长期地膜覆盖对土壤氮素状况的影响

EFFECT OF LONG-TERM COVERING WITH PLASTIC FILM ON CHARACTERISTICS OF NITROGEN IN SOIL

定位试验结果表明,长期地膜覆盖对棕壤全氮影响较小,而碱解氮含量平均下降6.46mg/kg。覆膜土壤上层NO^-_3—N含量明显增加。有机氮各组分在覆膜条件下发生较大变化,其中氨基酸态氮的绝对和相对数量下降显著,各处理平均下降21.6mg/kg和2.0％。覆膜使土壤微生物体氮量增加。试验结果还表明,施用有机肥和化肥都能提高土壤全氮、碱解氮、NO^-_3—N和有机氮的含量,施用有机肥明显地提高了微生物体氮的含量,是培肥覆膜土壤氮素肥力的有效措施。

This experiment was conducted in a loamy brown earth derived from loesslike parent material at Shenyang Agricultural University during 1987 ~ 1994. The main results showed that the average contents of alkali-hydrolyzable-N (1mol NaOH-N) and aminoacid-N in all covered treatments declined 6.46mgkg-1 and 21.6mgkg-1, compared with uncovered treatments. However, no significant effect was found on total N, NO3-N tended to be accumulated in the top layers of the plots covered with the plastic film, because of much water with soluble NO3 moving toward these top horizons. Soil biomass-N increased greatly by covering practice, which could lead to the improvement for soil nitrogen supplying ability. In addition, the application of organic manure could improve the levels of total N, alkali-hydrolyzable-N, NO3 -N and organic components of nitrogen in soil. Therefore, more manure should be applied to soil covered with plastic film so as to improve covered soil fertility.