Studies on the Polyethylene Mulching Culture of Upland Rice Process of growth and its characteristic

[摘要] In order to study the application of polyethylene mulches to upland rice culture in Kanto District, the whole growth process of the plants was investigated under unmulched and mulched condition. The varieties were upland rice Norin glutinous No. 20 (early-maturing) and Norin glutinous No. 1 (medium-maturing). Upland rices were sown on April 11 and 25 in the mulched plots, on April 25 and May 15 in the unmulched plots, respectively. All fertilizers were applied as base in the mulched plots, but nitrogen was top-dressed in addition to the base fertilizer as that of customary culture under the unmulched plots. The results obtained were as follows. 1. Under mulching culture emerging-and vegetative-period was reduced, because of higher soil temperature, and then, in each variety, the heading time sown on April 25 was advanced 8 days compared with the unmulched plots. Especially the heading time was advanced on the end of July, even Norin glutinous No. 1 which was medium-maturing, when it was sown on the bound period of early seeding under mulching condition. From above results, it can be suggested that the mulching culture of upland rice in Kanto District is usefull to avoid dry-spell damage during the later summer. 2. The leaf emerging velocity of upland rice under mulching culture was earlier, and showed prosperous growth in the early period, and then a number of panicles were formed. The weight of 1, 000 grains and the percentage of ripened grains were inc reased, too. But the number of spikelets per panicle was inferior to the unmulched plots. As a result, the yield of each varieties was not different between unmulched and mulched plots. 3. But upland rice in mulched plots showed shorter leaf blade, smaller leaf-blade·leaf-sheath (including stem) ratio and shorter internode. From these phases of growth, upland rice could utilize sunlight efficiently and had resistance to lodging. And the tendencies were remarkable in early sowing. These facts were due to prosperous growth in the early stage and decreasing nitrogen content in leaves in the late stage. On the basis above mentioned facts, it is suggested that the more increased yield under mulching culture can be obtained accoring to top-dressing before reduction division stage.

[学科分类] 农业科学（综合）