营养元素对连作大豆减产的控制功能

通过实验室和田间微区试验方法，连续三年研究结果表明：连作大豆在受到有害生物危害和大豆残茬腐解物中间产物的毒害抑制时，其根系的吸收和运输营养物质及固氮能力均减弱或部分丧失。此时，增加营养元素在土壤中浓度，可达到胁迫吸收的功效，弥补损失。连作大豆增施氮肥，可比不施氮最高增产97．7％。经不施磷最高可增产89％；施钾与不施钾比，最高增产可达26％。施用微量元素，亦能提高产量，与对照相比，施锌增产16．9％，施锰增产13．2％，施硼增产1．4％，施钼增产4．6％，施镁增产14．6％。

Controlling function of nutrition element on soybean continuous cropping

Three-year experiment was made both in lab and plot. The results showed that the nitrogen fixation ability of the roots would get weaken or lose partly as continuous soybean was injured by the harmful creature or the intermediate products of the decomposed matter from soybean root. At this time, increasing the concentration of nutrition in soil would force the absorption of root, and make up the loss. The yield of continuous soybean with N application was higher than that without N application by 97.7%. There were 89% of the yield with P application higher than that without P application. In contrast with no K application, the yield of continuous soybean with K application increased by 26%, and Zn by 16.9%, Mn by 13.2%, B by 1.4%, Mg by 14.6%.