Abstract
South African soils generally lack native Bradyrhizobium strains that nodulate and fix atmospheric nitrogen (N2) in soybeans (Glycine max L.). It is therefore very important to inoculate soybeans with products that contain effective Bradyrhizobium strains as active ingredients. In this study, a field experiment was conducted on two bioclimatic zones in South Africa during the 2019/2020 season to assess the effect of Bradyrhizobium japonicum strain WB74 inoculant formulation on nitrogen fixation, growth and yield improvement in soybeans. The first bioclimatic zone was characterized by a sandy clay loam soil, whereas the second bioclimatic zone has a sandy loam soil. The results showed that inoculation of soybeans with both peat and liquid formulations of Bradyrhizobium japonicum WB74 increased nitrogen uptake, which resulted in yield increase. The amount of N fixed was measured as 15N isotopes and increased with all treatments compared to the uninoculated control in both liquid and peat inoculant formulations. In bioclimatic zone A, slightly better results were obtained using the liquid formulation (1.79 t ha−1 for liquid compared to 1.75 t ha−1 for peat treatments), while peat formulations performed better in bioclimatic zone B (1.75 t ha−1 for peat compared to 1.71 t ha−1 for liquid treatments). In both areas higher yields were obtained with the formulations used in this study compared to the registered standards (treatment T3). The findings in this study provide vital information in the development and application of formulated microbial inoculants for sustainable agriculture in South Africa.
Highlights
Soybean (Glycine max L.) is one of the most important annual grain legumes in the world and is currently produced at a higher rate in the USA, Brazil, Argentina, China, andIndia [1]
Nitrogen uptake was higher with T2 and T3 in both liquid and peat formulations, and bioclimatic zones
The increase in nodule formation in B. japonicum inoculated plants led to the increase in nitrogen fixation which results in the improvement in soil health
Summary
Soybean (Glycine max L.) is one of the most important annual grain legumes in the world and is currently produced at a higher rate in the USA, Brazil, Argentina, China, andIndia [1]. Projections have shown that the amount of land allocated to commercial soybean production will increase in the coming decades when compared to the current production area [5]. This will be because of the everincreasing demand for the use of the crop for both human nutrition and as well as a feed an ever-increasing local industrial demand for soybeans for agro-processing [6]. Commercial farmers are becoming cognizant of the benefits of soybean in crop rotation systems with maize, contributing to its increase in production. Commercial farmers are becoming cognizant of the benefits of soybean in crop rotation systems with maize, contributing to its increase in production. [7]
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