Cultivation of soybean with winter-type barley living mulch in Tohoku region of Japan

Abstract

For operation without herbicide and intertillage of soybean in Tohoku region of Japan, we investigated the effect of a winter-type barley living mulch system on weed suppression, growth and yield of soybean in 2002 and 2003. Treatments were LM+H+ (using both living mulch and herbicide), LM+H+ (using living mulch only), LM -H+ (using herbicide only), LM+H- (no treatment; using neither living mulch nor herbicide), and CC (conventional cultivation ; using herbicide and mechanical intertillage). In the barley living mulch plots (LM-H+ and LM+H-), barley (cv. Benkeimugi) drilled interrow just after soybean (cv. Tachinagaha) seeding in late May emerged 3 days earlier than soybean. Barley had a higher plant height than soybean until late June. The leaves of barley started to yellow early in July, and died early in August. In the barley living mulch plots, weeds were markedly suppressed without the use of herbicide or mechanical intertillage. In 2003, the weed suppression in the barley living mulch plots (LM+H+ and LM+H-) seemed to be better than that in the LM-H+ plot. Weed dry weight in the LM+H- plot was heavier than that in the LM +H+ plot. We concluded that the weed growth was suppressed more effectively by combining living mulch and herbicide. At harvest time, dry weight of soybean in the barley living mulch plots was the same as that in CC in 2002, and smaller than that in CC in 2003. In both years however, soybean yield in the barley living mulch plots was as high as that in CC, and the number of ripening pods and the hundred grain weight in the barley living mulch plot were not significantly different from those in CC. We wish to assume that the mechanical intertillage and the herbicide management would not be necessary in the barley living mulch system, although the risk of soybean lodging might be somewhat increased.