Long-term manure and straw addition enhance protistan diversity and stimulate soil microbial interactions and nutrient mineralization in vegetable field

Abstract

Fertilization is crucial for agriculture as it influences yield and soil quality by regulating soil structure, nutrient transformation, and microbial interactions. This study aimed to examine how long-term organic fertilization affects protists and microbial interactions in regulating nutrient turnover in soil aggregates. Compared to chemical fertilizers application, manure and straw addition increased the contents of soil organic carbon (C), total phosphorus (P), dissolved C, mineral nitrogen (N), and available P due to a higher proportion of large macroaggregates. Manure and straw addition enhanced enzymes activities for acquiring C, N, and P, and alleviated microbial N limitation. The enzyme activities of C and P-acquiring was higher in microaggregates, whereas N-acquiring enzyme was higher in large macroaggregates. Manure and straw addition significantly boosted protistan diversity and exhibited the highest connectivity and stability of the protistan-bacterial-fungal network. Mainly bacterivores, omnivores, and phototrophs significantly correlated to organic C, and mineral N. Further, organic fertilization positively correlated with microbial network stability and enzyme activity, whereas aggregate size has negative effect. Stable microbial networks positively influenced enzyme activity and the availability of dissolved C and nutrients. Overall, integrating chemical fertilizer, manure, and straw application can boost protistan diversity and stabilize microbial networks, enhancing nutrient availability, which offers insights for improving soil fertility and crop productivity.