Agronomic Effectiveneness of Poor Quality Manure Supplemented with Phosphate Fertiliser on Maize and Groundnut in a Maize-Groundnut Rotation

A survey of groundnut and maize fields in the smallholder farms showed that soils sampled from maize fields had significantly (P<0.05) higher pH, calcium and phosphorus than those from groundnut fields. It was established that there was limited use of mineral and organic fertilisers to groundnut, and this could be linked to limited resources and the risk associated with fertilisation in an environment of low and uncertain rainfall. The low fertility of groundnut soils has contributed to the decline in groundnut yields. The agronomic effectiveness of cattle manure supplemented with phosphate fertiliser, on maize and groundnut, was evaluated in factorial experiments on five smallholder farms in Zimbabwe. Increased groundnut and maize yields were obtained where manure had been applied at rates up to 20 t ha-1 at the majority of the sites. The benefit of supplementing manure with phosphate fertiliser was not evident. Factorial analysis indicated significant main effects of manure (P<0.01), for both direct and residual effects. The main effect of phosphate was not significant at all but one site, while no manure x phosphate interactions were observed. Regression analysis indicated linear effects of manure on maize yield and groundnut pod yield. The different qualities of manure used at the different sites (based on total manure N content) may have contributed to the variations in response observed at the different sites. Basic economic analysis revealed that it was more profitable to use direct and residual manure fertility on groundnut at Marange sites, while at a site in Wedza, farmers would get better returns with manure fertilisation on maize.Une enqu\ue9te conduite en champs de ma\uefs et d\u2019arachides chez les petits fermiers a montr\ue9 que des \ue9chantillions de sol des champs de ma\uefs avaient des niveaux de pH, calcium et de phosphate significativement superieurs \ue0 ceux des champs d\u2019arachide. Il a \ue9t\ue9 trouv\ue9 qu\u2019il y avait une utilization limit\ue9e d\u2019engrais mineraux et organiques en champs d\u2019arachide et ceci \ue9tait li\ue9 aux ressources limit\ue9es et aux risques associ\ue9s \ue0 la fertilisation dans un environement \ue0 faible et incertaine pluie. La basse fertilit\ue9 des sols a contribu\ue9 \ue0 la reduction du rendement en arachide. L\u2019efficacit\ue9 agronomique de la fumure organique de vaches complement\ue9e d\u2019engrais phosphat\ue9 sur le ma\uefs et l\u2019arachide, a \ue9t\ue9 \ue9valu\ue9e dans un essai factoriel chez 5 petits fermiers au Zimbabwe. Des rendements \ue9lev\ue9s de ma\uefs et d\u2019arachides ont \ue9t\ue9 obtenus o\uf9 la fumure a \ue9t\ue9 utilis\ue9e jusqu\u2019 \ue0 des taux de 20 t ha-1 dans la majorit\ue9 des sites. L\u2019avantage d\u2019ajouter l\u2019engrais phosphat\ue9 sur la fumure n\u2019a pas \ue9t\ue9 \ue9vident. L\u2019analyse factorielle a montr\ue9 des effects principaux significatifs de la fumure (P<0,01) ensemble pour les effets directs et r\ue9siduels. L\u2019effect principal de la phosphate n\u2019a pas \ue9t\ue9 du tout significatif alors que l\u2019interaction entre la fumure et l\u2019engais phosphat\ue9 a \ue9t\ue9 signifactive. L\u2019analyse de la r\ue9gression a montr\ue9 des effets lin\ue9aires de la fumure sur le rendement du ma\uefs et du rendement en gousses d\u2019arachide. Les differentes qualit\ue9s de la fumure utilis\ue9e dans les different sites (bas\ue9 sur la teneur en azote total du fumier) au raient contribu\ue9 \ue0 la variation des r\ue9ponses observ\ue9es dans les differents sites. L\u2019analyse \ue9conomique pr\ue9liminaire a r\ue9v\ue9l\ue9 qu\u2019il \ue9tait profitable d\u2019utiliser la fertilit\ue9 directe et r\ue9siduelle du fumier \ue0 Murange, alors que les fermiers du site de Wedza pourraient recevoir de meilleurs revenus avec la fertilisation du ma\uefs avec du fumier