WHEAT RESPONSE TO PHOSPHORUS FERTILIZERS AND AGRICULTURAL LIME IN UASIN GISHU COUNTY, KENYA.

Abstract

When water is not limiting, soil acidity, deficiencies of phosphorus (P) and nitrogen (N) amongst others are considered to be the major causes of low wheat yields in Uasin-Gishu County, Kenya. In this County, average annual wheat grain yields have always been low with an average of 2.34 t ha-1 but small scale farmers get much lower yields of as low as 0.7 t ha-1. The study aimed at investigating response of wheat growth pattern, grain and straw yields, and soil chemical properties as influenced by liming at 2 t ha-1 (main plots), P sources 23:23:0 (NPK), (DAP) 18:46:0, and 0:20:0 (SSP) - (sub-plots) and, P rates (sub sub-plots) P0; 0 kg P ha-1, P1; 8.8 kg P ha-1, P2; 17.6 kg P ha-1 and P3; 26.4 kg P ha-1. A split-split plot arrangement laid out in a RCBD experiment was set up in two sites; Chepkoilel and Kipsangui in 4 m2 plots, replicated 3 times. Data collected on soil (pH, available P, SOC, and exchangeable K, Ca, Mg, Na), plant height, grain, straw yields and plant total P and N were subjected to ANOVA using SAS 9.1 for Windows 2012 statistical package. Lime application increased the soil pH thus likely making P more available in the acidic soils in the two sites and generally increased exchangeable cations K, Mg, Na and Ca thus improving soil fertility. Phosphorus rich fertilizer application resulted in a significant (p≤0.05) increase in P and soil nutrients content during plant growth, heading and maturity stages. ANOVA showed lime application had a significant (p≤0.05) rise in the wheat grain yield in both sites. Fertilizer application and liming significantly (p≤0.001) improved grain yield in both sites. Rates of applied P also significantly (p≤0.001) influenced wheat grain yields in the two sites. Use of compound fertilizers with balanced ratios of nutrients resulted into increased wheat grain yields. Phosphorus application plus lime at 2 t ha-1 had a significant (p≤0.001) influence on the straw yield in Chepkoilel and Kipsangui. Lime at 2 t ha-1 significantly (p≤0.05) influenced straw yields in Kipsangui and Chepkoilel sites. NPK (23:23:0) fertilizer recorded higher wheat straw means in Kipsangui and Chepkoilel, with DAP giving the lowest yields. Grains’ total N in Kipsangui was higher under SSP (1.80 %). There was no significant difference (p≤0.05) in the level of total N in grain using DAP and 23:23:0 in Kipsangui and Chepkoilel respectively. P uptake was high under P3 application rate plus liming. P uptake was high in both sites. The study recommends 23:23:0 fertilizers at a rate of 26.4 kg P ha-1 for Chepkoilel and Kipsangui plus lime at 2 t ha-1 as most productive and economical. The study also recommends further research on fertilizer use to further increase wheat grain yields from 5.39 t ha-1 to the optimum of 7.2 t ha-1, as the study only managed a 43.0 % wheat grain increase.