长期施用化肥条件下土团聚体中有机碳与养分分布

目的]探究长期施肥与小麦—玉米轮作下(蝼)土表层水稳性团聚体组成及对团聚体中有机碳和养分分布的影响,为评价长期施肥对改善(蝼)土肥力状况的影响提供科学依据.方法]利用田间长期施用化肥与轮作定位试验,通过湿筛法分离土壤水稳性团聚体,得到土壤团聚体构成,并测定不同粒径团聚体中有机碳和养分的含量.结果]结果表明长期施用化肥显著影响土壤水稳性团聚体含量,长期施肥降低了＞2 mm的水稳性团聚体数量,增加了＜1 mm的水稳性团聚体含量.施肥在一定程度上提高了水稳性团聚体有机碳的含量,但施用高量氮、磷下0.25～0.5 mm和＜0.25 mm水稳性团聚体中有机碳含量明显低于施用低量氮、磷肥料.不同施肥处理土壤水稳性团聚体全氮含量变化趋势与水稳性团聚体有机碳含量基本一致.磷素在不施肥处理各粒径团聚体中均匀分布,低氮、磷处理各粒径团聚体中全磷含量差异较小,高氮、磷处理各粒径土壤团聚体中全磷含量变化无明显趋势.长期施肥降低了＞2 mm水稳性团聚体中全K含量,增加了＜2 mm的水稳性团聚体中全K含量.结论]水稳性团聚体关系土壤有机碳、氮的数量,水稳性团聚体及其中有机碳、氮含量在氮磷化肥的长期施用下变化无明显规律,并且,长期施用氮、磷化肥下土壤磷素和钾素在土壤中的保存及供应能力也受到影响.因此,需要合理施肥管理,促进农田生产力的可持续发展.

Distribution of Organic Carbon and Nutrients in Water Stable Aggregates of Lou Soil Under Long-term Application of Chemical Fertilizer

Objective] Studing the effects of long-term-fertilization in wheat-corn rotation field with Lou soil on water stable aggregates and soil nutrient distribution in different sizes of aggregates, to provide a scientific basis for the evaluation of long term-fertilization on its improvement effect.Methods] The wheat-corn rotation field with long-term application of chemical fertilizer was selected as the study site. The composition of aggregates was analyzed using the wet sieve method. Contents of organic carbon and nutrients in different sizes of aggregates were measured.Results] Long-term application of chemical fertilizers significantly affected soil water stable aggregate contents. Long-term fertilization reduced the contents of >2 mm soil water stable aggregates, but increased <1 mm soil water stable aggregate contents. To a certain extent, the amount of organic carbon in water stable aggregates increased, but the organic carbon contents of 0.25~0.5 mm and <0.25 mm soil water stable aggregates under high nitrogen and phosphorus treatments were significantly lower than that of the low nitrogen and phosphorus treatment. The changing tendencies of contents of total nitrogen in soil water stable aggregates were essentially in agreement with organic carbon in soil water stable aggregates under different fertilization treatments. Distribution of phosphorus in different size soil water stable aggregates was even in no fertilization treatment. The difference of phosphorus content in each size soil water stable aggregate was insignificant under low nitrogen and phosphorus treatment, while the trend in high nitrogen and phosphorus treatment was not obvious. The total potassium contents of >2 mm soil water stable aggregates decreased due to long-term application of chemical fertilizer, whereas total potassium contents of <2 mm soil water stable aggregates increased under long-term application of fertilizer.Conclusion] Soil water stable aggregates influenced the quantity of soil organic carbon and nitrogen. The contents of soil water stable aggregates, soil organic carbon and nitrogen of soil water stable aggregates varied irregularly under long-term application of nitrogen and phosphorus fertilizers. In addition, conservation and supply capacity of phosphorus and potassium in soil were affected by long-term application of nitrogen and phosphorus fertilizers. Therefore, reasonable use of chemical fertilizers and management were needed to improve the soil structure, maintain soil fertility and promote the sustainability of farmland productivity.