Alley cropping groundnut with Gliricidia sepium in Côte d'Ivoire: effects on yields, microclimate and crop diseases

Abstract

Despite its economic and nutritional importance, groundnut (Arachis hypogaea L.) has received little attention in alley cropping research. Groundnut was grown in rotation with rice and maize during two successive years in an alley cropping experiment with Gliricidia sepium (Jacq.) Steud. (Fabaceae) on a Ferralic Cambisol/Plinthic Lixisol in the semi-deciduous rainforest zone of the Cote d'Ivoire. Drought caused low groundnut yields in both years. Hedgerows at 5 m spacing between the rows increased groundnut yields in the alleys by increasing pod numbers per plant and fully compensated for yield losses due to the surface occupied by the hedgerows and (in the first year) yield depressions at the tree-crop interface. Yield increases were presumably mainly due to reduced disease incidence and improved water relations of the crops. Fertilization increased yields of groundnut straw in the second year, but not pod yields. Root barriers between hedgerows and crops had no effect on groundnut yields. Shading from the hedgerows was limited to the first groundnut row at the southern side of the alleys and to a short period at maturity, and pod yields were consequently not affected. Potential evapotranspiration was lower in the alleys than in sole cropping plots during most of the cropping season, with the most pronounced reductions near the southern tree-crop interface. In the first year, a severe virus infestation of groundnut seemed to be reduced by hedgerow integration. In the second year,Gliricidia mulch reduced the incidence of fungal leaf diseases (late leafspot, rust) of groundnut both under sole cropping and alley cropping conditions. In contrast, leaf destruction by fungi was increased in the shaded parts of the alleys. In alley cropping, effects on crop diseases have to be considered when hedgerows are managed for reducing crop transpiration. Agroforestry may have a potential for increasing yield security of groundnut by reducing transpiration and crop diseases in drought years.