Stability of soil structure in response to cations‐carbon‐microbial linkages with manure application in the coastal saline‐alkaline soil, China

Abstract Manure application is confirmed to improve the stability of aggregates, while the effects derived from soil cations, organic carbon (OC) functional groups and microbial abundance are still unclear, especially in the saline‐alkali soil. We designed a field experiment with the addition of 0, 500, 1000 (medium‐rate C) and 2000 (high‐rate C) kg OC ha −1 to explore it in the Yellow River delta. The results showed that manure application increased soil aggregate stability. The dispersed charge with exchangeable Na + and exchangeable K + decreased, whereas the soil particle bonding bridge with exchangeable Ca 2+ , exchangeable Mg 2+ , free Fe (ferrum)‐oxides, free Al (aluminium)‐oxides and available Si (silicon) increased with manure application. OC was increased in soil in medium‐rate C and high‐rate C treatments; polysaccharide‐C was 11.5% and 13.20%, aliphatic‐C was 18.2% and 20.0% and aromatic‐C was 20.0% and 15.6%. Aliphatic‐C and aromatic‐C contributed 72.6% and 7.0% variation of soil aggregates, respectively. Manure application increased the abundance of bacteria and fungi; this was conducive to soil macroaggregate formation. However, the highest microbial abundance decomposed part of OC at high‐rate C input, resulting in no significant improvement in the stability of aggregates over medium‐rate C treatment. Therefore, appropriate manure application can supply the bonding of soil inter‐particles with cations, promote the retention of OC and enhance the abundance of the microbial community, which is crucial for improving the structural stability of saline‐alkali soil.