Effects of tillage method, fertilizer, and crop rotation on population dynamics of soybean cyst nematode (Heterodera glicines) and soybean growth

摘要

Recently, damages by soybean cyst nematode (SCN) are increasing in Japan, due to continuous cultivation of soybean, and the establishment of the culture method to control SCN is awaited. In this research, field experiments were conducted over four years. Various tillage methods were combined with fertilizers (chemical fertilizer, compost of cattle droppings and calcium cyanamide) and crop rotation with non-host and trap crops (corn, crotalaria, and red clover) to investigate their effects on the population dynamics of SCN and soybean yield. Shallow tilling (plowing depth : 5 cm) decreased the SCN population to a lower level than conventional tillage (plowing depth : 15 cm). It was attributed to fewer disturbances of soil and the presence of larger number of natural enemy microorganisms in the shallow tillage treatment. The effects of fertilizers on SCN were not clear. The effect of the preceding crop plant was greater than that of the tilling method. Corn cultivation before soybean increased SCN population drastically under the conventional tillage, but not under the shallow tillage. Suppressive effects of crotalaria and red clover on SCN remained during the following soybean cultivation, especially red clover cultivation with the shallow tillage kept SCN population under 10 eggs/g of dry soil. Soybean yield was increased by the application of calcium cyanamide and cattle manure. Consequently, it was suggested that the shallow tillage would be advantageous to decrease the SCN population, and to promote the suppressive effects of non-host or trap crops, such as corn, crotalaria, and red clover.