Mechanisms of carbon and nitrogen distribution in soil aggregates in response to soil conditioners

Soil conditioner has good performance in improving soil environment and solving soil barrier problems. The purpose of this study was to analyze the effects of different types of soil conditioners on the distribution of soil aggregates and the yield of corn, and to find out the suitable soil conditioners for improving the barren soil in the Yellow River irrigation area. The treatments include no soil conditioner (CK), cow dung organic fertilizer soil conditioner with different organic matter contents (Om-20%, Om-30%, Om-40%, Om-45%), humic acid soil conditioner (Hu-20%) and amino acid soil conditioner (Am-25%). The result indicated that different types of soil conditioners promoted the formation of aggregates with particle size > 0.25 mm, improved the stability of aggregates, and increased the content of organic carbon and total nitrogen in macroaggregates. Compared with CK, the contents of organic carbon and total nitrogen of various soil conditioners in macroaggregates increased by 20.08-48.89% and 8.36-42.86%, respectively. The organic carbon content of macroaggregates under Am-25% treatment was significantly increased by 7.15% compared with Hu-20% treatment. The contents of available phosphorus, available potassium, organic carbon and total nitrogen under Am-25% treatment was increased by 6.37-45.86%, 6.29-22.39%, 3.49-12.05% and 2.64-19.74% than that of cow dung organic fertilizer soil conditioner treatments, respectively. Correlation analysis and structural equation model analysis showed that macroaggregates with particle size greater than 0.25 mm were positively correlated with corn hay yield. Aggregate stability and chemical properties accounted for 71% of corn hay yield changes, and organic carbon mainly affected corn hay yield through soil C/N ratio. Therefore, the application of soil conditioner, especially amino acid soil conditioner, to the barren soil in the Yellow River irrigation area can improve the physical and chemical properties of soil, promote the formation of macroaggregates, improve the stability of aggregates, and promote the high and stable yield of corn.