The cultivation of buckwheat (Fagopyrum esculentum Moench) started recently on northern Okinawa Island and Miyako Island, Japan. The physicochemical properties such as soil organic matter content and phosphorus (P) form of Kunigami Merge, a red acidic soil on northern Okinawa, and Shimajiri Merge, a dark-red neutral soil in Miyako, are very different from those of Andosols (black soil) in the traditional buckwheat cultivation areas in Japan. In this study, we grew buckwheat on these soils in Okinawa, and compared the growth, yield and nutrient uptake on the red soil with those on the black soil. Growth and yield were lower on the red soil than on the black soil due to fewer flowers on the lateral branches and lower seed-set-ratio. The stem and grain N contents were low on the red soil. The stem P content was significantly higher on the red soil, although the grain P content was low. The K content in all parts was the lowest in the dark-red soil, although the stem Ca content was the highest. The Mg content in all parts was the highest in the red soil. The stem weight, grain weight, and the number of lateral branches had significant positive correlations with the soil N and Al-bound P contents, but no correlations with the soil Fe-bound P and available P contents. Low growth and yield on Okinawa soils seemed to be due to the binding of fertilized P with Fe.
Lime nitrogen (LN) suppresses the emergence of volunteer rice originating from high-yielding rice cultivars. However, the appropriate technique or environmental condition for utilizing LN remains unclear. In this study, we examined the effect of the timing of tilling after the application of LN considering the meteorological factors. In a pot experiment, rice emergence decreased as the duration from LN application to the mixing of seeds and soil increased, from 3 to 20 days under appropriate water conditions. Immediate mixing of seeds and soil after LN application did not decrease emergence, and continuous drying conditions before and after LN application rarely suppressed emergence. In field experiments, we created a pseudo rough rice dropping condition by broadcasting the seeds after removing rice straw from the paddy field. Immediate tilling after LN application did not suppress the seedling establishment of volunteer rice. Our results suggest that the duration from LN application to tilling should be at least two weeks under an average temperature of 11 to 15ºC and appropriate soil water conditions. Even in the presence of rice straw residue, the percentage of germination after wintering declined when seeds were buried in the soil for a certain period after LN application. However, the suppressive effect of LN might be less than half of that in the absence of rice straw.
Differences in the processing quality of tofu, particularly firmness (defined as breaking stress), were estimated by analyzing soybean seeds using near-infrared spectroscopy (NIRS). All NIRS measurements on soybeans grown in different years, in different sample forms (whole or pulverized seed), and types of spectra (raw or second derivative), showed a strong correlation with the measured firmness of the resulting tofu. Estimates of firmness calculated from the second derivative spectra of whole soybean seeds provided the easiest scanning process, which was most suitable for unknown samples. Because the prediction accuracy was also good for soybean seeds grown in different years, this NIRS method is not only accurate enough for practical use in screening but also has the potential for evaluating and selecting breeding lines of soybean, especially in early generations.
Spikelet sterility is increased under high temperatures at the reproductive stage in rice (Oryza sativa L.). We thus investigated whether plant hormones, such as auxin and jasmonic acid, alleviate spikelet sterility caused by high temperatures at the booting stage. Rice cultivars, Akitakomachi, and Koshihikari, were grown in pots, and the plants were exposed to 39ºC day/25ºC night for 5 successive days at the booting stage. The entire shoots were sprayed with auxin (IAA) or jasmonic acid (JA) solution before and during the high-temperature (39ºC) treatment four times in total. Plants grown at 25ºC day/25ºC night were similarly sprayed with plant hormones to serve as controls. The panicles, headed 5 to 6 days after the treatment, were sampled at maturity and the percentage of sterility was determined. The application of 10–7 M IAA alleviated spikelet sterility caused by the high temperature in Akitakomachi, while JA had little alleviation effect. In contrast, the application of neither IAA nor JA had any significant alleviation effect on spikelet sterility caused by the high temperature in Koshihikari.
Bioethanol is a promising alternative to fossil fuels and a potential countermeasure to global warming. We have been studying Erianthus, a perennial C4 grass, as a raw material for cellulosic bioethanol, mainly because it has potential of high biomass production due to its large canopy. The effect of tillering on biomass production in Erianthus has hardly been studied. Preliminary observation showed that there might be three kinds of tillers, namely dead, old and new ones in Erianthus. Old tillers with a stem apex restarted growing after overwintering. Such old tillers were slowly followed by the appearance of new ones which started to develop. Both old and new tillers were well developed in the peripheral zone of each individual, probably because there was room for the development of tiller buds. The shifting and formation of these tillers in Erianthus secures leaf number and leaf area at the growing stage, contributing to high biomass productivity.
To select standard rice cultivars for evaluating tolerance to kernel cracking, we investigated cracking tolerance at 3 breeding stations of Japan in 2015 to 2017. Based on the percentage of cracking rice determined by using the late harvesting method, we selected 13 new standard cultivars from ‘tolerant’ to ‘weak’ in early and medium heading groups in the Tohoku and Hokuriku regions and regarded‘Ouu431’, ‘Ukei1210’ and ‘Eminokizuna’ as ‘tolerant’ standard cultivar. All 13 new standard cultivars except ‘Ouu431’ and ‘Ukei1210’ could also be evaluated by the soaking method using unhulled brown rice and the moisture absorption method using brown rice harvested at the proper time as alternative methods to the late harvesting method.
We examined the practical applicability of the method of minimum tillage and concurrent seeding using a chisel plow (CPS) in a crop rotation system by comparing the seeding work hours, growth, yield, and quality obtained using CPS with that obtained using broadcast cultivation (broadcasting) on an Andosol upland field converted from a paddy field. Seeding work hours was about 10% less than that in broadcasting. The soil pulverization rate was lower in CPS than in broadcasting, but there was no significant difference in the rate of seedling establishment between them. There was no difference in the aboveground dry weight, leaf-area-index (LAI), and leaf color during the period from the flowering stage to the grain-filling stage. The relative solar radiation on the ground surface until the flowering stage was higher in CPS than in broadcasting. There was no significant difference in the number of weeds between broadcasting and CPS, but the individual dry weight of the weed tended to be heavier in CPS. No significant difference was found between broadcasting and CPS in the growth, yield, and quality. These results suggest that CPS in crop rotation systems in paddy fields is a labor-saving cultivation technique suitable for soybeans, as is broadcasting.