An assessment of some fertilizer recommendations under different cropping systems in a humid tropical environment

摘要

Studies were carried out to determine the effects of four fertilizer recommendation systems (blanket recommendation, soil test recommendation, recommendation based on nutrient supplementation index and unfertilized control) on five cropping systems(sole cassava, maize, melon, cassava + maize and cassava + maize + melon). The experiment was a split-plot in randomised complete block design, with fertilizer recommendation systems in main plots and cropping systems in sub-plots. Observations were madeon plant growth and yield. Plant samples were also analyzed for N, P and K uptake. Cassava and melon gave higher yields in sole cropping than intercropping while maize yield under intercropping exceeded that under sole cropping by 17 percent. Cassava root yield was significantly reduced by 24 and 35 percent in cassava + maize and cassava + maize + melon plots. Fertilizer recommendation based on nutrient supplementation index (NSI) gave the highest crop yield 41, 31, and 27 t/ha of maize in sole maize,maize + cassava and maize + cassava + melon and 0.6 and 0.2 t/ha of sole melon and intercropped melon respectively. Nitrogen uptake by cassava and maize was highest under NSI, but fertilizer recommendation based on soil test gave the highest crop yield and monetary returns per unit of fertilizer used.