Effects of moisture regime and weeding frequency on growth and yield of upland rice

Abstract

Low Soil moisture and weed competition are often cited as factors which seriously Lf.mi t; the production of upland rice. A study was conducted to investigate the effect of moisture regime and weeding frequency on ,growth and yield of upland rice variety under Kenyan conditions. Experiments were~ carried out at Ahero irrigation Research Station~ between October 1978 and June 1979. An upland variety IR 442-2-58-2-1-2 was used in the experiments. The moisture~ regime treatments consisted of flooding,· intermittent irrigation and rainfed treatments. The results showed that flooding -increased growth and yield of rice more than when ~t was subjected to intermittent irrigafion or rainfed conditions. The effect of flooding was shown·to increase shoot dry matter, plant height, yield components and enhanced early flowering. The variety thus appeared more adaptable to flooding than rainfed conditions. Weeding frequency was composed of Wt W2,W3

and W4 treatments where Wl was weeded at 8,20 and 40 days, W2 at 8 and 40 days, W3 at 20 and 40 days after transplanting. W4 was unweeded control. Treatments Wl and W3 produced higher tiller number, more shoot dry weight, higher LAI and more grain yield than W2 and W 4 . This showed that weeding at 20 days after transplanting (as in Wl and W3) is more important than any other time of the growing period. Weed competition was more serious under intermittent irrigation and rain conditions than flooded .condition. It appears therefore that upland rice would require more vigorous weed control than ~flooded rice especially between 20 and 40 days after transplanting.