Superior grain quality and high yield variety ‘Niji-no-kirameki’ and popular variety ‘Koshihikari’ were cultivated for 2 years under the conditions of 2 transplant times and 3 fertilization methods. Their grain qualities were compared from the viewpoints of the growth and cross-sectional traits of grain according to different positions within the panicle.‘Niji-no-kirameki’ was superior in grain quality to ‘Koshihikari’ under all cultivation conditions: clearly fewer white-back grains in the inferior position under a high temperature, fewer ventral white and white core grains in the superior position, fewer core white grains by rachis-branch removal and fewer milky white grains by leaf removal. These results indicate that the quality of‘Niji-no-kirameki’ decreases less under high temperature conditions and under the conditions of excess or shortage of assimilates. This might be due to the slow growth of grain at every position within the panicle in ‘Niji-no-kirameki’. On the other hand, the causal relationship between the cross-sectional traits of grain and grain qualities was unclear, although the dorsal-ventral ratio of grain became lower under a high temperature. From these results and our previous reports, the long ripening period is considered to be a factor contributing to the high yield and superior grain quality in ‘Niji-no-kirameki’.

Variable-rate nitrogen (N) application effectively stabilizes high wheat yields, but few studies have examined the effects of the timing and amount on N application on the yield and spike number. In this study, we tested whether variable-rate N application at the emergence (GS11) and/or fourth leaf appearing stage (GS14) would enhance stem number, ear number and yield in a canopy. In the plots with only half the standard number of seeds sown (half-sown), the number of stems in GS11 was about half of that in the standard plot. The maximum number of tillers in the half-sown plots was similar irrespective of N application at GS11. In the 2021/22 season, the number of maximum tillers was about 350 m^-2 irrespective of the N applied at GS14. The reason for the lack of increase in the number of tillers was that the increase of N content at the initiation of the stem elongation stage (GS30) was less than 6% of the applied N. Yield in 2021/22 was 445 g m^-2, similar to the standard sowing plot, irrespective of N application at GS11 and/or GS14. Yield in 2022/23 was 38 to 48 g m^-2, and was significantly lower with increasing N application at GS11. The effect of N application on N content at maturity was similar to that on yield. Plots, where N was applied at GS11 and/or GS14, showed higher canopy coverage at GS30 and a severe lodging degree at maturity. When applying greater amounts of N after GS30, it was considered more important to establish a reliable number of wheat plants than with variable-rate N application at GS11 and/or GS14.

Lodging is a serious problem, because it causes yield loss and deterioration in quality. Until now, lodging resistance has been improved mainly by shortening the plant height. However, even such rice varieties have been lodging due to super strong typhoons in recent years. In this study, we compared strong culm traits related to the lodging resistance of recently bred varieties and examined the superior haplotypes for a thick culm. Furthermore, we focused on the morphology of cortical fiber tissue and cell wall components to clarify the factors that cause varietal differences in culm stiffness. There was a large varietal difference in the bending moment at breaking (M). We examined the factors separately in terms of section modulus (SM) and bending stress (BS), and found that a large SM for rice cultivars for forage use and high BS for ‘Hinohikari’, a rice variety with high eating quality, were responsible for the high lodging resistance. The relationship between haplotypes of genes related to culm thickness and SM revealed that the varieties with the largest SM had several superior haplotypes derived from indica and tropical japonica rice varieties. In addition, the comparison of ‘Hinohikari’, ‘Koshihikari’, and ‘Akidawara’ to clarify factors related to culm stiffness of ‘Hinohikari’ suggested that hemicellulose and starch density, rather than the thickness of cortical fiber tissue, contributed to the differences in BS among three varieties.

Excess soil moisture damage of wheat has a serious impact on wheat productivity in Kitakami city, in Iwate prefecture, Japan, where farmers in upland areas break furrows and unite some small fields to raise cultivation efficiency. To evaluate the effectiveness of open ditches and underdrains for wheat productivity at the field where have a risk of excess soil moisture damage, we conducted an on-site experiment. The four targeted fields were two with open ditches, one with underdrainage, and one with no treatment (control). Estimation of field yield using a yield monitoring combine harvester estimated the field yields, revealed greater than 25% higher yields with open ditches and underdrainage than that of the control field. Unattended Aerial Vehicle (UAV) images showed the wheat growth changes caused by soil moisture damage, with variations corresponding to the yields. The results showed that open ditch and underdrain systems improved the drainage and crop growth proving the benefit for crops threatened by excess soil moisture damage. The targeted fields had some gentle slopes caused by the breaking of furrows, leading to low soil fertility and depressions with insufficient drainage. The wheat planted in these fields showed poor growth by the Digital Surface Model (DSM). The yield monitoring combine harvester and UAV remote sensing provided labor-saving means for evaluating on-site experiments. Local constraints on farmer fields such as soil heterogeneity need to be removed. Further verification is required to determine the usefulness of open ditches and underdrainage for application in this and other regions.

In the Hokuriku region, yields and dry weights of high-yielding cultivars under early- and normal-planting were compared to verify whether the extreme early-planting around April 20 is possible. First, the15-day-old seedlings of indica cultivars “Hokuriku 193” and “Oonari” were confirmed to be more susceptible to low temperatures than the japonica cultivar “Akidawara”. In early-planting, the average temperatures during the first 3 days after transplanting were low and ranged from 7.8 to 17.3°C. In early-planting, the indica cultivars showed yellowing of leaves and death of lower leave immediately after transplanting, but the plant growth recovered with increasing temperature. Early-planting of all cultivars showed a longer lag from planting to start of growth than the normal-planting. However, due to the longer days to heading, there was no difference in the actual growing period until heading, which is calculated from the period from the start of growth to heading. Since the calendar day of heading was earlier in early-planting, the daily radiation during ripening tended to be higher in early-planting. As a result, the brown rice yield was not lower in any year or cultivar in early-planting. Therefore, this early planting technique may be a promising cultivation technique that can mitigate work conflicts in spring.

‘Kashimamugi’, a six-rowed barley cultivar, is prone to culm breakage after maturity. In this study, we investigated the occurrence of culm breakage after maturity of ‘Kashimamugi’, and examined the culm characteristics of ‘Kashimamugi’, and ‘Kashima Goal’ which is also a six-rowed barley and has resistance for culm breakage after maturity. The breakage after maturity occurred in the upper part and lower part of the first internode and sometimes occurred on the second internode. The culm of ‘Kashimagoal’ had a smaller section module and larger bending stress than that of ‘Kashimamugi’. The culm of ‘Kashimagoal’ had also a thicker epidermal cell layer and higher lignin content than that of ‘Kashimamugi’. The culm moisture of ‘Kashimagoal’was maintained until maturity, and the reduction of dry matter was small. The bending stress and bending moment at breaking of ‘Kashimagoal’ were maintained until maturity, which was assumed to be related to the resistance of the stem breakage after maturity.

We examined the applicability of the values of vegetative coverage ratio, obtained by a smart-phone application for diagnosing the amount of ear fertilizer applied, as one of the growth diagnostic indicators of the Sake rice variety, Yamadanishiki. Utilizing statistical methods, we compared the values of the vegetative coverage ratio (our proposing labor-saving method) with those of the growth index value (one of the traditional labor-intensive methods) on the panicle formation stage. The study was conducted in six cropping seasons during the three years from 2017 to 2019, with four levels of base fertilizer applied at different transplanting periods. The values for all investigation items were higher with the increase in fertilizer application. We found differences amongst cropping periods, except for the values of the above-ground nitrogen content. There was a positive correlation between the values of vegetative coverage ratio and those of the above-ground nitrogen content, as well as those of the growth index value. Furthermore, a positive strong correlation existed between the values of the vegetative coverage ratio and the growth index value. In summary, we conclude that the vegetative coverage ratio is an efficient and promising growth index, as an indicator for the growth diagnosis of Yamadanishiki.