EFFECTIVENESS OF LIMING MATERIALS AND PHOSPHORUS FERTILIZER APPLICATION ON MAIZE PRODUCTION IN ACID SOILS OF SIAYA AND KAKAMEGA COUNTIES.

Abstract

Soil acidity is a major contributor to soil infertility in western Kenya. Smallholder farmers in this region have persistently realized low yields (< 1 t ha-1 season-1 maize) in comparison to potential estimates of 6 – 8 t ha -1season-1. Liming, as an intervention to ameliorate soil acidity, is hardly practiced in the region where acid soils occupy about 0.9 million hectares of farm land. An on-farm research was conducted during the 2010 long and short rains and 2011 long rains at selected sites in Kakamega (Chimoroni and Tumbeni) and Siaya (Got Nanga and Sihay) Counties, to evaluate direct and residual effects of various lime sources on soil pH, phosphorus availability and maize yields. Two separate experiments were carried out. In one, two agricultural lime materials from two sources; Koru, (20.8 % CaO) and Athi River (45 % CaO), were used to evaluate maize yield response, soil pH and P availability to a combination of lime and P fertilizer. The experiment was laid out in a split plot design with 3 replicates. The second experiment tested the effectiveness of four liming and P fertilizer sources (Koru and Athi River lime, Minjingu phosphate rock - MPR (38 % CaO, 29 % P2O5) and Mavuno fertilizer (26 % P2O5, 10 % N, 10 % CaO, 4 % MgO, 4 % S2O) on soil pH, P availability in soil and maize yields. Triple superphosphate (46 % P2O5), supplied P to the two agricultural limes without P. The experiment too was laid in a split plot design. A blanket application of 75 kg N ha-1was applied to all plots with exception of the absolute control. Comparison between treatment means was achieved by using single degree of freedom contrasts. Results for 2010 LR indicated significant (p<0.05) responses of maize yield to the soil amendment materials applied. Koru lime applied at 3 t ha-1 gave the highest yield of 4.96 t ha-1 (Got Nanga site) and 3 t ha-1 Koru lime + TSP gave a yield of 3.85 t ha-1in Chimoroni site for the first experiment. For the second experiment, Mavuno fertilizer (0.48 t ha-1) had the highest yield of 6.72, 5.70 and 4.72 t ha -1 at Sihay, Got Nanga and Tumbeni sites, respectively. There was a positive and significant correlation between yield and extractable soil P in all the sites at the third sampling. During 2010 SR, maize yields were very low, due to the poor and inadequate rainfall experienced during that season. In the final season (2011 LR), the soil amendment materials still showed residual effects, though there was a reduction in maize grain yield, soil pH and extractable soil P values in almost all the sites. Mavuno fertilizer (0.24 t ha-1) gave the highest external P use efficiency of 182.9 kg grain kg-1 of applied P at Sihay. In conclusion, lime application increases yield above the control, though, the yield is insignificant except at Got Nanga where 3 t ha-1 lime significantly increased maize yield. Lime in combination with P is the best practice for optimum yield. Additionally, fertilizer blends (Mavuno) can both lime the soil and provide essential nutrients as was observed in this experiment. Lime requirements and nutritional levels of these soils should be determined and farmers advised accordingly for better maize production in this region. A green house study for the second experiment was conducted to isolate effects of materials used in the field after it was realized that Mavuno performed better. Soil was collected from Sihay and Tumbeni. All treatments without K, Mg, S, and Zn received these nutrients in forms of solutions except K and S. The treatments were arranged in a complete randomize design. Dry matter yield of the control treatment differed significantly (p < 0.05) from treatments. However, treatments did not differ significantly from each other in Sihay and Tumbeni soils. Thus, Mavuno fertilizer performed better in the field due to both macro and micronutrients it contains