Grain crop response to contour hedgerow systems on sloping Oxisols

Farming systems that minimize the rate of soil degradation and optimize foo d crop yields are needed to sustain soil productivity on sloping, acid, inf ertile soils in the humid tropics. Research was conducted on two Oxisols wi th slopes ranging from 22 to 30% to evaluate the performance of several con tour hedgerow systems, with and without the addition of 60 kg N ha(-1) per crop, on rice (Oryza sativa) and maize (Zea mays L.) production. Contour he dgerows were double rows of the tree legume Gliricidia sepium (G); Gliricid ia and the native grass Paspalum conjugatum (GPas); Gliricidia and an exoti c fodder grass Penisetum purpureum (GPen); double rows of Penisetum (Pen); and a conventional open field (C) farming system without hedgerows. Glirici dia prunings and all crop residues were applied to the soil surface in the alleys, but Penisetum was harvested. Food crop yields in all hedgerow treat ments tended to be less than the Control for the first two years, presumabl y due to the displacement of land planted to the food crop. In the third an d the fourth years, the rice and maize yields of Treatments G and GPas exce eded the Control, most consistently when N was not applied. Penisetum,il re duced food crop yields regardless of N application presumably due to nutrie nt removal in the fodder. The results indicate that Gliricidia in a contour hedgerow increases food crop yield on strongly acid Oxisols by recycling n utrients and partially supplementing the N demand by the food crops.