INFLUENCE OF AGRICULTURAL LIME ON SOIL PROPERTIES AND WHEAT (Triticum aestivum L.) YIELD ON ACIDIC SOILS OF UASIN GISHU COUNTY, KENYA

Abstract

Soil acidity, one of the contributors to soil fertility depletion, has become a matter of concern in sub- Saharan Africa. In Kenya, 13% of the soils are acidic and are considered to be low fertility due to highly weathered and leached nature. A study was carried out to investigate the effect of agricultural lime from Koru, Kisumu (21% CaO) 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 district. Soils were analysed to determine their pH, available P, nitrogen and organic carbon before treatment application. The experiment was arranged in a splitplot arrangement with two wheat varieties as the main plots and the lime treatments as the subplot. The two varieties were Njoro BW 2, which is tolerant to soil acidity and KS Mwamba which is moderately tolerant to soil acidity, were compared. Phosphorus and nitrogen were applied as blankets 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 (pH4.9) and Kipsangui (pH5.3) respectively. Wheat was planted at the rate of 125 kg/ha. Both sites have sandy loam soils. There was a significant effect (P<0.05) on the growth pattern of wheat crop as influenced by agricultural lime above the control in both wheat varieties and sites. However, Kipsangui site had significantly (P<0.05) higher growth rate than Chepkoilel because of the fair rainfall distribution and amounts it received during the year. Wheat grain yield increased significantly (P<0.05) at sites due to soil acidity amendment (CaO), P and N addition above the control. Kipsangui site had higher grain yield compared to Chepkoilel site because again of the high and fair distribution of rainfall during the year. The soil nutrient levels of P and N were also highly significantly (P<0.05) at Kipsangui. At Kipsangui the average yield were 1.87 t/ha and 1.43 t/ha for Njoro BW 2 and KS Mwamba varieties respectively while at Chepkoilel site the wheat grain yield was 1.55 t/ha for Njoro BW 2 and 1.23 t/ha for Mwamba. The highest yield of straw of 2.18 t/ha and 1.89 t/ha of Njoro BW 2 was achieved with lime addition of 2 t/ha in Kipsangui and Chepkoilel, respectively, while KS Mwamba wheat variety also gave the highest straw yield of 1.17 t/ha at Chepkoilel and 1.27 t/ha at Kipsangui with the highest lime addition at 2 t/ha. There was a high positive correlation between wheat yields and soil available P at Kipsangui and Chepkoilel after 125 days (at harvesting). Lime increased P and N uptake in both wheat grain and straw. However, results from this study suggest probably higher rates of lime would have to be applied to achieve favourable soil pH and higher soil available P for long periods of time. From the experimental sites, it is recommended that fertilizer in combination with lime be adopted. The influence of lime on soil water retention should be monitored for a long time to get conclusive results on moisture retention in soils. High cost of inorganic inputs, low wheat grain prices and the effects of the rains made the majority of the treatments economically unviable for adaptation by farmers. However, the most profitable treatment was lime addition at 2 t/ha in Njoro BW 2 at Kipsangui site. Higher wheat yields may probably achieved from rates of lime above 2 t/ha.