For achieving high yield and grain quality under low nitrogen conditions in rice cultivation, dry matter production, yield and grain quality of the hybrid variety Hybrid Togo 3 (known for its superior palatability), the indica-type variety Oonari, and the Japanese-type variety Nipponbare were compared under high- and low-nitrogen (N) conditions in 2023 and under early- and late-type N applications of low-N conditions in 2024. Varieties that showed high yield under high-N conditions also showed high yield under low-N conditions. Although total dry matter weight did not differ among varieties, panicle weight was significantly heavier in Oonari and Tougou 3 than in Nipponbare at 20 and 40 days after heading. Rough brown rice yield was in the order of Oonari ≥ Togo 3 > Nipponbare. However, Oonari produced a considerable amount of immature brown rice. As a result, the brown rice yield was in the order of Togo 3 ≥ Oonari > Nipponbare. The proportion of perfect grains was significantly higher in Togo 3 than in Oonari. Under low-N conditions, the brown rice yield was slightly higher and the proportion of perfect was significantly higher under the late-type than the early-type N application. These results suggest that hybrid Togo 3 is optimal and the late-type N application is promising for obtaining both high yield and grain quality under low-N conditions.

For establishing a large-scale paddy field crop rotation system with reduced chemical fertilizers, soybean with which nitrogen chemical fertilizers can be reduced and corn which can be cultivated in a labor-saving manner were cultivated in the same field. Then the effects of chicken manure application on the growth, yield and soil chemistry were investigated. In soybean cultivation, nitrate nitrogen in the soil at the early growth stage was higher and the amount of root nodules was lower with the chicken manure treatment than with the chemical fertilizer or without fertilizer. In corn cultivation, the nitrate nitrogen in the soil at the early growth stage and the nitrogen absorbed during the silking stage were slightly higher in the chicken manure treatment than with the chemical fertilizer. These fertilization treatments, however, had almost no effect on the yields of soybean and corn. These results show that chicken manure or no fertilizer in the soybean cultivation and chicken manure in the corn cultivation can maintain the same yield as the chemical fertilizer. Judging from the chemical components in the soil loaded from fertilizer and unloaded into grain, N, P₂O₅, and K₂O were estimated to decrease without fertilizer in soybean and increase largely with the chicken manure treatment in corn. This suggests that the combination of these cultivation methods is suitable for a paddy field rotation system with reduced chemical fertilizers.

Abstract: To establish a cropping method for high and stable quality of bread wheat (Triticum aestivum L.) in paddy field, we investigated the effects of the preceding crop and nitrogen fertilization method on the yield and bread-making traits in bread wheat cultivar ‘Yumekaori’. The wheat grown in fields following soybean had higher yield, higher grain protein content, higher sodium dodecyl sulfate (SDS)-sedimentation volume, and better bread-making quality than the wheat grown in the fields following rice. Nitrogen topdressing at the flowering stage increased grain protein content and SDS-sedimentation volume, in both the wheat grown in the fields following soybean and rice. The relationship between grain protein content and SDS-sedimentation volume was not different between the wheat grown in the fields following soybean and rice, suggesting that bread-making quality improved to the same extent when grain protein content was increased by topdressing, regardless of the preceding crops. In addition, the wheat grown in the fields following soybean did not improve the bulk density and the grain ash content compared with the wheat grown in the fields following rice. Furthermore, in the wheat grown in the fields following soybean, the grain ash content increased by lodging due to the long culm, and the grain protein content increased above the appropriate value for bread wheat in the condition of high nitrogen fertilization. It is considered necessary to reduce the amount of nitrogen fertilizer to prevent lodging and control the grain protein content in the bread wheat fields following soybean.

The need for labor-saving and cost-reducing techniques has been increasing in rice production. High-density sowing reduces the number of nursery boxes required, and application of basal fertilizer directly to nursery boxes enables a 10–40% reduction in fertilizer use compared with conventional field fertilization. Although the combination of these techniques may enhance labor and cost efficiency, the seedling growth and grain yield have not been fully investigated. We evaluated a combination of two techniques for seedling growth, yield, and quality. The plots were divided into three groups using the sample fertilizer (Naebako-Makase, N400-100): high-density seedling plots with 20% less fertilizer (HD20 group), high-density seedling plots with 40% less fertilizer (HD40 group), and high-density seedling plots without fertilizer in the nursery box due to conventional fertilizer in the field (HDC group). The quality of seedlings grown in the HD20 and HD40 groups was still within the acceptable range for transplanting. Between the different fertilizer reduction rates, the yield in the HD20 group was 3–71 g m^-2 larger than that in the HD40 group, whereas both protein content and amylose content were 0.1–0.3 points and 0.1–0.4 points lower in the HD40 group. From the above results, the combination of the two techniques produced healthy seedlings, and the yield was better in the HD20 group, whereas the brown rice ingredient quality was better in the HD40 group.

The cracked rice kernel is a phenomenon in which cracks appear in the endosperm of brown rice. and when they occur frequently, they have a significant impact on the quality of agricultural products, including a decrease in inspection grade and eating quality. This phenomenon has been observed in many areas in recent years, and although countermeasures are urgently needed, the causes of the cracking have not been fully elucidated. Therefore, this study aimed to investigate the occurrence of cracked grains under various weather conditions by setting multiple cropping seasons and to clarify the weather factors associated with cracking. The relationship between post-heading temperature and cracking was examined by comparing the average of daily maximum temperature during 15 days after heading and the percentages of slightly-cracked grains at the accumulated temperature of 800ºC・d and 900ºC・d after heading. The results suggested that high post-heading temperatures cause slightly-cracked grains to appear before full ripening. Heavily-cracked grains tended to occur more frequently when rice moisture content was less than 22%. At a moisture content of 22% or less, there was a high correlation between the percentage of total and heavily cracked grains and maximum daily transpiration forcing (FTP); cracked grains tended to occur more frequently when maximum FTP exceeded 40.

Groundnut (Arachis hypogaea) grown without fertilizer was grown in rotation with autumn-sown and spring-sown buckwheat (Fagopyrum esulentum) for 4 years. Groundnut harvest residues were incorporated to the soil, and then cow dung pellet compost was supplied by either full width application (FA) at 1 kg/m² or stripe application (SA) at 0.5 kg/m² in planting rows, before the buckwheat crop was sown. The growth and grain yields of buckwheat grown in the FA and SA plots and the plot with a standard amount of inorganic fertilizer (IF) were compared. The growth and yield of groundnuts tended to be larger in both compost plots than in the IF plot over the 4 years. The compost released more N and P per kilogram than IF. As a result, the growth and grain yield of the autumn-sown buckwheat in both compost plots were the same as those in the IF plot over the 4 years. The spring-sown buckwheat received an application of half the IF quantity in the FA plot and one-third of it in the SA plot. The growth and grain yield of the spring-sown buckwheat in both compost plots were similar to those in the IF plot. Continuous application of compost in the field experiment improved the fertility over time. The amount of available N at sowing was significantly greater in the FA and SA plots than in the IF plot, and the inorganic N content remained consistently higher in the FA and SA plots until harvest.

The agroforestry system (AF) is an agricultural system in which crops are cultivated, or livestock are raised among trees and is said to provide various advantages including improved land use efficiency and/or soil fertility. However, very few examples and research have been reported in Japan. In this study, we conducted a 2.5-year trial of AF in combination with olive and durum wheat to examine the effects of AF introduction on the growth of both crops and soil nitrogen and carbon content. Durum wheat yield was 129 to 268 g m^-2 in the 2021/22 crop season. Olive tree height and width remained similar regardless of the introduction of AF. Soil total nitrogen content, available nitrogen content, and organic carbon content did not increase after introducing AF for 2.5 years, irrespective of the soil depth. These results revealed that the main advantage of short-term introduction of AF in Japan is the improvement of land use efficiency due to harvesting crops between trees without affecting the fruit trees. On the other hand, this study also showed some issues in olive groves with AF, such as an increased risk of damage to crops by animals and weeds. Although soil nitrogen and carbon did not increase with the short-term introduction of AF, some items showed a tendency to improve. These results suggest the need for continued verification of AF in Japan.

The effects of late-stage intensive nitrogen fertilization (LSINF) on growth, yield, and grain protein content (GPC) of Japanese wheat cultivar ‘Fukuhonoka’ were investigated in Okayama Prefecture, Japan. Our results showed that LSINF at the jointing stage (i.e., GS31) with the same total nitrogen fertilizer amount as the conventional fertilization resulted in up to 10% increase in yield compared to the conventional fertilization. Although GPC on the LSINF was higher than that of the conventional fertilization, it did not reach the standard value of 9.7% or higher for Japanese noodles. Therefore, we applied additional nitrogen at the flag leaf extraction stage (i.e., GS38). The spike number, aerial part weight, and harvest index increased depending on the amount of additional nitrogen applied. The additional application of nitrogen at GS38 maintained SPAD value of the uppermost expanded leaf at a high level during a month after heading time. As a result, the grain yield further increased as compared with that without additional nitrogen application. Additional nitrogen application also resulted in the grain protein content of the standard value of 9.7% or higher. Intensive nitrogen fertilization at GS31 and GS38 resulted in high yield and appropriate GPC of ‘Fukuhonoka’ in Okayama Prefecture, Japan.

In order to “visualize” the impact of cultivation management on yield and quality in large-scale rice farming management entities that use various cultivars over a wide range of cropping seasons, we created a Web application using the “shiny” package of R language to create graphs from comprehensively collected field-specific datasets. As farming data, we used a dataset with 1149 fields from 2019 to 2024, obtained from an agricultural production corporation in southern Ibaraki Prefecture. When users of this application choose the “productivity indices” to display yield or unmatured grain weight ratio, along with year and cultivar, graphs are drawn from the filtered data in real time. Types of graphs displayed are 1) hierarchical distribution map of “productivity indices” and scatter diagram between 2) harvest date or 3) total nitrogen fertilization amount and “productivity index”, and cultivars and field location blocks are distinguished by color filling and symbol shapes. Through the “visualization”, the users should be able to understand the effects of the collected cultivation management data on “productivity indices” more easily and become more aware of problems. When this application is used by a small number of specific users, such as planners in a management entity, it is easiest to copy the source code of the application and the data file to the designated folder on a computer with the R language installed and run it.

An average temperature during the ripening period below 23.6ºC is appropriate for improving brown rice quality of brewer’s rice cultivar ‘Ginnoyume’ in Kochi prefecture. In this study, we estimated the transplanting time to meet this criterion in each production area. Using a model for estimating heading stages and the agro-meteorological grid square data, we calculated the first transplanting date that meets this criterion in a normal year (early limit) and found that the current transplanting date in 8 areas was earlier than the early limit. Also, we calculated the last transplanting date before the first day when the daily mean temperature was 15ºC or lower (late limit) and found no areas where the early limit was later than the late limit. Furthermore, the estimated ratios of yield and protein content at the early limit to the current transplanting date in each area were 93-108% and 102-111%, respectively. However, the ratio of production value was 98-128%, and only one area exceeded the 7.3% protein content target.

These results enabled us to estimate in which areas and for how long the transplanting time should be delayed to improve the brown rice quality of ‘Ginnoyume’. In areas where the transplanting time was delayed appropriately, poor ripening due to low temperatures could be avoided, and such a delay had little impact on production value or protein content.

To verify the effect of slow-release nitrogen using organic fertilizers such as green manure, I investigated the weight of the stem, leaf and grain and their nitrogen contents in the plot with only urea (LP0), the plot with half urea plus half slow-release nitrogen fertilizer (LP1/2), and the plot with only slow-release nitrogen fertilizer (LP1). The stem, leaf and grain weights were greatest in LP0 at 23 days after sowing. At 68 days after sowing (at harvest), the growth was more vigorous in LP1/2 and LP1 than in LP0; the difference in growth was significant in LP1/2. At harvest, leaf SPAD values were significantly higher in LP1/2 and LP1 than in LP0, suggesting that the slow-release N fertilizer maintained a larger photosynthetic capacity until harvest. In LP1/2 and LP1, where the effect of the nitrogen fertilizer lasted until harvest, the grain weight and the nitrogen content of husked grains were higher than in LP0. This was considered to be the result of a combination of factors: the number of lateral branches and the number of flower clusters were large, and the seed-set percentage was high, which resulted in a large number of seeds per cluster. In addition, not only was the thousand-grain weight larger, but the husking ratio was also significantly higher.

To determine the effect of trace elements on kidney bean yield, fertilizer application containing boron and zinc (Experiment 1) was conducted at two sites, Ebetsu, a fine-grained Haplic Pseudogley soil, and Obihiro, a light Allophanic Andosols. Soluble zinc was below the lower limit of the soil diagnostic standard at both sites. The average yield increase for the FTE (fugitive boron), Agri-Ace (fugitive boron and zinc), and water soluble (water soluble boron and zinc) treatments was 12, 9, and 14%, respectively, The absence of differences in seed yield with and without zinc in the materials only for boron suggested that the seed yield increase was due to the increased absorption of boron. Five levels of boron application were

tested in Ebetsu and Obihiro (Experiment 2), including no-treatment. Seed yield peaked at 720 g/10 a of boron, and decreased at levels higher than 1080 g/10 a. In both test sites, seed yield increased at 720 g/10 a of boron and decreased at levels higher than 1080 g/10 a of boron. In Ebetsu and Obihiro, the boron content after harvest exceeded the upper limit of 1.3 ppm for soil diagnosis in the 1080 g/10 a and 1440 g/10 a treatments, respectively. The application of boron at 360 to 720 g/10 a was effective for increasing seed yield, through two experiments. and this amount of boron was not enough to accumulate enough to cause excessive damage.