Response of Inoculated soybean nodulation, growth and yield to inorganic fertilizer (soil and foliar application)

Abstract

The need for a balanced nutrient supply for soybean cultivation at various growth stages cannot be underestimated. Reason being that research has confirmed that despite the ability of legumes to fix atmospheric nitrogen, it requires some level of nutrient to start up with at the initial vegetative stage when the roots are yet to be well established, especially in low soil fertility areas. More so at certain growth stages soybean leaves experience senesces and nodule rupture. Therefore, there is need to supply balanced nutrients so as to sustain soybean growth at those critical periods of it’s development. Hence, on-station trials (Nyankpala) were conducted at the experimental fields of CSIR-Savannah Agricultural Research Institute (SARI), to ascertain the effectiveness of some commercial fertilizers (soil applied inorganic (NPK), foliar applied inorganic (Boost-Extra) and bio-fertilizer (Bradyrhizobium japonicum) for improvement of soybean productivity in the Northern savannah zone of Ghana. Eight treatments were used for each study site; T1=Boost Extra (BX), T2=BX+Bradyrhizobium japonicum (INO), T3=25 kg N+30 kg P2O5 + 30 kg K2O ha-1(NPK), T4=NPK+INO, T5=INO+NPK+BX, T6= NPK+BX, T7= INO and T8=Control which were laid out in a Randomized Complete Block Design (RCBD) replicated four times. Consistent significant (P<0.05) response of soybean nodule number, nodule dry weight, shoot biomass yield, pod number, pod weight and grain yield increase (101 and 90%) in 2012 and (76 and 66%) 2013 to the combined application of INO+NPK and INO+NPK+BX respectively, over the sole application of each of the fertilizers and the Control, and in some cases INO+BX. This is an indication that indeed the use of combine fertilizers applied to soybean at different growth stages and different application mediums (soil, foliar and seed) are paramount in soybean cultivation in the study area. The application of sole foliar fertilizer (BX) gave the best yield in 2012 which was 103% increase more than the control.