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

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 x 10(9) cells mL(-1)) of B. japonicum strain compared to the control (3.50 x 10(2) cells mL(-1)) after 6 months of storage. The combination of PVP and Na-alginate ensured 1.53 x 10(7) cells mL(-1) up to 12 months of storage under ambient temperature (28 +/- 2 degrees 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.

Automated summary

The study showed that using PVP and Na-alginate as substrates can improve the survival rate and storage time of Bradyrhizobium japonicum strains, thereby significantly increasing the nodule number and yield of soybean in field experiments.