Effect of nontilled cropping on drought injury of upland rice

The effects of non tillage on drought injury of upland rice was studied in Andosol upland fields. In 1988, 1990, and 1992, upland rice (cv.Toyohatamoc hi) was grown on nontilled and tillaged upland fields. In 1990 and 1992, be cause of little rain in the summer, drought injury caused a yield reduction in upland rice. But damages were not so serious in nontilled cropping. In nontilled plots, the onset of heading was earlier, and surface soil was dri ed slower than in the tillaged plots in the summer. In the heading stage, d ry matter of top and root length density in the nontilled plot is more than in the tillaged plot. We supposed that the period of drought stress on upl and rice was shorter in the nontilled plot before heading compared with the tillaged plot, since the soil water was retained more.