Abstract:

Soil aggregate is an important part of the soil ecosystem, and can affect the physical, chemical and biological properties of soil. Its stability is the result of the combined action of binders and dispersants. To explore the effects of binders and dispersants on the stabilization mechanism of soil aggregates, the authors selected 10 main zonal soil types across the country (black soil, red soil, yellow brown soil, dark brown soil, purple soil, chestnut soil, loess soil, fluvo-aquic soil, brick red soil and aeolian sand soil) as the research objects, screened soil aggregates by wet sieving method and conducted the measurement and analysis. The results showed that in the aggregate distribution of the 10 soil types, the content of large aggregates in brick red soil (> 0.25 mm) was the highest, which was 86.77%, followed by that in black soil, which was 76.13%; the content of large aggregates in fluvo-aquic soil was the least, only 42.85%. The content of aggregates >2 mm and of 0.5-1 mm had the greatest influence on the distribution of aggregates. The organic matter content of black soil was 46.06 g/kg, significantly higher than that of other soil types, followed by that of brick red soil. The difference of soil organic matters was most significant when the aggregate size was <0.053 mm, and the organic matter trend was the same as the whole soil when the aggregate size was >2 mm. Chestnut soil had the highest exchangeable sodium content among the 10 soil types, which was 234.48 mg/kg, followed by fluvo-aquic soil with the content of 177.08 mg/kg. On the whole, the organic matter content was positively correlated with the stability of soil aggregates (r=0.615), exchangeable sodium content was negatively correlated with soil aggregates (r=-0.391), and the significant correlation between organic matter and the stability of aggregates was obvious on the aggregate size of 0.053-0.25 mm. The stabilization of soil aggregates was caused by the combined action of organic matter and exchangeable sodium, increasing the same unit of organic matter and exchangeable sodium, the stabilizing effect of organic matter on aggregates was 10 times the dispersion effect of exchangeable sodium. In order to better protect the soil, organic fertilizers with relatively low sodium content should be used in agricultural production to reduce the damage to the soil structure by human activities.

Key words: aggregate, organic matter, dispersant, binder, exchangeable sodium, average weight diameter