IMPACTS OF RHIZOBIUM INOCULATION AND PLANTING PERIOD ON GROWTH AND BIOMASS PRODUCTION OF SOYBEAN (GLYCINE MAX) IN SOUTH-WESTERN ZONE OF NIGERIA

Abstract

The research was conducted at the biological garden of Emmanuel Alayande University of Education, Oyo, to investigate the impact of rhizobium inoculation and planting period on growth and biomass production of soybean in the South-Western zone of Nigeria. Soybean is the world’s most popular and important legume because of its potential to improve human diet as well as animal feed through supplying of high-quality protein and serves as a source of raw material base for agro-industries. Field experiment was conducted to determine the impact of rhizobium inoculation and planting period on growth and biomass production of soybean. The experimental design was a complete randomized block design in split plot with three replications. This consists of two factors i.e. three sowing dates (T₁, T₂ and T₃) and rhizobium inoculated treatments (T₁R, T₂R and T₃R). Growth parameters (plant height, diameter of stem and number of leaves) were monitored for 8weeks. At maturity, three plants per plot were randomly selected, the whole plant were uprooted, root nodulation and fresh weight were determined; plants were oven dried to constant weight at 70⁰C, weighed and milled to powder. This was later used for proximate and nutrient analyses. All data obtained were subjected to analysis of variance using mixed model ANOVA, LS means or standard errors in mixed models Duncan Multiple Range Test (DMRT) at p =≤ 0.05 level of significant. The results showed that there was significant (p =≤ 0.05) effect of rhizobium inoculation on growth and biomass production of soybean.  Higher growth parameters, and biomass were obtained in the second planting (T₂ = 1^st of August) while the least was obtained in the third planting (T₃ = 22^nd of August). Similarly, soybean grain yield showed significant effects of rhizobium inoculation and planting period with highest grain yield obtained in the (T₂ = 1^st of August). The results of the experiment indicated that early August is the best planting period of soybean in the south-western zone of Nigeria.