, 2nd and 3rd 10-day periods of development stage, respectively. The crop evapotranspiration (ETc) requirements by tomato crop were predicted at 456.5 mm for the short rainy season while actual evapotranspiration (ETa) was 232.1 mm for the short rains giving a yield response factor of 0.49. The model suggested an addition of 253.7 mm of irrigation water in order to realize optimal tomato yields as the crop experienced an irrigation deficiency of 48.8%. The moisture deficit at harvest was 63.6 mm of water which resulted in total yield reduction of 51.3%. In relation to actual yields calculated, the mean potential optimal tomato yields in the study area were 23.3 Mg/ha with proper soil management and adequate water supply. The suggested supply system was at 10 days irrigation interval/stage where the soils were irrigated just below or above field capacity. Rainfall losses and irrigation requirements would be reduced to 41.9 and 267.7 mm, with minimum water deficit at harvest of 15.5 mm and an irrigation efficiency of 100%. At this point, ETa would equal ETm and optimal tomato yield would be obtained with yield losses predicted at 0.1%. Yield gap analysis revealed that radiation, sunshine and temperature are favourable for crop production, but the heavy dependence on rainfall makes the area very vulnerable to drought.

This study uses CROPWAT model to predict water use in rainfed agriculture and simulate irrigation requirement for tomato production in Kabete Field Station. The model predicted increased irrigation requirement for tomato crop of 33.1, 28.1 and 36.6 mm water, in the 1st, 2nd and 3rd 10-day periods of development stage, respectively. The crop evapotranspiration (ETc) requirements by tomato crop were predicted at 456.5 mm for the short rainy season while actual evapotranspiration (ETa) was 232.1 mm for the short rains giving a yield response factor of 0.49. The model suggested an addition of 253.7 mm of irrigation water in order to realize optimal tomato yields as the crop experienced an irrigation deficiency of 48.8%. The moisture deficit at harvest was 63.6 mm of water which resulted in total yield reduction of 51.3%. In relation to actual yields calculated, the mean potential optimal tomato yields in the study area were 23.3 Mg/ha with proper soil management and adequate water supply. The suggested supply system was at 10 days irrigation interval/stage where the soils were irrigated just below or above field capacity. Rainfall losses and irrigation requirements would be reduced to 41.9 and 267.7 mm, with minimum water deficit at harvest of 15.5 mm and an irrigation efficiency of 100%. At this point, ETa would equal ETm and optimal tomato yield would be obtained with yield losses predicted at 0.1%. Yield gap analysis revealed that radiation, sunshine and temperature are favourable for crop production, but the heavy dependence on rainfall makes the area very vulnerable to drought.