The improper disposal of vegetable waste often leads to the risk of non-point agricultural pollution. In order to enhance our understanding of how soil quality and successive tomato production respond to the anaerobic incorporation of vegetable residues, greenhouse experiments were conducted in 2019 and 2020.
The fresh tomato residues, approximately 17 tons per hectare from greenhouses, were incorporated with carefully selected decomposing agents "Yuandongli" and "Sumao" at three different levels. The results revealed a significant increase in both the Soil Quality Index (SQI) and crop yield at the crop harvest stage for the tomato residues incorporation group, ranging from 7.4% to 24.50% and 2.3%–14.9%, respectively, compared to the control group. Specifically, the levels of soil organic matter (SOM), available phosphorus (AP), available potassium (AK), microbial biomass carbon (MBC), and microbial biomass nitrogen (MBN) increased significantly with the anaerobic incorporation of vegetable residues by an increase of 4.5%–12.3%, 4.1%–31.0%, 2.3%–17.8%, 7.8%–29.2% and 20.0%–35.7%, respectively, compared to the control group.
Additionally, enzyme activities such as soil sucrase, urease, and alkaline phosphatase were averagely enhanced by 38.9%, 28.35 and 48.6%. Moreover, the incorporation of tomato residue led to a significant decrease in both the amount of soil fungi and plant parasitic nematodes, with reductions ranging from 28.8% to 58.2% and 401.% to 85.6%, respectively, at the time of crop harvest.
The direct and indirect effects of soil properties on SQI and subsequent crop yields were evaluated using a structural equation model. It was found that the contribution of soil properties, including SOM, amount of plant parasitic nematodes (APN), MBC, and AP, to driving changes in SQI accounted for 79%. Furthermore, these indexes explained 49% of the variance in crop yield. Although the type of decomposing agent had varying effects on soil properties, it had a negligible impact on SQI.
Furthermore, both SQI and tomato yield did not exhibit a continuous response to the quantity of decomposing agents applied. Our findings suggest that the recommended dosages of the decomposing agent in the instructions are cost-effective and reasonable. The direct anaerobic incorporation of vegetable residues, particularly under greenhouse production conditions, could serve as an efficient and environmentally friendly management strategy for tomato residues.
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