EFFECT OF FOUR BIOCHAR TYPES AND INORGANIC PHOSPHATE FERTILIZER ON GROWTH AND NODULATION OF SOYBEAN (GLYCINE MAX (L.) MOENCH)

Abstract

There is a compelling need to explore the use of biochar as a sustainable alternative to the use of chemical or mineral fertilizer amendment in the contexts of soybean cropping system in Sub-Sahara Africa. A pot experiment was conducted to evaluate the effects of poultry manure biochar (PB), swine dung biochar (DB), maize cob biochar (MB), saw dust biochar (SB) and inorganic phosphate fertilizer (single supper phosphate) applied singly on the growth and nodulation of soybean in Minna, southern Guinea savanna zone of Nigeria. The biochars were applied at four levels of 0, 5, 10, and 15 t ha-1 while single supper phosphate (SSP) was applied at 30 kg P ha-1. The experimental design was a completely randomized design (CRD) with three replications. The results showed that soybean plant parameters of height, number of leaves, number and dry weight of nodules, shoot, root and total dry biomass increased in all treatments that received animal waste biochars (PB & DB) over the non-treated control (0 t ha-1) except the plant root length and shoot/root ratio. However, the difference was statistically significant (p<0.05) only at the higher application level of 10 t ha-1. Plant-based biochars (MB & SB) were less beneficial to soybean plant, and their influence on soybean parameters did not differ significantly from non-treated control. Soybean plant also responded positively to the application of SSP but was significantly better than the control only for plant height. The results showed that animal waste-derived biochars were more beneficial to soybean plant in terms of nodulation and growth than the plant-based biochars and SSP fertilizer. Evidence that soyabean growth, biomass accumulation and nodulation benefit more from amending soil medium planted to soyabean with manure based biochars applied at 10 tons ha-1 compared to the plant-based biochar showed that, manure base biochars are more suitable as soil amendments for legumes like soyabean that require more P and less amount of N in their nutrition.