Studies on the control of the barnyard grass in the paddy field (2)

Abstract

1. As continuing works of this series, several ecological investigations and tests on the control of the barnyard grass were made. 2. In the paddy fields in Kurashiki Region, Japan, we found that the barnyard grass, Nobie (Echinochloa crusgalli BEAUV) consisted of 3 varieties : namely, Hime-inubie (var. Prat-icola OHWI), Ke-inubie (var. caudata KITAGAWA) and Ta-inubie (var.oryzicola 0HWI) of type (a) with pubescent sheath and type. (b) with smooth sheath, the latter predominating in the district. 3. In the laboratory, it was bound that with the increase in the depth of water, the germination of the seeds of barnyard grass decreased, excepting Ta-inubie, but when a good drainage was provided after submerging, these seeds germinated well. 4. Most barnyard grasses died after having been submerged in water at the depth of 20 cm.for 15 to 30 days. At 15 cm. it took 30 days, but many survived after 15-20 days, and also same was true at l0 cm. for 15 to 30 days. 5. Barnyard grass developed best on the water-saturated soils, but a good stand was obtined when submerged at a depth of 5 cm. 6. On the other hand, rice plants showed considerable tolerance to water. The growth and yield of the plants grown with water of l0 to 20 cm. deep, equalled that grown with 5 cm. deep water which was taken as the control, except those plots in which the plants 1odged. 7. The growth of rice plants on the water saturated soil was poor, as it was suppressed by the luxuriantly growing weeds, and resulted in a poor yield.