长期有机无机肥配施条件下的旱地红壤水分特征分析

Soil Moisture Characteristics Analysis of Upland Red Soils as Affected by the Long-term Application of Organic-inorganic Fertilization

以长期有机无机肥配施条件下的旱地红壤为研究对象,采用压力膜法测定土壤水吸力在1~1500 k Pa条件下的旱地红壤含水量变化,绘制出完整的土壤水分特征曲线;运用van Genuchten模型对实验数据进行拟合并计算出旱地红壤中不同类型水分的含量,借助相关分析探讨了土壤团聚结构、土壤有机质、铁铝氧化物与黏粒等土壤理化性质与旱地红壤中各类型水分常数间的相关关系。结果表明:长期配施有机肥的旱地红壤水分含量均随着土壤水吸力(0~1500 k Pa)的增加呈现出"快速下降-缓慢下降-基本平稳"的变化趋势;配施有机肥虽然可显著提高旱地红壤中的饱和含水量,但同时也使旱地红壤中的多余水显著提高,且可显著降低全有效水占饱和含水量的比例。相关分析表明,旱地红壤游离氧化铝、有机质分别与正常生育有效水、速效水及全有效水呈显著正、负相关关系。这一结果意味着旱地红壤中游离氧化铝含量越高、有机质含量越低,越利于旱地红壤中有效水量的提高,但背离了"有机质增加可以提高土壤供水能力"的这一通识。因此,有必要明确并区分铁铝(氢)氧化物与有机质在红壤团聚结构的形成及土壤保水功效调控过程中的作用与机制,进而为旱地红壤水分的有效调控提供科学的依据。

Soil-water characteristic curves of the upland red soils under the long-term application of organic-inorganic fertilizers were determined by the pressure membrane method in the lab. Van Genuchten model was used to simulate the water curve data and calculate the soil moisture constants. The correlations between soil physicochemical properties(such as soil aggregation structure, organic matter(OM), free iron-aluminum oxides and clay) and the soil moisture constants were analyzed. Results showed that soil water contents in all treatments changed in the tendency of 'falling fast'-'slow droping'-'stable changing' with the increasing of the soil water suction(0 ~ 15 bar). Combination of organic manure application could increase not only soil saturated water contents, but also the contents of superfluous water in the upland red soils, while significantly decrease the proportion of total effective water to the soil saturated water. Correlation analysis showed that there were significantly positive correlations between soil free aluminum oxide(f-Al2O3) with the normal-fertility water(NFW), quick-acting water(QCW) and all effective water(AEW), respectively,while the influences of organic matter were in contrast to f-Al2O3. These results indicated that high content of f-Al2O3 and low content of organic matter were favorable for the improvement of effective water in the upland red soils. But organic matter was generally considered to increase soil water supply capacity. Therefore, it is necessary to clearly distinguish the functions and mechanisms between iron and aluminum(hydrogen) oxides and organic matter in the soil aggregate structure formation and water conservation in the studied region, which can provide scientific basis for the effective soil water regulation.