Paddy Soil Stability and Mechanical Properties as Affected by Long-Term Application of Chemical Fertilizer and Animal Manure in Subtropical China

Wet stability, penetration resistance （PR）, and tensile strength （TS） of paddy soils under a fertilization experiment for 22 years were determined to elucidate the function of soil organic matter in paddy soil stabilization. The treatments included no fertilization （CK）, normal chemical fertilization （NPK）, double the NPK application rates （2NPK）, and NPK mixed with organic manure （NPK＋OM）. Compared with CK, Fertilization increased soil organic carbon （SOC） and soil porosity. The results of soil aggregate fragmentation degree （SAFD） showed that fast wetting by water was the key fragmentation mechanism. Among the treatments, the NPK＋OM treatment had the largest size of water-stable aggregates and greatest normal mean weight diameter （NMWD） （P ≤ 0.05）, but the lowest PR and TS in both cultivated horizon （Ap） and plow pan. The CK and 2NPK treatments were measured with PR 〉 2.0 MPa and friability index 〈 0.20, respectively, in the Ap horizon, suggesting that the soils was mechanically unfavourable to root growth and tillage. In the plow pan, the fertilization treatments had greater TS and PR than in CK. TS and PR of the tested soil aggregates were negatively correlated to SOC content and soil porosity. This study suggested that chemical fertilization could cause deterioration of mechanical properties while application of organic manure could improve soil stability and mechanical properties.

湿稳定性，穿入抵抗(PR ) ，和在为 22 年的一个授精实验下面的水稻土的张力的力量(TS ) 决心阐明在水稻土稳定的土壤有机物的功能。处理没包括授精(CK ) ，正常化学授精(NPK ) ，两倍 NPK 申请率(2NPK ) ，和 NPK 与有机肥料(NPK+OM ) 混合了。与 CK 相比，增加的授精玷污器官的碳(SOC ) 和土壤孔隙度。土壤总数破碎度(SAFD ) 的结果证明快走水路弄湿是关键破碎机制。在处理之中， NPK+OM 处理有水马厩总数和最大的正常吝啬的重量直径(NMWD ) 的最大的尺寸(P ≤ 0.05 ) ，但是在栽培地平线(Ap ) 和犁平底锅的最低 PR 和 TS。CK 和 2NPK 处理与 PR > 被测量 2.0 MPa 和脆弱索引 < 0.20 分别地，在 Ap 地平线，建议土壤对根生长和耕种机械地不利。在犁平底锅，授精处理比在 CK 有更大的 TS 和 PR。测试土壤总数的 TS 和 PR 否定地被相关到 SOC 内容和土壤孔隙度。当有机肥料的申请能改进土壤稳定性和机械性能时，这研究建议化学授精能引起机械性能的恶化。