Improving maize (Zea mays L.) growth and yield using Jatropha (Jatropha curcas L.) seed cake under Zimbabwean soil condition

A research study exploring the use of jatropha seed cake as a sole source of nutrients and used in combination with inorganic N fertilizer was conducted on station at Henderson Research Station on sandy and clayey soils during the rainy season of 2006/2007. Two experiments were conducted to determine the effect of jatropha seed cake on maize dry matter and grain yield and its effect on weed density and biomass. Experiment 1 explored the use of jatropha seed cake rates ranging from 767kg/ha to 3835kg/ha in maize production. Included in the experiment were three other treatments viz extension recommendation for inorganic fertilizer, farmer¡¦s practice of applying cattle manure and a control. A Randomized Complete Block Design (RCBD) was used and a total of 8 treatments were assessed. Jatropha seed cake application rate and inorganic fertilizer had higher yields (P „T 0.05) on maize dry matter yield at 4, 8 and 12wace on the sandy soil site. Application of 2301kg/ha of jatropha seed cake and the extension recommendation resulted in maize dry matter yields of 3059kg/ha and 3399kg/ha respectively at 12wace. There were no differences noted in maize dry matter yields on the clayey soil site. Weed densities of the following species F exilis and Eragrostis spp (sandy soil site ) and T. annua, C. rotundus, and L. martinicensis (clayey soil site) were significantly reduced (P<0.05) where jatropha seed cake was applied. Weed biomass on the sandy soil site was reduced by 30% along the maize rows. In experiment 2, three levels of jatropha seed cake were tested (0, 767kg/ha and 1534kg/ha) in combination with 3 levels of inorganic nitrogen levels (0, 25kg/ha and 50 kg/ha N) The N was applied as topdressing at 6wace. The other treatments included use of 200kg/ha Compound D (N: 7%, P:14% and K: 7%) as basal fertilizer in combination with the three inorganic N fertilizer rates. 12 treatments were tested in this experiment and it was laid out as a 3 x 3 factorial arranged in an RCBD design. The jatropha seed cake levels performed equally as well as the inorganic fertilizer treatment in terms of dry matter yield at 4 and 8 wace. The maize grain yield was significantly higher (P<0.05) were jatropha seed cake was applied (954kg/ha and 1036kg/ha) for the 767kg/ha and 1534kg/ha rates. The control had lower grain yield (538kg/ha). The interaction between the jatropha cake rate and inorganic N rate was not significant (P>0.05). The results from this study suggest that smallholder farmers can apply jatropha seed cake at a rate of 767kg/ha in maize production and 25kg/ha inorganic N can be used as a top dressing fertilizer.