Abstract

The effects of farmyard manure (FYM) and triple superphosphate (TSP) as sources of phosphorus, when applied with or without lime, on selected soil chemical properties, and the initial and residual maize yields, were compared for two consecutive seasons at two acidic, phosphorus-deficient sites, Khwisero and Maseno, in western Kenya. Nutrient inputs, consisting of two sources of phosphorus: TSP and FYM, applied as sole or in combination at two rates of 30 and 60 kg P ha-1, and lime were applied in the first season only. All treatments with lime maintained the soil pH above 5.5 and reduced exchangeable acidity for the two seasons. Application of FYM also raised the soil pH, but this did not exceed 5.5, and also significantly reduced exchangeable acidity, especially at Khwisero. Sole application of TSP failed to significantly increase maize yields above the control with no nutrient inputs likely due to aluminium toxicity. Sole application of FYM, however, significantly increased maize yields above the control with no nutrient inputs due to the nutrients it contained and its ability to reduce Al toxicity. When TSP was combined with lime or FYM, the deleterious effects of soil acidity were ameliorated and maize responded to the applied TSP. Application of FYM to provide 60 kg P ha-1 together with lime gave the highest maize grain yields at both sites in both seasons. FYM treatments had the highest residual maize yields but inorganic fertilizers did not show significant residual effects. Combining lime with FYM at 60 kg P ha-1 is a promising strategy to manage acidity and P deficiency at these sites.

Key words: Farmyard manure, lime, phosphorus, soil acidity, residual effects, western Kenya.