Analysis of a Long-Term Maize Yield Field Trial Data to Determine the Effect Of Continuous Application of Fertilizers

Abstract

The Kenyan population pressure in the high and medium potential areas has led to continuous cropping thus resulting to severe soil degradation. This has led to the use of integrated nutrient management strategies in order to reduce nutrient depletion by use of low cost inputs under sustainable land management. This study seeks to find the effect of farmyard manure, organic fertilizers (NP) and residues on maize yields. This long term trial was started in 1976 and is still going on. Data was analysed up to 2001. The broad objective of this study is to determine the effect of continuous maize cropping with, manure addition, maize stover incorporation and nitrogen-phosphorus fertilization on maize crop yields. The design used is Randomised Complete Block Design (RCBD) with 4 replications. Analysis was carried out to determine which treatments are superior over a long period of time and models fitted to establish the optimal levels of farm yard manure and organic fertilizer application. In chapter three it is shown that applying organic fertilizers together with farm yard manure is beneficial (p=O.OOO)to the maize crop. Residues alone have no significant benefits to the crop (p=O.240). The study has establislied that the optimal application level for farm yard manure is about ]3 t/ha and that for organic fertilizer is 220kg/ha.