Effects of Manure, Lime and Mineral P Fertilizer on Soybean Yields and Soil Fertility in a Humic Nitisol in the Central Highlands of Kenya

Abstract

Soybean ( Glycine max (L.) Merrill) is one of the most important legume crops being introduced into the smallholder farming systems of the Central Highlands of Kenya (CHK) to improve income and household nutrition of farmers. However, phosphorus fixation, depletion of soil nutrients and soil acidity are major causes of low yields. The objective of this study is to evaluate effects of manure application, liming and phosphorus application on soil properties and soybean performance. The study consisted of 8 treatments: manure (0, 5 and 10 t ha -1 ), lime (0 and 2 tha -1 ) and P fertilizer (0, 30 and 60 kg P ha -1 ). The experiment was laid out in a randomized complete block design (RCBD) with 4 replicates in plots of 4 m × 4.5 m. Manure and lime significantly reduced exchangeable acidity and increased soil pH. Application of manure alone or combined with lime or P fertilizer also increased Mg and K. Treatments that had sole lime, lime combined with manure and manure combined with P applied gave a significant increase in exchangeable Ca. Soybean responded well and significantly to application of manure either alone or combined with lime, P or both. These results showed the potential role of lime, manure and P fertilizer in improving soil fertility and soybean yields.