杨-农复合系统土壤养分分布特征

以2年生杨-农复合系统为研究对象，通过对不同林分结构（密度、配置方式）杨-农复合系统及农田土壤养分的分布特征进行分析比较，探讨林分结构对杨-农复合系统土壤养分的影响规律。结果表明：（1）杨-农复合系统土壤含水率、pH值、有机质、全氮、全磷和全钾含量在0～20 cm和20～40 cm土层均存在明显的水平差异，但距杨树树行不同距离点土壤养分的变化规律性不明显，可能受杨树根系分布、土壤微生物、施肥以及耕作等的影响；3种模式杨-农复合系统土壤含水率、pH值均高于对照，全氮含量仅树干基部土壤低于对照，而全磷、全钾含量与对照间差异不明显；（2）4种类型土壤含水率、pH值、有机质、全氮、全磷和全钾含量在上下层间呈极显著差异(P<0.01)，存在明显的垂直分布规律，且M₁模式上层土壤含水率、pH值、有机质、全氮含量高，全磷与全钾含量低，M₂与M₃模式多相反。

Distribution characteristics of soil nutrient in poplar-crops agroforestry system

The distribution characteristics of soil nutrients under different stand structures (in the 2-year-old poplar-crops agroforestry system) was studied. The results showed as follows. (1) The soil moisture content, pH value, organic matter, total nitrogen, total phosphorus, and potassium content at soil depths of 0-20 cm and 20-40 cm in poplar-crops agroforestry system had an obvious horizontal difference, but it was not obvious that the regularity of change of soil nutrients in different distances from poplar stem, which might be affected by the root distribution of poplar, soil microorganism, fertilization and soil tillage; In three poplar-crops agroforestry systems, soil moisture contents and pH values ??were higher than those of the control group; the total nitrogen content in the base of trunk was lower than that of the control group; total phosphorus and total potassium were not significantly different from those of the control group; (2) The difference of moisture content, pH, organic matter, total nitrogen, total phosphorus and total potassium content in four types of soil between the lower layer and the higher layer was highly significant (P<0.01). There were obvious vertical distribution, and the soil moisture content, pH, organic matter, total nitrogen content in upper soil in M₁ mode was higher, while the total phosphorus and total potassium contents in upper soil in M₁ mode were lower, which were opposite in M₂ and M₃ modes.