Polyvinylpyrrolidone (PVP) and Na-Alginate Addition Enhances the Survival and Agronomic Performances of a Liquid Inoculant of <i>Bradyrhizobium japonicum</i> for Soybean (<i>Glycine max</i> (L.) <i>Merr.</i>)

Abstract

Nontoxic polymers PVP and Na-alginate may provide a favorable environment for the survival of bacteria. Therefore, PVP and Na-alginate were added to a growth medium to develop a liquid inoculant of Bradyrhizobium japonicum strain. The strain was identified by 16S rDNA sequencing. The addition of PVP (1.8%) and Na-alginate (0.2%) in the medium promoted a better survival (1.93 × 109 cells mL−1) of B. japonicum strain compared to the control (3.50 × 102 cells mL−1) after 6 months of storage. The combination of PVP and Na-alginate ensured 1.53 × 107 cells mL−1 up to 12 months of storage under ambient temperature (28 ± 2 °C), whereas PVP (1.8%) or Na-alginate (0.2%) alone produced similar cell counts only up to 8 months and 6 months, respectively. Consecutive field experiments proved the efficacy of the liquid inoculant on nodulation and yield of soybean. The combination of PVP and Na-alginate-based inoculation of B. japonicum strain significantly increased the nodule number per plant, number of pods per plant, number of seeds per pod, seed yield, and yield per hectare (p ≤ 0.05). Thus, the combination of PVP- and Na-alginate-based inoculation of B. japonicum has great potential to popularize the organic cultivation of soybean.

Keywords

• <i>Bradyrhizobium japonicum</i>
• biofertilizers
• soybean
• nodulation
• crop yield