RESPONSE OF COWPEA (VIGNA UNGUICULATA L (WALP) AND SOYBEAN (GLYCINE MAX, L. MERRIL) TO RHIZOBIA INOCULATION IN THE GUINEA SAVANNAH ZONE OF GHANA

Abstract

Series of field experiments were undertaken in the Guinea Savanna agro - ecological zone of northern Ghana to assess the influence of three bradyrhizobium strains BR3262, BR3267 and BR3299 from (EMBRAPA) and legumefix (from South Africa) as biofertilizer products in optimizing cowpea and soybean production. The field experiments were carried out using six treatments in the cowpea field and five treatments in the soybean field at SARI, as an on - station experimental field during the 2013 and 2014 cropping seasons. The treatments were replicated four times using randomized complete block design. On farm cowpea experiments were carried out in 20 farmers field at Adibo, Pion, Walayi, Duko and savelugu. And soybean was carried out at Tingoli, Sanga, Tunayi1i, Savelugu and Yendi as field adaptive trials on 20 farmers field. Soil chemical properties evaluated in the study areas before trial establishment indicated that the soil fertility status was below the optimum for cowpea and soybean growth. The results showed that the use of inoculants as biofertilizer 5g per 10 kg of seed is essential to increase cowpea and soybean yields in the study area. Grain yields of 2115 and 1862 kg ha I were recorded respectively for inoculation of BR3262 and control field at on station in cowpea. Inoculation of cowpea enhanced yield 53% more than the control treatment. Furthermore, the use of legumefix did significantly (P<O.05) enhance grain yield in soybean, yielding 56% more than the control. However the best enhancing treatment of soybean grain yield were inoculation + 60 kg P20S ha-I + 30 kg K20 ha-I which had the highest grain yield of 2,583.3 kg ha' at on station. Bradyrhizobium strain inoculum treatments increased nodule number, nodule fresh weight and nodule dry matter accumulation by 53%, 62.7% and 62.5% respectivciy relative to the control in cowpea at 35 days after sowing (DAS). Moreover, rhizobium strain inoculants (legumefix) treatment increased nodule number, nodule fresh weight and nodule dry matter accumulation by 87%,86.8% and 84.7% respectively relative to the control in soybean at 35 DAS nodulation. However the best treatment enhancing nodule dry matter accumulation at 35 DAS was inoculation (legumefix) + 60 kg P20S ha' + 30 kg K20 ha' given 90.8% over the control. The emphasis on the benefit of inoculation is good but it is more beneficial combining more than one nutrient or treatment at a time as clearly observed in this studies, In soybean for efficient grain yield it best to use inoculation (legumefix) + 60 kg P20S ha" + 30 kg K20 ha". And for total dry matter accumulation it is good to use 25 kg N ha" + 60 kg P20S ha" + 30 kg K20 ha' in northern Ghana.