Effects of optimal multifunctional growth-promoting bacteria ‘HS3’ on maize and peanut growth in a maize-peanut intercropping system

Objective Multifunctional microorganisms greatly improve crop rhizosphere environment and enhance fertilizer utilization efficiency. This study screened a multifunctional growth-promoting bacteria and verified its ‘yield increasing and quality improving’ effect on crops.

Methods Growth-promoting bacteria were isolated and screened from peanut rhizosphere soil. The species were identified based on morphology, physiology, biochemistry, and 16S rDNA sequence. We used the plate dilution method to achieve the highest indole-3-acetic acid (IAA) producing capacity and organo-P and K dissolvability. Pot and field experiments of peanut-maize intercropping were conducted with and without ‘HS3’ isolation.

Results The strain ‘HS3’ belongs to Bacillus acidiceler. Its IAA production, organo-P and K solubilization capacity were 45.82 mg/L, 2.86 mg/L, and 19.88 mg/L. The optimum culture conditions for the highest IAA production were 30℃, 32 h of inoculation, pH 6, 100 mL/250 mL liquid volume, and fructose and yeast as C and N sources. The optimum culture conditions for the highest organo-P solubility were pH 6, 100 mL/250 mL liquid volume, and sucrose and urea as C and N sources. Compared with no ‘HS3’ isolation control in the pot experiment, ‘HS3’ isolation treatment increased the contents of IAA, available P and K by 80.95%, 14.24%, and 70.59%. It also (P<0.05) increased the growth of the root and shoot of the peanut. In the field experiments, ‘HS3’ inoculation improved IAA, available N, available P, and available K content in peanut soil by 49.06%, 22.64%, 24.01%, 52.89%, and IAA, available P, available K by 67.83%, 22.94%, 14.17% in maize soil, respectively. As a result, ‘HS3’ inoculation decreased the number and weight of blighted fruit per plant by 54.26% and 47.90%, respectively, increased peanut yield by 9.87%, maize yield by 18.56%, and decreased the bald length of maize ear by 27.30%. The results of correlation analysis showed that the soil IAA content, available phosphorus and available potassium were positively correlated with peanut and maize yield.

Conclusions The screened multifunctional probiotic Bacillus acidiceler strain ‘HS3’ showed the prospect of improving soil available P and readily available K content, and promoting the aboveground and underground of plant growth.