RESPONSE TO RHIZOBIA INOCULATION OF SOYBEAN (Glycine max I.) AND PHOSPHORUS FERTILIZATION IN ROTATION WITH MAIZE (Zea mays L.)

Abstract

This study was conducted at Nyankpala in the Guinea savanna zone of Ghana during the 2014 and 2015 cropping seasons to assess the performance of soybean and maize in a rotation system. In season one, using randomized complete block design the treatments were untreated control (sole soybean), rhizobia inoculation, phosphorus application, rhizobia inoculation + phosphorus and sole maize (2 different plots). In the second season, the first season experimental plots served as main plot and were divided into four sub-plots on which maize were planted and treated with four NPK rates (30-30-30, 60-30-30, 90-30-30 and 120-30-30 kg/ha) in a split plot design. The experiments were replicated three times. Residual soil N and P modified by NPK application, and their effect on growth and yield of maize and soybean were assessed. The results showed that soybean production led to significant increases in residual soil nitrogen content of about 16 kg/ha to 55 kg/ha, which is about 8 to 28 folds higher than that observed in maize fields. The level ofN was enhanced with inoculation. The application ofP to maize during the first cropping season of maize-soybean rotation led to increases in residual P levels of soils which might have positive impact on yield of soybean that was grown in the second season. Grain yield of maize that followed soybean in a rotation system performed better than maize that followed maize when NPK was applied. This showed that the residual N might have helped maize crop when low rate of N (30 kg/ha) was applied. Phosphorus applied to maize in the first season enhanced the performance of sole soybean sowed in the second season. It is recommended that in maize soybean rotation phosphorus application could be avoided. Similarly, application of 60 kg N/ha to maize that follows soybean production in a rotation system could make much economic sense in the Guinea savanna zone and promoted.