EVALUATION OF DIFFERENT METHODS OF LIME APPLICATION AND RATES ON MAIZE PRODUCTION ON ACID SOILS OF NORTH KAKAMEGA AND UGENYA DISTRICTS, KENYA

Abstract

Western Kenya is experiencing declining food production as a result of infertile soils and soil acidity among other factors in smallholder farms. To counteract this, KARI Kakamega and Moi University have demonstrated the potential of using agricultural lime, inorganic fertilizers and Minjingu rock phosphate to address the food security problem. Despite this, the use of lime is still low due to: unawareness on lime effectiveness, and importance and mode of application by smallholder farmers. The study aimed at comparing methods of applying lime (spot, band and broadcast methods) to acid soils at 4 different rates of application (0, 2, 4 and 6 t/ha) in terms of maize performance in the two target districts of Western Kenya. On farm experiment was conducted in two sites in Ugenya district and two sites in North Kakamega district for three seasons (2010 LR, 2010 SR and 2011 LR). It was laid out in a 3x4 factorial in a randomized complete block design (RCBD) with 4 replications and a parallel experiment was laid out in RCBD with three replications for lime affordability study. Lime was applied once for three cropping seasons at planting time of 2010LR using the three methods, but with phosphorus as TSP and nitrogen as CAN applied as blankets at the rate of 26 kg/ha P and 75 kg/ha N. All the cultural practices were observed equally on all the treatments. Soil sampling was done before applying lime and fertilizers for initial site characterization and repeated thereafter to monitor changes in soil chemical properties. Analysis of the data was done using Statistical Analysis Software (SAS) version 9.1, a computer statistical package and separation of means by orthogonal contrast. Initial soil analysis suggested that the sites needed to be limed to correct soil acidity and to improve the yields. After lime was applied using the different treatments, soil pH was raised from less than 5 in all the sites to 5.85 in Ugenya district and 5.02 in North Kakamega district. The changes in pH were different with band at 6 t/ha of lime in North Kakamega district giving highest increase in pH at the end of three seasons, whereas in Ugenya district the best results were obtained from application of 6 t/ha by broadcast method. This was then reflected in availability of phosphorus for the tested crop and its yield. On average, the yields were increased from 1.50 t/ha to 3.53 t/ha and from 1.78 t/ha to 4.57 t/ha in North Kakamega and Ugenya districts, respectively. The differences between the two sites could possibly be attributed to high buffering capacity of soils in North Kakamega district due to high organic carbon and clay contents compared to those soils of Ugenya, hence lower residual effects of lime. However, economic analysis indicated that, application of 2 t/ha of lime by band or broadcast methods were economically viable in Ugenya district; while in North Kakamega district, similar quantity of lime applied by spot method or banding 4 t/ha of lime were economically viable. Thus application of large quantities of lime e.g. 6 t/ha increases the gross field benefits but reduces the net benefits due to increased cost of purchasing and transporting lime. On the minimum input experiment, it was found that a farmer can apply lime up to 0.5 t/ha in Ugenya district and still realize improved productivity, but this was not possible in North Kakamega district. Therefore there are differences in terms of lime applications depending on the sites due to soil types and climatic conditions. Thus it is recommended in this study that application of lime be done via band method in North Kakamega and broadcast in Ugenya districts.