Sesbania cannabina and S. rostrata are grown as green manure crops in Okinawa, Japan. The former sets seeds early and poses a potential weed problem. The latter does not. We compared plant growth and nutrient uptake between the species. S. rostrata showed more vigorous growth in pots than S. cannabina in Kunigami Marji (red soil), Shimajiri Marji (dark red soil), and Andosol at 45 days after sowing. Both appeared to have low P tolerance, because P fertilization had little effect on their growth in Kunigami Marji. The Mg content was higher in S. rostrata, but other nutrient contents tended to be similar or slightly higher in S. cannabina. In the field, S. rostrata showed significantly more vigorous growth than S. cannabina at 87 days. The pods accounted for about 1/3 of the aboveground weight in S. cannabina. The total aboveground weight (including pods) was also large in S. rostrata. The P contents in the aboveground parts (including pods) were similar, but the N, K, Ca, and Mg contents were larger in S. rostrata. These results suggest that S. rostrata would be as effective as S. cannabina as a green manure crop.

Field experiments were conducted in a farmer’s field in Akita Prefecture, from 2017 to 2019 to examine whether a practical amount of seeds can be treated to obtain pre-germinated seeds with elongated roots but not elongated coleoptiles, referred to as root-elongated seeds hereafter, and to examine their seedling establishment and early growth in comparison with pre-germinated seeds and iron-coated seeds. Seed samples, 15 to 48 kilograms in weight, of the cultivars ‘Chihominori’ and ‘Moeminori’ were treated in a steam nursery chamber at 30°C to obtain root-elongated seeds. Seeds with appropriate root lengths were obtained after 36~41 hours of treatment in‘Chihominori’ and after 30~45 hours of treatment in ‘Moeminori’. The root-elongated seeds and pre-germinated seeds were sown with a puddling seeder in flooded paddy fields. Iron-coated seeds were broadcast with a knapsack duster as the conventional practice. The seedlings grown from root-elongated seeds were longer and had higher leaf numbers at the seedling emergence stage than those from the pre-germinated seeds and seedling establishment and growth at the seedling establishment stage were better, although the differences were not statistically significant. The seedlings grown from the root-elongated seeds were longer and heavier and had higher leaf numbers than the iron-coated seeds at the seedling establishment stage. The lodging and yield of the plants grown from the root-elongated seeds were the same as those grown from the pre-germinated and iron-coated seeds. In conclusion, a practical amount of root-elongated seeds could be obtained using a nursery chamber, and seedling establishment and growth in the farmer’s field were improved.

Cultivation of early-maturing lines of Perilla frutescens Britt. var. frutescens is important to avoid damages caused by typhoons and early-frost in the Shidara region of Aichi Prefecture, Japan. In the present study, the characteristics of Nagurazairai, a late-maturing native line cultivated in Shidara region, Kurotane, an extremely early-maturing line and their progeny lines (No. 1, No. 7 and No. 9) raised by the crossing between Nagurazairai and Kurotane were examined along with the effects of the cultivation area on their characteristics. The lines were cultivated at Inabu, a hilly and mountainous area, and Kasugai, a low-altitude flat area, in 2015 and 2016. All breeding lines, which flowered earlier in the order of No. 1, No. 7 and No. 9, flowered earlier than Nagurazairai which flowered in late September. There was little difference in flowering time of all lines between Inabu and Kasugai. No. 1 had the greatest number of seed-setting per flower cluster and the heaviest 1000-seed weight among all lines. All lines of Kasugai had lower yield per plant than Inabu , which was primarily due to the lighter 1000-seed weight in Kasugai than in Inabu. In kasugai, No. 1 and No. 7 showed markedly lower percentage of filled-seed in 2016, probably due to the continuously high temperature condition during the seed-filling stage. The seed oil concentration tended to be lower in early-maturing lines, and was lower in Kasugai than in Inabu, except for No. 1 and Nagurazairai. These results indicate that the lines for cultivation of Perilla in a low-altitude flat area, should have a seed-filling stage not coinciding with the high-temperature season or should be tolerant to high temperatures.

We developed yield-estimation models based on yield trial data for the eight main-consumed rice cultivars in Japan using environmental variables, including soil available N, N fertilizers, air temperature, and solar radiation. The difference between attainable yield and farmers’ actual yield was determined by comparing the model-estimated values and the yield in the statistical yearbook of Ministry of Agriculture, Forestry and Fisheries (MAFF). Yield-estimation models were developed using three calculation methods, i.e., partial least square regression (PLS), random forests (RF), and XGBoost (XGB); and, the effect of data-cleansing treatments was evaluated. The goodness of model fitting for PLS was improved by the data-cleansing treatment, whereas that for RF and XGB was decreased. The calculation method to explain yield variation better differed with the variety. The average rank of feature importance of daily minimum temperature during the reproductive period was the highest in RF and XGB. The significant positive correlation between the model-estimated values and yield in the statistical yearbook of MAFF indicates that these models can explain the yield response to different environments, and shows that the attainable yield is 55.4–57.3 kg 10 a^–1 higher than the farmers’ actual yield in Japan.

An estimation formula to determine the time of barnyardgrass leaf emergence was developed to enable application of herbicides at the appropriate time in dry sown paddy fields. The maximum leaf stage of barnyardgrass was investigated under various conditions such as year, cropping season, and field location including the experimental station fields and local farmer’s fields, and examined using the daily mean air temperature of the Agro-Meteorological Grid Square Data System. The results showed that, in dry sown paddy fields, the growth progress of barnyardgrass from the starting point of herbicide application differed from that of plowing. Therefore, the analysis should be done separately according to the starting point, and the effective accumulated temperature -7 degrees is suitable for estimation. Furthermore, considering that the growth may be delayed due to factors other than temperature, we decided to use only the data above the regression line of the measured leaf stage and the estimated leaf stage when creating the estimation formula. The regression equation calculated from the data was used as the estimation formula. Using the estimation formula, we found that in 96% of all the data, the leaf stage difference between the measured and the estimated, was distributed below +0.5, and the measurement rarely deviated greatly from the estimation. Therefore, the created estimation formula was not considered to be a practical problem in dry sown paddy fields under the various conditions in Chugoku area.

A newly developed early maturing and high palatability rice cultivar Tsukiakari has been disseminated in the Hokuriku region. It showed 10% higher grain yield than an early maturing rice cultivar Akitakomachi. This study aimed to clarify the high-yielding characteristics of Tsukiakari through the multi-environmental testing in the Hokuriku region. A total of 47 yield trials during 2017–2019 revealed that the grain yield of Tsukiakari reached a plateau around 750 g m^–2. From the significant linear regression among grain yield, yield components, and shoot nitrogen content in Tsukiakari, the values obtained were 35,700 spikelets per square meter, 423 panicles per square meter, 83.8% of filled grains, 25.1 g of one-thousand grains, and 14.0 g m^–2 of shoot nitrogen content at a grain yield of 750 g m^–2. The percentage of perfect grains and grain protein content was estimated to be 72.5% and 7.1% at a grain yield of 750 g m^–2 using the significant linear regression with spikelet number per square meter, which was developed using the data set obtained in 2017–2018 and 2017–2019, respectively. Note that the percentage of perfect grains in 2019 was much lower than that in 2017–2018 due to an extremely high temperature during ripening. Calculated culm length of Tsukiakari at a grain yield of 750 g m^–2 was 80.4 cm, and it is expected to avoid lodging at maturity up to approximately 80 cm. Overall results indicate that Tsukiakari is an elite cultivar that can achieve high yield and grain quality without lodging if rice plants are not subjected to an extremely high temperature during ripening.

This study was conducted in the Western Region Agricultural Center (Fukuyama City, Hiroshima Prefecture) to elucidate the changes in feed composition and contents in rice after heading. In 2007, we cultivated a short panicle cultivar, “Tachi-Ayaka” using two different transplanting times. In 2018, we cultivated four short- panicle varieties with different heading dates: “Tsuki-Hayaka”, “Tsuki-Ayaka”, “Tsuki-Suzuka”, and “Tsuki-Kotoka”. We investigated their top dry weight and their feed composition and contents from heading date to about 70 days after heading. The feed composition and contents varied greatly up to 40 days after heading. Specifically, crude protein (CP) and acid detergent fiber (ADF) decreased, crude ash (CA) and hemicellulose hardly changed; and, non-fibrous carbohydrate (NFC) increased. Top dry weight peaked at 30-40 days after heading in all transplanting times and varieties. Increased in weight between heading and 40 days after heading of NFC, hemicellulose and CA accounted for 71%, 19% and 8%, respectively, of that of top dry weight. We conclude that wide variation in feed composition content up to 40 days after heading was mainly due to the increase in NFC dry weight. The feed composition content was stable from 30 days after heading because the variation in NFC dry weight was very small.

The brown rice quality in Akita Prefecture, Tohoku area Japan, decreased in 1999, 2010, and 2019 due to high temperatures during ripening, but the summer in Akita is too short to consider moving the cropping season as a countermeasure for the high temperature. In 2007 and 2010, we planted the rice cultivar Akitakomachi using two paddy transplanting methods; dense planting after a single application of fertilizer in nursery boxes to suppress nonproductive tillers (SNoPT) and uniform basal application of fertilizer to the top-soil and top-dressing at the meiosis stage as the conventional practice (Copr). The maximum temperature was 1.4 - 2.1°C higher in the plastic greenhouse during the ripening period than in the field. In 2007, the temperature was not considered high, but the irradiance was low. In 2010, the temperature was considered high. In SNoPT, the frequency of tillering at the 4-7th nodal position, which results in high yield and quality, was higher than that in Copr. The decrease in leaf color was smaller in SNoPT than in Copr. Furthermore, the percentage of chalky kernels in SNoPT in the field and in the greenhouse was 83% and 80%, respectively, of the values in Copr, although the differences were not significant. The yield and rice protein content in SNoPT were similar to those in Copr. These results suggest that SNoPT could be used as a countermeasure for high temperatures and low irradiance during ripening in the Tohoku area.

Since the survey standard of development in wheat and barley was presented more than 50 years ago, the varieties and cultivation methods have changed greatly and the survey standard differs with the regions. In the present study, the important developmental stages: such as emergence of seedling, double ridge formation, jointing, heading, flowering and maturity were re-defined. The association of these developmental stages with the ambiguous developmental terms such as tillering stage and spike formation stage, and the Zadoks growth scale, which is pervasive abroad was discussed. Then, the varietal and regional differences in development in wheat and barley were illustrated using examples of field experiments conducted in Hokkaido, Tohoku, Hokuriku, North Kanto and North Kyushu.