黄土区不同施肥对土壤颗粒及微团聚体组成的影响

采用野外采样与室内分析方法，运用颗粒体积分形理论，研究了15年长期不同施肥处理对黄土区农田土壤颗粒组成、 微团聚体分布及有机碳的影响。结果表明，施肥处理对020 cm土层影响较大，不同施肥处理土壤颗粒及微团聚体的优势粒级均为0.02~0.05 mm。有机肥（M）、 磷肥（P）、 有机肥和氮肥配施（MN）、 有机肥、 氮肥和磷肥配施（MNP）处理可显著提高020 cm土层0.1~0.2 mm土壤颗粒的百分含量，有机肥和磷肥配施（MP）以及MNP处理有利于该土层大粒径土壤微团聚体的形成。氮肥和磷肥配施（NP）处理的土壤分散率最大，M处理最小。不同施肥处理土壤颗粒体积分形维数差异不显著。相关性分析表明， 020 cm及2040 cm土层土壤颗粒体积分形维数与粘粒（0.002 mm）和细粉粒 （0.002~0.02 mm） 呈极显著正相关，与粗粉粒 （0.02~0.05 mm） 和细砂粒 （0.05~0.2 mm）极显著负相关; 土壤团聚度与0.05 mm各粒径土壤团聚体显著或极显著负相关，与 0.05 mm各粒径土壤团聚体显著或极显著正相关。020 cm土层土壤有机碳与0.01~0.05 mm各粒径土壤团聚体显著或极显著负相关，与0.1~0.5 mm各粒径土壤团聚体极显著正相关。

Effects of long-term fertilization on soil particles and microaggregate distribution in the loess area

Based on the particle volume fractal theory,  effects of 15 years fertilization on soil particle distribution,  microaggregate distribution and organic carbon content of farmland in the loess area were studied using field sampling and experimental analysis. Results show that the fertilization has a significant effect on the particle and microaggregate distribution in 0-20 cm soil layer,  and the fractions of 0.02-0.05 mm are predominant in different treatments. The organic fertilizer (M),  phosphoric fertilizer (P),  the combination of organic and nitrogen fertilizer (MN),  and the combination of organic,  nitrogen and phosphoric fertilizer (MNP) significantly improve the contents of 0.1-0.2 mm fractions,  and. the combination of organic and phosphoric fertilizer (MP) and MNP treatments are contribute to the formation of large soil microaggregate. Among the treatments,  the biggest dispersion rate is found in the treatment of nitrogen and phosphoric combination (NP),   the smallest  in the M treatment. There are no significant differences among  treatments. The soil particle fractal dimension is positively correlated with clay particle (<0.002 mm), and fine silt (0.002-0.02 mm) and negatively correlated with coarse silt (0.02-0.05 mm) and fine sand (0.05-2 mm). The soil aggregate degree is negatively correlated with <0.05 mm aggregate and positively correlated with >0.05 mm aggregate. The  soil organic carbon is negatively correlated with in 0.01-0.05 mm microaggregate and positively correlated with 0.1-0.5 mm microaggregate in 0-20 cm layer.