Establishment rate of direct-seeded rice in the relay-intercropping system in Kanto region of Japan

Abstract

The relay intercropping system for cultivating direct-seeding rice and winter cereal is a low-cost method particularly for double cropping, because it eliminates the steps of raising seedlings, paddling, and transplanting. However, in this system, the seedling establishment rate (SER) of rice is low and unstable. The objective of this study was to identify the factors affecting SER to highlight the ways to improve SER. Experiments were conducted in experimental fields in Tsukuba City, Ibaraki Prefecture in 2015 and 2016. To determine the time of rice seed death and to calculate seed survival rates, 'Akidawara' seeds were embedded in soil (depth: 3 cm) and dug up after defined periods. We then analyzed the correlation between SER and meteorological factors at two sites (Ibaraki Prefecture and Gunma Prefecture) over the same two years. Based on mean air temperature (MT), we divided the period from seeding to June 20 (when irrigation had been initiated in almost all the fields) into four phases. In Phase 1, the number of days with rainfall (≥5 mm) and soil-wetting days (water potential ≥ −100 kPa) were significantly and negatively correlated with SER. We found that most of the seed deaths occurred after germination, and the germination rates were presumably affected by water absorption during the low temperature phase. Further investigations are needed to understand the occurrences during the seedling emergence period. This study contributes to a better understanding of the factors affecting variations in the SER of direct-seeded rice grown in the relay-intercropping system. List of Abbreviations: DSR: direct-seeded rice; SER: seedling establishment rate; TT: thiuram treatment; SSR: seed survival rate; DS: dead seeds; AGS: already germinated seeds; DSRI: direct-seeding of rice in the inter-row spaces of winter cereals; VWC: volume water content; WP: water potential ARTICLE HISTORY

Seed coating by biofertilizer containing spores of Bacillus pumilus TUAT1 strain enhanced initial growth of Oryza sativa L.

“…Currently, we are developing an inoculation method for sowing rice directly in the field using the Monster Rice 1 cultivar and a biofertilizer containing B. pumilus TUAT1 (Kikuichi) for the agricultural reconstruction of the Hamadori area in Fukushima Prefecture. This method will be less laborious and a low-cost approach for growing rice for feed (Furuhata et al, 2006(Furuhata et al, , 2015Okamura et al, 2018;Shiratsuchi et al, 2016). One of the strategies for direct sowing is to use coating materials that have been developed to obtain a stable establishment of rice plants in the field (Kaufman, 1991).…”

Non-puddling rice cultivation increases subsequent soybean yield in a rice–soybean rotation system

“…Omitting puddling can reduce labor and fuel costs, and irrigation water input, for land preparation for rice establishment (Hossen et al, 2018). Furthermore, direct seeding eliminates the necessity of raising seedlings and transplanting those (Okamura et al, 2018). However, there have been no reports to date on the effects of nonpuddled rice cultivation on subsequent soybean yield under the rice-soybean rotation system used in Japan.…”