Influence of combined application of bioorganic fertilizer and chemical fertilizer on lettuce growth and soil environment

Irrational fertilization leads to soil degradation and output decline, and crop waste disposal affects the sustainable development of environment and resources. Bioorganic fertilizer showed outstanding advantages in plant growth promotion and soil fertility cultivation, which is beneficial to efficient utilization of resource and reduction of chemical fertilizer application, as well as the development of vegetable industries. In this study, bioorganic fertilizers specifically for experiment were made by fermentation after inoculating Bacillus licheniformis, B. amyloliquefaciens and B. megaterium into Chinese medicine residues, respectively; and lettuce pot experiment in greenhouse was conducted to explore the influence of bioorganic fertilizer combined with chemical fertilizer on lettuce growth and soil environment. Six treatments were set, including three treatments of bioorganic fertilizer with 80% nitrogen content replacing chemical fertilizer (B. licheniformis + Chinese medicine residue organic fertilizer + chemical fertilizer, B1H; B. amyloliquefaciens + Chinese medicine residue organic fertilizer + chemical fertilizer, B2H; and B. megaterium + Chinese medicine residue organic fertilizer + chemical fertilizer, B4H), one treatment where organic fertilizer with 80% nitrogen content replacing chemical fertilizer (Chinese medicine residue organic fertilizer + chemical fertilizer, H) and chemical fertilizer treatment (CF), as well as no fertilizer treatment (CK). The growth indicators of lettuce, and soil environmental indicators and bacterial diversity were measured and analyzed. The results showed that: the comprehensive effect of fertilization measures on lettuce yield and quality, soil nutrient environment improvement were both ranked as B4H>B2H>B1H>H>CF>CK. Compared with H, the fresh weight and content of chlorophyll, vitamin C and soluble sugar of lettuce in B4H were increased by 10.69%, 17.77%, 47.54% and 10.95%, respectively; while the nitrate content in B4H was decreased by 52.00%. The contents of available phosphorus (AP), available potassium (AK), microbial biomass carbon (MBC) and water dissolved organic carbon (DOC) in B4H were increased by 47.57%, 10.98%, 35.54% and 16.10% respectively. The bacterial species richness and diversity increased by 7.68% and 0.85% respectively in B4H. Soil AP, AK and available nitrogen (AN) were the main factors affecting lettuce growth, while pH, AP and AK were the main regulatory factors on soil bacterial community. Fertilization was beneficial to bacterial Alpha diversity promotion in lettuce rhizosphere soil, and higher bacterial Alpha diversity in rhizosphere soil performed promoting effect on lettuce yield and quality. As a whole, B4H was the optimal fertilization to the improvement of lettuce growth and soil environment. This study proposed new theoretical support to the development of vegetable and bioorganic fertilizer industries, and was conducive to the implementation of green sustainable development strategy.