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A study was carried out to investigate the influence of agricultural lime (21% CaO) from Koru, Kisumu on soil properties and wheat yield on acidic soils of Uasin Gishu county. Field trials were conducted at Chepkoilel University College farm and in Kipsangui area of Uasin Gishu county. Soils were analyzed to determine their pH, available P and other nutrient levels before treatment application. The experiment was a split plot arrangement with two wheat varieties as the main plots and the lime treatments as the subplots. The two varieties compared were ‘Njoro BW 2’ and ‘KS Mwamba’ characterized as tolerant and moderate tolerant to soil acidity, respectively. Phosphorus and nitrogen were applied as a blanket treatment at the rates of 40 kg P205 /ha and 46 kg N/ha respectively. Lime was applied at the rates of 0.0, 0.5, 1.0, 1.5 and 2.0 t/ha. Soils from the two sites were acidic with low to moderate available P for Chepkoilel and Kipsangui sites respectively. Soil pH and soil available P increased with the increase in the rate of lime addition. Wheat grain yield increased significantly (p=0.05) due to soil acidity amendment above the control. There was a high positive correlation between wheat yields and soil available P at both sites at harvest. High cost of inorganic inputs, low wheat grain prices and the effects of the erratic rains made the majority of the treatments economically unviable for adaptation by farmers. However, the most profitable treatment was 2 t/ha of lime in Njoro BW 2 at Kipsangui site. There was no viable treatment at Chepkoilel site. Higher wheat yields may probably be achieved from rates of lime above 2 t/ha. more...

SummaryThe manure that is returned to croplands each year is an important resource in the subsistence farming systems of eastern Kenya. Measurements on several farms have shown that the manure being used is of very poor quality. Analyses of soil samples from beneath the bomas (small enclosures) where animals are kept indicate that substantial losses of nutrients occur through leaching; ammonia volatilization and denitrification may also be involved. Current practice is to apply the manure at rates that appear to make poor use of this scarce resource. The findings are discussed in terms of what changes to the system may be feasible to reduce losses of nutrients, and to improve the quality of the manure and the effectiveness of its use. more...

There is much current interest in the potential role of agroforestry in the mitigation of nutrient depletion in Sub-Saharan Africa. Using data from farm surveys and trials, a static model of N and P flows was constructed for a standard farm system, representative of typical subsistence farms in humid parts of the East African Highlands. The model was used to explore the possible impact of improved agroforestry systems on nutrient budgets, to identify priorities for research. Soil nutrient balances in the standard farm system were - 107 kg N and - 8 kg P ha−1 yr−1. Agroforestry systems did not significantly reduce the N deficits except when a high proportion of the total biomass was returned to the soil, rather than removed from the farm. Agroforestry increased N input through biological N fixation and deep N uptake, but this was offset by a larger nutrient removal from the farm in harvested products, which increased from 38 kg N in the standard system to 169 kg N ha−1 yr−1 in an intensive dairy-agroforestry system. Agroforestry did not increase P inputs, and harvested P increased from 6 kg P in the standard farm system to 29 kg P ha−1 yr−1 in the dairy-agroforestry system. Thus, moderate P inputs, of 20 kg P ha−1 yr−1 were required to maintain soil P stocks. N leaching from the field was the most significant nutrient loss from the farm system, with a range of 68 to 139 kg N ha−1 yr−1. The capture of subsoil N by deep-rooted trees in agroforestry systems substantially increased N-use efficiency, providing 60 kg N ha−1 yr−1 in the dairy-agroforestry system. The budgets were sensitive to N mineralization rates in subsoils, N losses from soils and manures, and effectiveness of deep-rooted plants in subsoil N capture, for which there is little data from the region. Therefore, high priority should be given to research in these areas. The current model can not account for important feedback mechanisms that would allow analysis of the long-term effects of nutrient budgets on nutrient availability and plant productivity. Dynamic models of farm nutrient budgets that include such interactions are needed to further assess the sustainability of farming systems. more...

SummaryMaize (Zea mays L.) and common bean (Phaseolus vulgaris L.) were each sown at four plant densities, including zero, in a bivariate factorial design at Kiboko Rangeland Research Station, Kenya during the long and short rains of 1990. The design gave nine intercrops with different proportions of maize and beans, and six sole crops, three of maize and three of beans. Seed yields in both the sole crops were not significantly affected by plant density, so the mean yield was used to calculate the Land Equivalent Ratio (LER), which averaged 1·09 in the long rains but only 0·87 in the short rains. These low values were apparently due to the fact that beans failed to nodulate and fix nitrogen in the study area. The difference in LER between seasons was probably caused by differences in the amount and distribution of rain in relation to crop growth. Maize was more competitive than bean, each maize plant being equivalent to between 0·7 and 3·4 bean plants depending upon the treatment and the season. more...

Vertisols are heavy clay soils with 30 to over 70% clay dominated by smectite mineralogy. They are the most widely distributed soils worldwide located mainly in tropical and sub-tropical regions. In Africa, they occupy about 3.5% or 99 million hectares of the landmass located mainly in eastern Africa. In Kenya, they occupy about 5% or 2.8 million hectares of the landmass and occur mainly in arid and semi-arid areas (ASALs). They are potentially very productive soils because of their high cation exchange capacity and water retention, moderate soil fertility and low salinity/alkalinity problem. However, their poor infiltration and internal drainage result in severe management problems. Traditionally, the Vertisols in Kenya were and still are used largely for extensive livestock grazing, however, due to increased population pressure and emigration of people from humid high potential areas to the ASALs; they are being converted to arable cropping. Vertisols cropping in Kenya is, however, a new utility system being embraced enthusiastically in spite of the serious management constraints observed. The major constraints include water logging and tillage difficulties, which pose serious challenges to their utilization for cropping in the country. In this chapter, problems and challenges associated with the ecosystem, population pressure and traditional and current land use including livestock grazing and arable cropping in the Vertisols are considered in relation to sustainable land use and management. In conclusion, views on the way forward towards sustainable land use and management of the Vertisols including proposals on stocking rates and cropping systems for maintaining the soil fertility and productivity while minimizing soil erosion and land degradation are given. Use of the drainage landforms (DLs) increased maize and sunflower grain yields by 5–57% and above-ground total biomass significantly. more...

(1990). Effect of Form and Method of Phosphate Fertilizer Application on Maize, Sorghum and Millet Growth in a Semi-Arid Environment of Kenya. East African Agricultural and Forestry Journal: Vol. 55, No. 4, pp. 239-246. more...

Most cropland soils in East Africa and the tropics are in general highly weathered, leached and deficient in plant nutrients particularly nitrogen and phosphorus. Over the past 80 years or so, effo... more...

(African Crop Science Journal 1999 7(4): 549-558)

Effects of mono-, diammonium, and superphosphate with added urea or ammonium nitrate on corn (Zea mays L.) growth were studied in the field in 1971 and 1972. At the rate of 100 kg P2O5/ha, none of the carriers affected emergence of seedlings in five Quebec soils. Leaf P content at silking time was of little benefit in predicting P status of the plants, or in differentiating among the carriers. Phosphorous applications gave significant corn yield increases, with carriers performing alike when averaged over all sites. However, some yield differences among carriers occurred on some soil types and seasons. These carrier differences were not consistent and remain to be clarified. The ammonium phosphates compared with the check generally hastened maturity but reduced potassium levels in leaf tissue of corn. more...