Enhancement of Green Soybean Growth and Yield in Alluvial Soil by Potent N₂-fixing Rhizospheric Bacteria

Vo Thi Bich Thuy, Le Thanh Quang, Le Vinh Thuc, Tran Ngoc Huu, Le Thi My Thu, Le Thi Huynh Nhu, Do Thi Xuan, Ly Ngoc Thanh Xuan, Nguyen Hong Hue and Nguyen Quoc Khuong

Background and Objective: Nitrogen fertilizer causes adverse effects on the environment aspect, so biological nitrogen sources should be applied in agriculture. The objective of the study was to evaluate the efficacy of N₂-fixing rhizospheric bacteria in improving soil fertility, nitrogen (N) uptake, growth and yield of green soybean (Glycine max (L.) Merr). Materials and Methods: The pot experiment was conducted with 9 treatments (i) 100% N of recommendation of fertilizer formula (RFF), (ii) 85% N, (iii) 70% N, (iv) 55% N, (v) 85% N and a mixture of Enterobacter cloacae ASD-07 and ASD-28, (vi) 70% N and a mixture of ASD-07 and ASD-28, (vii) 55% N and a mixture of ASD-07 and ASD-28, (viii) 0% N and ASD-07 and ASD-28, and (ix) 0% N, without bacteria, with four replications in in-dyke alluvial soil collected from Chau Phu District, An Giang Province. Results: The use of a mixture of the two N₂-fixing rhizospheric strains as biofertilizers at 85% N level improved NH₄⁺ content and N uptake with an increase of 3.1 mg kg^–1 and 95.8 mg pot^–1, respectively. They also produced higher values in growth including plant height, number of leaves, stem diameter and yield components including pod number, pod diameter, seed length, seed diameter and seed thickness. Conclusion: The application of a mixture of the two N₂-fixing rhizospheric strains resulted in replacing 15% N of RFF, but it still improved the yield.

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