The Effects of Integration of Organic and Inorganic Sources of Nutrient on Maize Yield in Central Kenya

Abstract

Low soil fertility is one of the major constraints to food production in the central highlands of Kenya. Majority of the farmers use the recommendations, made more than two decades ago, which were general for central Kenya, and others meander in the maze of guessing depending on crop performance or availability of manures or fertilizers. An experiment was set up in two districts of central Kenya with the main aim of checking the effects of manure on integration with mineral N fertilizer and the N response on increasing levels of addition of 5 t ha^–1 manure. The experiment was an RCBD design, which consisted of manure as single applications and manure in combination with increasing rates of nitrogenous fertilizer application and replicated three times. The results showed that application of manure alone at 5 t ha^–1 was not sufficient to give high crop performance, although higher yields above the control were reflected, but on addition of nitrogen, higher yields were obtained even at the lowest rates of 20 kg N ha^–1. Nitrogen response curves showed that application of 5 t ha^–1 manure and N in the form of calcium ammonium nitrate up to 40 N kg ha^–1 gave yield increases but in excess of that yields decreased. This indicated that the best quantity of nitrogen to add to 5 t ha^–1 manure was 40 kg N ha^–1. Thus there is great potential in manure–nitrogen combinations.