Effects of Combined Practice of Nitrogen Application Regime with Sparse Planting on the Growth and Yield of Rice.

Varietal Differences in Tillering and Yield Responses of Rice Plants to Nitrogen-Free Basal Dressing Accompanied withSparse Planting Density in the Tohoku Region of Japan

“…In previous studies, Hirano et al (1997) and Truong et al (1998) reported that two cultivars Akitakomachi and Hitomebore, produced a greater number of tillers m -2 in CONT than in BNo. The present study showed that the numbers of total, primary and secondary tillers m -2 were also much smaller in BNo than in CONT for all 12 cultivars and lines ( Fig.…”

“…These farmers practiced a specifi c cultivation, in which the early growth of rice plants was controlled by the omission of nitrogen fertilizer at transplanting time and by sparse planting density (13 to 17 hills per m 2 ), and later growth was promoted by nitrogen topdressing after the 8 th leaf age stage (BNo). By this method, the total amount of nitrogen fertilizer applied was smaller, the planting density was lower, and grain yield was 5-10% lower than that in the conventional cultivation (CONT) in normal years (Hirano et al, 1997).…”

“…Previous studies (Hirano et al, 1997) indicated that a smaller number of tillers m -2 resulting in a smaller number of panicles m -2 was one of the main reasons for the lower yield in BNo. In the study on the effect of planting density and nitrogen top-dressing on the growth and yield of rice plants in BNo, Truong et al (1998) suggested that increased planting density could not improve yield, but that the top-dressing of nitrogen fertilizer at the neck node initiation stage (33 to 35 days before heading) could increase grain yield up to 95-100% of that in CONT through increasing the number of panicles on the secondary tillers and the number of spikelets per panicle.…”

“…Rice plants grown by this method produce a large number of tillers and spikelets per unit area, and give a high grain yield under favorable weather conditions (Matsushima, 1995;Hirano et al, 1997). The application of heavy nitrogen fertilizer at the early growth stage, however, sometimes causes overluxuriant growth at the middle growth stage resulting in lodging and low percentage of ripened grains, subsequently leading to a reduction in grain quantity and inferior quality (Yoshida, 1981;Tanaka, 1983;Hashikawa, 2001).…”

“…The main part of damage was sterility due to cool weather around the young microspore stage, and the rest was damage by blast disease and others (Oyamada, 1995;Nishiyama, 1996). Although most farmers in the Tohoku district suffered from heavy yield loss due to cool weather, interestingly, some of them obtained grain yields comparable to the amount in normal years (Murata et al, 1994;Hirano et al, 1997). These farmers practiced a specifi c cultivation, in which the early growth of rice plants was controlled by the omission of nitrogen fertilizer at transplanting time and by sparse planting density (13 to 17 hills per m 2 ), and later growth was promoted by nitrogen topdressing after the 8 th leaf age stage (BNo).…”