长期施肥条件下土壤生物量氮的动态及其调控氮素营养的作用

本文研究了棕壤定位试验13年后的土壤生物量氮变化及氮素营养作用。结果表明,长期施用有机肥或化肥均能增加土壤生物量氮数量,尤以有机肥的作用明显。生物量氮的基础含量能够反映土壤供氮能力大小,其季节变化主要受施肥,土壤温度和水分等因素影响,不同施肥区生物量氮周转期为0.25～0.52年,其中以低量有机肥与氮肥配合周转速度快,其周转为0.25年,当季不施肥区周转期较长,平均0.45年。微生物体提供的氮量中大部分来自活化土壤中的有机氮,其中单施氮肥区微生物体供氮量大于作物吸氮量;施用氮磷化肥区微生物供氮量与作物吸氮量基本相等;施用氮磷钾化肥微生物体供氮量仅占作物吸收量的75.1％,与当季不施肥区接近。不同施肥区微生物体供氮量与作物吸收氮量及产量之间存在明显的正相关关系。

CHANGE OF SOIL BIOMASS-N AND ITS ROLE IN ADJUSTING-CONTROLLING NITROGEN NUTRITION UNDER LONG-TERM FERTILIZATION CONDETIONS

This paper dealt with the changes of microbial biomass-N and its role in nitrogen nutrition through a 13-year field experment with different fertilizer treatmants on brown earth. Results showed that long term application of NPK fertilizers or manure could increase soil biomass-N, especially the effect of manure on biomass-N was obvious. The basic content of biomass-N (before fertilizer application) could reflect the capacity of offering N by soil. The seasonal fluctuation of biomass-N was mainly affected by applying fertilizer, soil temperature, soil moisture and other factors. The turnover period of biomass-N was between 0.25 and 0.52 year in different fertilizer plots, in which application of N fertilizer with low amount of manure the turnover period was 0.25 year and in which current plots without fertilization the turnover period was 0. 45 year in average. The amount of offering N by biomass-N was mostly from active organic N in soil. In Single N fertilizer plots the amount of offerng N by biomass was higher than that of N uptake by crop; in NP fertilizer plots the both was equal to same and in NPK fertilizer plots the amount of offering N by biomass was lower than that of N uptake by crop. There existed a close relationship between the offerng N by biomass and the uptake of N by crop and yield in various fertilizer plots.