Y. Li, C.-h. Huang, L. Zhu, and Y. Zhang (PR China)
Soil compaction, water, nitrogen leaching, water quality protection, and Hydrus–1D
With steady increases in agricultural mechanization in the Taihu Lake Basin, China, the changes of plough pans in farmland and consequent widespread losses of water and nutrients are an increasing concern. The influence of soil compaction on the leaching of water and nitrogen (N) was tested using soil column experiments and model simulation (Hydrus-1D model). Four soil compaction treatments (no compaction, NC; weak, WC; medium, MC and strong compaction, SC) were applied, producing bulk densities of 1.46, 1.56, 1.63 and 1.70 g/cm3 , respectively. The leaching flux of water decreased with increased soil compaction, and there was a corresponding increase in surface runoff. At the same time, there were changes in N transport and transformation due to both the effects of water movement and the consequent oxidation–reduction in soil. In our experiments, at the same levels of irrigation and fertilization, the compaction treatments of WC, MC and SC, resulted in the amount of N leaching through the bottom of the soil column accounting for 25.6, 20.3 and 14.5% of total added N from the surface soil, respectively; the corresponding surface runoff losses accounted for 3.6, 10.6 and 18.3%. Breaking the plough pan (NC) resulted in no surface runoff, but N leaching through the bottom was a relative maximum, accounting for 29.0% of the total added N. These show that high compacted soil of plough pan will beneficial to reduce the leaching amount of N into groundwater, but increase the risk of N loss through surface runoff into surface water, especially during rainy season in Taihu Lake Basin.
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