The application of lime nitrogen (LN) after harvesting rice effectively controls volunteer- and weedy-rice growth, but the effects of LN vary greatly depending on field management conditions and environmental conditions. Varietal differences, the presence or absence of rice straw residue, the temperature and season of LN application, and soil moisture, and rainfall, as well as the tilling time, are factors that influence the effects of LN. For example, rice straw halves the LN effect, moderate water is required, and the LN effect increases along with temperature. A no-tillage period of 2 weeks or more after LN application is required, and immediate tilling after LN application does not suppress volunteer-rice growth. Based on these findings, the concepts and points to consider when using LN are summarized here. The effects of LN application are evaluated in comparison with those of effective herbicides, which have been used as control measures for volunteer- and weedy-rice growth during transplant-based rice cultivation. The control values of herbicides against volunteer and weedy rice were estimated to be 90 or greater, while the values of LN application were estimated to be 80–90 in general. Because LN acts as a beneficial nitrogen fertilizer, application of other fertilizers may be reduced during rice cultivation. On the basis of our current knowledge, future issues are discussed.

Sesame cultivation in Japan has declined due to the delay in mechanization of cultivation, but in recent years sesame cultivation is gaining momentum again due to the increasing demand and the development of new mechanical harvesting technology. However, most research on sesame in Japan has been done in the food processing field, and knowledge on their cultivation is scarce. In this review, the key points for stable and high-yielding sesame cultivation are discussed and speculated based on the summary of previous studies. The results indicated that avoiding waterlogging at the early-vegetative stage and high solar radiation in the mid-flowering period were important for high yield, and the development of low-temperature seeding technology would ensure a stable amount of solar radiation during this time. The dense planting around 20,000 plants/10 a was considered to be superior to the Japanese practice. It was also considered important to determine the optimum amount of fertilizer, using N: 4–8 kg/10 a, P₂O₅: 6–10 kg/10 a, and K₂O: 2–3 kg/10 a as a guide, and to apply fertilizer containing sulfur. The economic damage from weeds and pests should be assessed and prioritized for control, and the number of pesticides that can be applied should be expanded. It was also considered important to improve the growth at a low temperature, lodging resistance, waterlogging resistance and disease resistance by breeding.

To elucidate the effect of seedling density on the growth and yield components of direct-seeded rice on well-drained paddy fields, we conducted a three-year field experiment using high-yielding rice cultivars “Minachikara” and “Hokuriku 193”. Plots sparsely seeded (17 seedlings m^-2) and moderately seeded (33 seedlings m^-2) were set by thinning seedlings artificially, to compare plant growth with densely seeded plots (43–169 seedlings m^-2) which was the original seedling establishment by the conventional method. The sparsely seeded plot had fewer tillers per unit area, and heading date was later than in the densely seeded plot. At the vegetative stage, the average single tiller weight did not differ with the seedling density, but after heading, it was significantly heavier in the sparsely seeded plot than in the densely seeded plot. The number of panicles per unit area decreased with decreasing density, while the number of spikelets per panicle increased with decreasing density. The grain yield per unit area in the sparsely seeded plot slightly decreased or was the same as that in the densely seeded plot. However, we obtained over 900 gm^-2 grain yield in the sparsely seeded plot with “Hokuriku 193” in 2018. The yield was the same in the densely seeded plot even though the number of seedlings was only one-tenth of that in the densely seeded plot. In conclusion, lower density of seedlings induced plant growth to give a higher panicle-weight type. Therefore, the seedling density was considered an important factor in the growth control of direct-seeded rice.

Rice yield in Fukuoka prefecture, which is a warmer region, was compared with that in Akita prefecture, which is a colder region in Japan, using the main varieties “Hinohikari” and “Akitakomachi” used in these regions, respectively. Although days from transplanting to heading in“Hinohikari” in the warmer region were shorter than in “Akitakomachi” in the colder region, the mean solar radiation and mean temperature from 30 days before heading to 30 days after heading was higher in “Hinohikari” than in “Akitakomachi”. The length of leaf blade was longer and the top dry weight and leaf area at the full heading stage were larger in “Hinohikari” than in “Akitakomachi”. The total spikelet number per area was not different between the two varieties, but the percentage of ripened grain was lower in “Hinohikari” than in “Akitakomachi”. As a result, the yield was lower in “Hinohikari” than in “Akitakomachi”. On the other hand, in the statistical survey on crops, the yield was lower in Fukuoka prefecture, than in Akita prefecture, since both the total spikelet number per area and the percentage of ripened grain was lower in the former. These results suggest that the higher temperature before heading restricts the total spikelet number per area and/or the higher temperature after heading reduces the ability of ripening, resulting in the lower yield in Fukuoka prefecture, which has a warmer climate.

Twenty-four treatments consisting of combinations of four nitrogen application levels and six rice (Oryza sativa L.) cultivars with high yield and/or high eating quality were examined. The accuracy was evaluated for the estimation of growth traits (leaf area index (LAI), number of tillers, dry weight, nitrogen content of leaf and nitrogen content of plant) by nondestructive sensing data (vegetation cover rate, normalized difference vegetation index (NDVI) and light interception rate). The relationships and estimation accuracy based on data set obtained at 24, 38, 54, 66 days after transplanting (DAT) were evaluated. The coefficient of determination (R²) of regression equation between vegetation cover rate and LAI, dry weight and nitrogen content of plant, NDVI and LAI, nitrogen content of leaf and nitrogen content of plant, light interception rate and dry weight were more than 0.8 from 24 DAT to 54 and/or 66 DAT (panicle initiation stage (PI)). In addition, the R² of regression equation between vegetation cover rate of handheld camera and dry weight and nitrogen content of plant at 24 DAT, and all nondestructive sensing data and growth traits except number of tillers at 24 and 38 DAT were more than 0.7. At PI, the R² of regression equation between NDVI of handheld sensor and growth traits except dry weight, and light interception rate and LAI were also more than 0.7. It was suggested that root mean square error (RMSE) tended to be large, while there were relationships between these nondestructive sensing data and growth traits.

Although rice direct seeding cultivation is increasing in warm regions, the practice area is still small, few fertilizers are suitable for direct seeding, and fertilizers for transplantation must be applied. However, direct seeding tends to cause lodging by overgrowth due to vigorous tillers, and the reduction in the seeding amount practiced to avoid the lodging sometimes results in insufficient number of seedlings. Accordingly, it is necessary to practice cultivation without reducing the seeding amount as well as reducing the amount of basal fertilizer to suppress overgrowth. It is not realistic to distribute the fertilizer for direct seeding and it is troublesome for farmers to prepare the fertilizer by mixing. Therefore, in the rice-barley double-cropped paddy fields, we conducted rice direct seeding cultivation using only delayed-release coated urea fertilizer, the amount of nitrogen of which was 80% of that used in the conventional transplantation, and did not apply phosphorus, potassium or basal nitrogen. The study was conducted in 3 districts including the paddy fields of the farmers in comparison with the plots where the conventional fertilizer for transplantation was applied. As a result, there were no significant differences in growth or yield between the two cultivation methods. Therefore, the fertilization method using only delayed-release coated urea fertilizer could be applicable for wet direct seeding in rice-barley double-cropped fields. This fertilizer application can save fertilizer cost and labor because the amount applied is small.

Cultivar variances in the stay green trait of flag leaves in NIAS World (WRC), Japanese (JRC) rice core collection and Chinese high yielding hybrid and inbred cultivars were investigated. A leaf color reading (SPAD) was determined using the chlorophyll meter at the center of the flag leaf segment floated on water at 35°C under dark conditions for one week. There was a large cultivar variance in a ratio of after (SPAD_E) to before (SPAD_S) incubation in SPAD (GM= SPAD_E/SPAD_S). In WRC and JRC cultivars, GM in japonica rice tended to occupy a higher rate than indica and tropical japonica rice. There were typical cultivars of high GM in which both SPAD_E and SPAD_S were significantly high. In Chinese high yielding rice (9–11 t ha^-1), the GM diversely differed and positively related with harvest index and the grain yield per total straw weight × SPAD value. These relationships suggested that higher GM increased the productivity of straw for the grain yield due to maintenance of chlorophyll function. It was suggested that the stay green trait is widely distributed in rice resources and it can be used for the improvement of rice production.

The purple leaf and yellow leaf rice cultivars are recently gathering attention in order to make rice field arts or dry flowers at many districts in Japan. Rice field art is a huge artwork of figures or letters drawn in the rice field by planting rice cultivars that have leaf color mutation or colored panicles. We surveyed the agronomic characteristics of nine purple leaf and two yellow leaf rice cultivars and the effects of light on the leaf color under three kinds of covering materials (UV-cut film, black cloth and transparent film). The leaf colors were evaluated by a color-difference meter and anthocyanin contents. The nine purple leaf rice cultivars showed a large variation in heading date, culm length and leaf anthocyanin contents. The contents differed more than 10-fold among the cultivars and the hue changed from red to greenish with the change in content. The leaf hue became greenish under shading especially with UV-cut film; therefore, ultra-violet proved to be necessary for anthocyanin production. The yellow leaf cultivars contained no anthocyanin. The leaf hue of yellow leaf rice cultivar became greenish under shading especially with a black cloth (50% cut of sunlight). Furthermore, the rice leaf colors among five cultivars were evaluated using a color-difference meter, an anthocyanin meter and a green meter (SPAD), and the difference of leaf colors was clearly shown.

In barley for food uses, endosperm glassy grain rate is an important factor that affects pearling quality, while β-glucan has received increasing attention as a functional ingredient. We analyzed the factors affecting endosperm glassy grain rate and kernel β-glucan content from data collected in local growers’ fields and studied nutrient-based techniques to manage these two parameters at the Tochigi Prefectural Agricultural Experiment Station. First, we conducted factorial analysis using the cultivar Shunrai grown in farmers’ fields in Tochigi prefecture. Given that glassy grain rate and β-glucan content are strongly correlated with kernel protein content, we considered that high product quality depended on the management of protein content. Although the glassy grain rate varied with the year, the acceptable glassy grain rate level of not more than 50% was likely to be achieved when protein content was not more than 8%, with the resulting β-glucan content being 4.4%. However, our attempt to reduce protein content by low-nutrient cultivation resulted in substantial yield fluctuations and led us to conclude that this method is not suitable for achieving low glassy grain rate because it is accompanied by yield instability. Trials at the Tochigi Prefectural Agricultural Experiment Station indicated that split application at the beginning of stem elongation and 30 days before had a practical value as a fertilizing schedule because this schedule produced higher yields with lower glassy grain rate than single basal fertilization, albeit with lower β-glucan content. The results also suggested that the advisability of topdressing in light of keeping protein content within the target range could be determined by multiplying the number of stems by SPAD value, both measured 30 days before stem elongation began. The topdressing at 10 days after heading, which is believed to increase β-glucan content, reduced grain quality by increasing glassy grain rate and was therefore was considered unsuitable for Shunrai.

The objectives of this study were to evaluate the optimum planting pattern of valley-type quinoa (Chenopodium quinoa Willd.) variety, Amarilla de Marangani and the relationship between dry matter production and seed yield. Field experiments were carried out in the experimental field at Nihon University in 2014, 2016 and 2017. In all years, the planting density was 100 plants m^-2, and the intrarow width was from 6.67 cm (row width 15 cm) to 1.67 cm (row width 60 cm). The sowing time was September 3, 2014, August 31, 2016, and August 30, 2017. The seed yield was from 79.7 g m^-2 to 273.2 g m^-2. There were no significant differences in the seed yield among plots. The seed yield of this experiment was lower than that of the quinoa variety, NL-6 sown in March or April. One reason for this was the difference in the amount of solar radiation in the growing period. Seed yield and seed number were significantly correlated with the top dry weight at the flowering stage (seed yield r=0.746*, seed number r=0.756*). Thus, vigorous growth of the top until the flowering stage was needed to obtain higher seed yield of Amarilla de Marangani.

To monitor the effect of additional fertilizer application, we measured leaf area expansion in farmer’s paddy fields using multispectral images (MS images) collected using unmanned aerial vehicles (UAV). Leaf area index (LAI) growth rate (LGR), which is defined as the slope of linear regression for time-series LAI, was used for evaluation. The image analysis, which considered fluctuations of solar radiation conditions, was applied to obtain LAI from images, and compared with LAI measured by LAI-2200. Three levels of ammonium sulfate (0, 10, 15 g m^-2) were set as additional fertilizer treatments in 4 transplanted fields (2 Hitomebore, 2 Manamusume and 1 Datemasayume) and 4 direct seeded fields(Hitomebore)of a juridical agricultural union in Sendai (total 72 test plots, the area of which was 3 x 3 m). The additional fertilizer increased the number of panicles. However, there were no significant effects on the yield components. Both LAI-2200-based and MS-image-based LGRs at the center of the plot revealed significant effects only for the transplanted Hitomebore. However, significant effects were detected in both transplanted and direct seeded test plots in LGRs between the center and outside area (2 m from center) based on MS images. These results imply that the MS image by UAV can be used to monitor the effects of the fertilizer applied. The method will be useful to determine the optimal amount of fertilizer for each field by optimizing LAI growth.