Effects of fertilizers containing Bacillus subtilis on photosynthesis of soybean leaves and soil enzyme activities

In order to reduce chemical fertilizers in soybean production and conserve the black soil, we conducted a field experiment including following treatments: special compound fertilizer (CK), Bacillus subtilis + amino acid granular fertilizer (T₁), Bacillus subtilis + fulvic acid potassium fertilizer (T₂), Bacillus subtilis + seaweed refined powder granular fertilizer (T₃), straw Bacillus subtilis decomposed organic fertilizer (T₄), and chicken manure Bacillus subtilis decomposed organic fertilizer (T₅).The effects of various fertilizers on soybean photosynthesis and soil enzyme activities were comprehensively evaluated.The results showed that, as for photosynthetic parameters, the net photosynthetic rate of T₁, T₄, and T₅ increased by 5.0%, 0.7%, and 8% compared with CK, without significant differences among the treatments.The maximum and minimum values of transpiration rate were T₅ and T₂, which was 30% higher or 43.1% lower than that of CK, respectively.The stomatal conductance value was in the order of T₅>T₄>T₁>CK>T₃>T₂, and significant differences were found among T₂, T₃, T₅ and CK.The concentration of intercellular CO₂ in T₂ was with the smallest value, significantly lower than CK by 12.0%, while that of T₁ and T₅ was 5% and 7% higher than CK.The chlorophyll contents in T₄ and T₅ were significantly lower than that of CK; T₁ was with the maximum value of chlorophyll a content, 17.3% higher than that of CK.The chlorophyll b content in T₂ increased by 2% compared with CK, while T₃ had no effect.The soil urease activity in each treatment was significantly higher than that of CK, and T₅ was with the maximum value, 17.7% higher than that of CK.The activity of soil invertase was in the order of T₁>T₃>CK>T₅>T₄>T₂, and 18.9% increase in T₁ but 27.8% decline in T₂ compared with CK.T₃ had the minimum value of soil alkaline phosphatase with 8.55 mg · g^-1, while T₄ had the maximum value, which was 7% higher than that of CK.As environmentally friendly fertilizers, Bacillus subtilis + amino acid granular fertilizer, straw subtilis spore-decomposed organic fertilizer and chicken manure subtilis spore-decomposed organic fertilizer would replace chemical fertilizers partially, with potential application in the future.