To evaluate whether phosphite fertilization contributes to enhancement of soybean yield, we investigated the effects of phosphite fertilizer on yield, yield components, growth, and dry matter production of soybean (cv. ‘Oosuzu’). In 2021, to assess the effects of application concentration, we established 100× and 500× plots, in which phosphite fertilizer was sprayed at 100- and 500-fold dilutions, respectively. In 2022 and 2023, to assess the effects of the timing of application, we established early and late plots, in which phosphite fertilizer was applied at the R1 (beginning of flowering) and R5 (beginning of seeding) stages. In 2021, we detected an increase in total grain weight in response to the application of a 100-fold dilution of phosphite fertilizer, and in 2023, we found that the winnowed grain weight increased in both the early (R1) and late (R5) fertilized plots and total grain weight in the late (R5) fertilized plot. These findings revealed that the foliar application of phosphite fertilizer promotes the yield of soybean. This increase in yield can be attributed to an increase in the number of pods, whereas we observed no significant effects of phosphite fertilization on aboveground dry matter weight or SPAD during the growth period. It is accordingly suggested that the application of phosphite fertilizer during the reproductive growth period from R1 to R5 contributes to enhancement in the sink capacity, rather than source capacity, of soybeans, thereby leading to an increase in the number of pods, and hence an increase in yield.

Variable rate nitrogen application is considered to achieve a high yield and/or grain quality in wheat. In this study, we examined whether variable rate nitrogen application at the flag leaf appearing stage (GS37) increases grain protein content, which is important for the quality evaluation of wheat. In addition, we tested the availability of growth diagnostic index calculated from canopy images at GS37 as an inexpensive growth diagnostic method. Grain protein content was significantly increased 0.15 to 2.3% by application of 5 g m^-2 nitrogen at GS37. The increase in grain protein content was due to the increase in grain nitrogen accumulation by about 2 g m^-2 by supplemental application of 5 g m^-2 nitrogen. The growth diagnostic index calculated from canopy images was significantly correlated with nitrogen accumulation above ground at GS37, and six indexes showed the same slope and intercept in two cropping seasons. In the third season, we conducted a verification test to evaluate the effect of variable rate nitrogen application at GS37 in achieving high stabilization of grain protein content, based on the growth diagnostic index. Yields varied in the range of 180 to 509 g m^-2, but grain protein content was similar, ranging from 11.6 to 11.8%. Variable rate nitrogen application at GS37 based on the growth diagnostic index calculated from canopy images was considered to be an effective cultivation method for achieving high stabilization of grain quality in wheat cultivar ‘Sanukinoyume2009’.

For maintaining soil fertility and stabilizing crop production in upland fields converted from paddy fields, We conducted a field experiment using a soybean-wheat rotation system including the treatments of compost and fallow for three years. The compost treatment increased hot water extractable nitrogen, available phosphate and exchangeable potassium in the soil. However, the dry matter production and yield of soybean and wheat were not significantly affected by the compost treatment. In the second and third years of soybean cultivation, the previous wheat crop hardly affected the dry matter production and yield of soybean, although the nitrate nitrogen in the soil at the sowing time was lower and root nodule weight was larger after wheat cultivation than after fallowing. In the first and third year of wheat cultivation, the previous soybean crop hardly affected the dry matter production and yield, although soil nitrate nitrogen, leaf color during ripening and grain protein were reduced after soybean cultivation in the third year of wheat cultivation. Estimations from fertilization, nitrogen fixation and grain protein showed that total nitrogen in the soil increased by compost and decreased without applying compost. However, actual measurements of soil showed that total nitrogen increased by application of compost and did not change by not applying compost. In conclusion, the previous crop and compost had little effect on crop yield, but the application of compost changed the soil chemical properties.

We conducted a transplanting time experiment to improve the inspection grade and enzymatic digestibility of steamed rice of brewer’s rice cultivar ‘Ginnoyume’ in Kochi prefecture. We examined the relationship between inspection grade, enzymatic digestibility of steamed rice, and temperature during the ripening period, as well as changes in yield and protein content of brown rice in ‘Ginnoyume’ transplanted in mid-May, early June, mid-June, and late June in 2016, using five transplanting times in 2017 and 2018, including mid-July. In ‘Ginnoyume’, a lower average temperature during the ripening period due to later transplanting time improved the inspection grade by increasing 1000-grain weight, the percentage of whole grains, white-core grains, and by decreasing the percentage of white immature grains such as white-back grains, and also improves the enzymatic digestibility of steamed rice by changing the starch characteristics. Furthermore, the regression relationships between inspection grade, enzymatic digestibility of steamed rice, and average temperature during the ripening period, indicated that the average temperature during the ripening period to obtain first grade rice and high enzymatic digestibility of steamed rice was less than 23.6ºC. However, since later transplanting time also resulted in yield reduction and increased protein content of brown rice, it is necessary to consider appropriate cultivation methods to mitigate these negative effects.

The objective of this study is to clarify the relationship between wheat varieties and bread taste. Bread was produced by the no-time method using three flour products from the Hokkaido wheat varieties ‘Yumechikara’, ‘Haruyokoi’ and ‘Kitanokaori’, and a commercial strong flour product, ‘Kameriya’. The taste of the bread was evaluated by measuring the contents of various sugars, amino acids, organic acid and phosphoric acid of each crumb, by a sensory testing and a taste sensing system. The results revealed that the taste quality of the bread varied depending on the variety and flour product. ‘Yumechikara’ was the most similar to ‘Kameriya’ among the three varieties, with little bias in umami and sweetness. ‘Haruyokoi’ tended to be characterized by high free amino acid content and umami, but there was a large variation among the products. ‘Kitanokaori’ had a high maltose content in the crumb, which made the crumb sweet. The results of the component analysis and taste sensing system were not always consistent with that of sensory testing, indicating that each analysis method has its advantages and disadvantages. However, the taste sensing system was able to quantify the differences in bread taste, and when combined with sensory testing and component analysis, it enables more accurate evaluation of taste qualities.

To stabilize seedling emergence in direct seeding of rice in dry paddy fields, we conducted simultaneous deep seeding tests by seeding rice, wheat, soybean and corn using a seeder for upland crops. The target sowing depth was 3 cm in standard seeding and 7 cm in deep seeding. Compared with the other three crops, the number of days to emergence was longer and the emergence rate was lower at both sowing depth in rice, particularly extremely low at deep seeding. In deep seeded plants, although the first internode of wheat elongated to 3.9 cm, the hypocotyl of soybean elongated to 2.9 cm longer than in standard seeding, and the mesocotyl of corn elongated to 5.0 cm, the total length of the mesocotyl and second internode of rice was only 2.3 cm. Thus, deep seeding did not promote stem elongation in rice compared with the other three crops, which was related to the low emergence rate of deep seeded rice. Deep seeding should be avoided when conducting direct seeding of rice in dry paddy fields.

In cold regions, the duration between snow melting and sowing is short, which limits the scale of direct sowing on well-drained paddy fields. Here, we compared the growth and yield characteristics of rice directly sown in well-drained paddy fields in early winter before snow with those directly sown during the normal season (spring sowing). Although rice sown during early winter had a significantly lower seedling establishment rate and seedling number, they had earlier emergence date and higher plant height. Sampling in early July showed that rice sown in early winter had more vigorous growth than rice sown in spring; however, there was no significant difference in growth characteristics between the two groups in late July. Additionally, the heading and maturity dates of rice sown during early winter were 7 and 15 d earlier, respectively, than those of rice sown during spring. Moreover, there was no clear difference in yield and quality between early winter sowing and spring sowing. These results showed that direct seeding in well-drained paddy fields in early winter could be an effective method to increase rice yield in cold regions, and that an effective fertilization system in late July that takes advantage of the vigorous rice growth during this period may help increase yield.

Cultivation of paddy rice by applying the whole fertilizer as basal dressing in the nursery box and planting sparsely is a low cost and labor-saving cultivation technique. The number of nursery boxes per unit area can be reduced by sparse planting, but the amount of fertilizer per nursery box must be increased when combined with application of whole fertilizer as basal dressing. With the increase in the amount of fertilizer in the nursery box, there is concern about the influence on the growth and yield. This study was conducted using “Asahi-no-yume” in Tatebayashi city, Gunma prefecture. The fertilizer was “Naebako-makase” (NK301-100). The plant density in the paddy field was 11.1, 18.1, 24.2 hill/m² in the sparse, medium and dense plots, respectively. We decided the amount of fertilizer per nursery box from the amount of nursery boxes in the paddy field and the percentage of fertilizer to reduce. In 2010 and 2011, to reduce the fertilizer 50%, we applied to the sparse, medium and dense plots, 1280 g, 800 g and 580 g fertilizer, respectively, and in 2012, 1400 g, 800 g and 650 g, respectively. We carried out the cultivation experiment in the paddy field for three years from 2010. In addition, we applied chemical fertilizer by spilt application in the standard plot. As a result, the sparse plot which had the most fertilizer per nursery box, gave comparable results compared with the medium (standard) plot for growth and yield, and was not considered a problem for practical use.

Sixty-three Hokkaido rice varieties, including acclimated plants were tested for chilling tolerance at the seedling stage. The results varied from over 90% to 0% from test to test. Most recently bred lines showed low survival rates after chilling acclimation. We attempted to detect quantitative trait loci (QTL) for chilling tolerance in acclimated plants using recombinant inbred lines (RILs) from the highly tolerant ‘Kitaake’ and weakly tolerant ‘Hoshinoyume’varieties. QTL with a high contribution to chromosome 9 were detected under both dark and light/dark conditions during the chilling treatment. This result indicates the possibility of using chilling tolerance in acclimated plant QTL to breed for chilling tolerance at the seedling stage.

The effects of seedling density and nitrogen application method on the characteristics of the high-yielding, good-tasting, and high-quality rice cultivar “Niji-no-kirameki” in flooded direct-sowing cultivation were examined, across cultivars and cultivation methods. Under the same nitrogen application methods in surface broadcast or hill sowing, “Niji-no-kirameki” produced higher yields than the existing cultivars “Koshihikari” and “Kinuhikari” that have similar heading periods, and had superior brown rice appearance quality. In addition, the short culm of “Niji-no-kirameki” gave it superior lodging resistance. Seedling density had almost no effect on the yield of “Niji-no-kirameki”, but the amount of nitrogen application had a large effect. There was a positive correlation between yield and the number of rough rice grains per square meter (NG), and the relationship between the direct-sowing and the transplanting was not different. However, the number of panicles required to produce the same NG was greater with direct-sowing, and the leaf color tended to remain lighter than with transplanting. In direct-sowing, the rice protein content was slightly higher when trying to obtain the same level of yield as transplanting. Therefore, in direct-sowing, the target yield of “Niji-no-kirameki” was 660 g m^-2, with 31,000 of NG, leaf color at the full heading stage with a SPAD value of approximately 34, and a brown rice protein content of 6.5% (15% moisture basis) would be appropriate.