Effects of Wheat or Rapeseed Cultivation On the Spore Density of Arbuscular Mycorrhizal Fungi and the Growth of Succeeding Soybean.

In this research, we investigated the effects of introduced winter crops on the arbuscular mycorrhizal fungi (AMF) spore density, succeeding soybean AMF colonization rate, growth and yield. From autumn to spring, wheat (Wheat plot) or rapeseed (Rapeseed plot) were grown in experiment field in each year. From spring, soybean plants were grown in all plots. The field experiments were performed from 2007 to 2011, four years. In this period, phosphorus fertilizer was not applied in all plots. And N and K fertilizer was applied for winter crops and soybean cultivation of the all plots. The AMF spore density in soil of rapeseed plot decreased after the cultivation of winter crops in each year. This tendency was remarkable in the third and fourth year. On the other hand, the AMF spore density in soil of wheat plot increased after the cultivation of wheat. And the AMF colonization rate of succeeding soybean in the wheat plot was higher than that in rapeseed plot. The defference of succeeding soybean growth in each plot was not clear in the first and second year, but, in the third and fourth year, it was clear in each plot. For example, the soybean phosphorous absorption, growth, and yield of wheat plot was better than that of rapeseed plot in third and fourth year. These results lead to the conclusion that when the wheat cultivated from autumn to spring, the AMF spore density increased after the cultivation of wheat. And the succeeding soybean growth and yield after the cultivation of wheat was became better than that after the cultivation of rapeseed.