Effects of nitrogen fertilizer solution on stability of soil aggregates underdifferent fertility levels

Chemicals can greatly influence the aggregation of soil stability. The effects of NH4Cl solution on stability of cultivated soil aggregates in Guanzhong area were studied. Soil aggregations were analyzed under dry sieving and sulfurous wet sieving conditions. Soil mean weight diameter, geometric mean weight diameter composition of soil aggregates and percentage of aggregate chemical destruction were calculated. The results indicate that under the dry sieving and wet sieving conditions, the percentages of ＞0.25 mm soil aggregates are significantly increased with the increase of soil fertility, while the waterstability of the tested soil aggregates is low. The percentage of ＜0.25 mm soil aggregates is larger than 85%, while the content of agricultural valuable waterstable aggregates(1-5 mm) is only 2.80% in high fertility soil, 1.47% in middle fertility and 0.84% in low fertility. Concentration of NH4Cl solution influences composition of soil aggregates, the contents of 2-5 mm soil aggregates are increased with the increase of NH4Cl concentration relatively, and the contents of 0.25-2 mm soil aggregates are increased significantly. In conclusion, soil aggregations under different fertility levels are greatly different, and both soil fertility level and concentration of salt solutions can influence chemical stability of soil aggregates. Soil aggregates composition focus to 0.25-2 mm with the increase of concentration of NH4Cl solution, which results in homogenization of soil aggregates. Relative to the high fertility soil, middle and low fertility soils are affected more severely by the nitrogen fertilizer solution.