Effects of Exogenous Organic Matter on Soil Nutrient Dynamics and Its Role in Replacing Chemical Fertilizers for Vegetable Yield and Quality

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Searching for a low-cost soil amendment that can reduce the reliance on chemical fertilizers while maintaining crop yields is a vital issue to sustainable agricultural development. In this study, bio-organic matter derived from harmless disposal of livestock and poultry carcasses was used to discuss its potential for substitute chemical fertilizer. An incubation experiment was conducted by incorporating bio-organic matter into the soil at the rate of 0% (CK), 1%, 2%, 3%, 4%, 5%, 6% and 7% (T1, T2, T3, T4, T5, T6, T7) of soil mass to investigate the effects of bio-organic matter on soil physical properties and the nutrient release dynamics. A pot experiment was conducted with three treatments: 150 mg·kg−1 nitrogen from compound fertilizer (CK), 150 mg·kg−1 nitrogen from bio-organic matter (B1) and 300 mg·kg−1 nitrogen from bio-organic matter (B2), to evaluate the potential of bio-organic matter as a substitute for chemical fertilizers in influencing the yield and quality of Chinese cabbage (Brassica chinensis L.). Results showed that in the incubation experiment, bio-organic matter addition reduced soil bulk density of 1.5% to 8.9% and increased soil porosity by ranging from 1.5% to 10.9%. The soil physical properties were significantly improved when addition rates ≥ 4% (by soil mass). The interaction effects of addition rate and incubation time had a significant effect on soil nutrients. In the pot experiment, substitution of chemical fertilizer with bio-organic matter did not reduce the yield, and the increasing application rate of bio-organic matter led to significantly higher soluble protein, soluble sugar and total phenol content of vegetables. Additionally, nitrite content in the vegetables was slightly lower with bio-organic matter compared to that under CK. It is concluded that bio-organic matter derived from the harmless disposal of livestock and poultry carcasses is feasible; it has great potential to partially or entirely replace chemical fertilizers, thereby contributing to realizing chemical fertilizer reduction.