Abstract
Low levels of N continue to limit the production of maize (Zea mays L.) in northern Ghana. One of the strategies adopted to address the situation and to reduce the elemental N requirements is intercropping cereals with legumes to make use of the nitrogen fixed by legumes in the system. A field experiment was conducted on the Nyankpala farm of the Savanna Agricultural Research Institute (SARI) in northern Ghana to assess the influence of date of planting mucuna (Mucuna sp.) on maize grain yield and soil N in maize-mucuna intercropping system in 1996-98. The experiment was laid out as a randomized complete block design with our replications, and comprised five treatments, viz., three dates of interplanting mucuna in maize at 6, 8, and 10 weeks after planting (WAP) maize and two cropping systems, bush fallow (BF) and sole maize (no mucuna) as the control. The results showed that mucuna interplanted at 6 and 8 WAP maize increased soil N by 30% in each case and organic matter was also raised by 38, 39, and 48% for 6, 8, and 10 WAP maize, respectively. Maize grain yields obtained after two years of interplanting mucuna was highest under 6 WAP followed by 8 WAP and the least came from 10 WAP. However, the maize grain yield obtained from 8 WAP was not significantly (P > 0.05) different from the control. The unfertilized maize grain yield under 6 WAP was superior to the yields obtained from the other treatments due to the beneficial effects of the decay of the higher mucuna biomass produced in that treatment in the previous years. Some management of mucuna biomass to ensure it does not smother the cereal crop in association, is necessary to reduce competition for light in favour of the maize crop.
