农田向农林复合系统转变过程中土壤物理性质的变化

Changes of soil physical properties during the conversion of cropland to agroforestry system

以渭北黄土区农林实践中被广泛采用的核桃-小麦间作复合模式为研究对象,以两物种的单作系统为对照,研究单作农田向农林复合系统转变对土壤物理性质的影响,为农林复合系统经营管理和模型的建立提供理论依据.结果表明:核桃-小麦间作对土壤物理性质的改善作用主要发生在0~40 cm土层.核桃-小麦间作可以避免表层(0~20 cm)土壤容重升高,同时在20~40 cm土层对单作农田形成的犁底层也有显著的改善作用.核桃-小麦间作对各土层田间持水量均表现出持续的改善作用,除在20~40 cm土层略低于核桃单作外,其他从第5年开始均高于两单作系统.核桃-小麦间作对各土层土壤孔隙度均存在持续的改善作用,在0~20和20~40 cm土层与两单作系统相比存在显著差异,同时也能提高毛管空隙度的比例.农田向农林复合系统转变过程中对土壤容重、田间持水量、土壤孔隙度均有持续的改善作用,且对浅层土壤的改善作用强于深层土壤.

To provide theoretical basis for modeling ence of conversion of cropland to agroforestry system and managing agroforestry systems, the influon soil physical properties was investigated via a walnut （Juglans regia） -wheat （ Triticum aestivum） intercropping system, a wide spreading local agroforestry model in northern Weihe River of loess area, with the walnut and wheat monocuhure systems as the control. The results showed that the improvement of the intercropping system on soil physical properties mainly appeared in the 0-40 cm soil layer. The intercropping system could pre- vent soil bulk density rising in the surface soil （0-20 cm）, and the plow pan in the 20-40 cm soil layer could be significantly alleviated. The intercropping system had conti-nuous improvement on soil field capacity in each soil layer with the planting age increase, and the soil field capacity was higher than that of each monoculture system in each soil layer （ except 20-40 cm soil layer） since the 5th year after planting. The intercropping system had continuous improvement on soil porosity in each soil layer, but mainly in the 0-20 and 20-40 cm soil layer, and the ratio of capillary porosity was also improved. The soil bulk density, field capacity and soil porosity obtained continuous improvement during the conversion of cropland to agroforestry system, and the improvement on soil physical properties was stronger in shallow soil layer than in deep soil.