Increasing the yield potential of rice (Oryza sativa) is the main objective of breeders and cultivators engaged in rice improvement programs. Erect panicle (EP) rice is generally high-yielding with panicles that remain non-curved until maturation. The aim of our study was to evaluate the association of agronomic traits with rice productivity in EP rice. Here, we used the recombinant inbred lines (RILs), crosses between Liaojing5 (erect panicle japonica type) and Wanlun422 (high-yielding indica type). The yield varied among the RILs, and the flag leaf length of EP RILs was negatively correlated with the yield; however, the correlation was not significant in the non-EP RILs. The flag leaf length of the EP RILs was also negatively correlated with biomass increase during the late ripening stage. This may reflect the canopy structure of the EP RILs with short flag leaves which had a larger leaf area index in the lower strata. Additionally, the chlorophyll content in the lower leaf significantly differed among the EP RILs with flag leaves of different lengths, resulting in a higher photosynthetic ability of the lower leaf of EP RILs with short flag leaves. In the present study, an EP line, which has the shortest flag leaf, showed a higher yield than Wanlun422 in both years. EP RILs with short flag leaves might show a higher canopy photosynthetic rate in the later ripening stage; therefore, this trait could be a potential phenotypic marker for achieving high yield of EP rice. Graphical Abstract

Previous research into the effects of ultrafine bubbles (UFB) on plant growth have been contradictory. To facilitate the resolution of these contradictions, the aim of the present study was to clarify the interspecific differences in growth responses among cereal/leguminous species under different levels of UFB concentrations. Seedlings of six species were grown hydroponically with three different UFB concentrations and two levels of plant nutrition to evaluate biomass and elongation growth. UFB growth promotion under zero-nutrition occurred in all species. Interspecific differences were noted in response to differing UFB concentration levels. Rice and soybean had higher above-ground biomass production at both low and high concentrations. Conversely, other crops exhibited promoted growth at only one of the concentrations. Negative effects occurred in full nutrient conditions except for root elongation. This study demonstrated that growth-promoting effects with UFB depended on the crop species being tested and the concentration of UFB used. Graphical abstract

Coffea arabica, an economically important crop, accounts for most of the coffee consumed globally. Increasing temperature due to climate change can cause a decrease in productivity in many crops, including coffee plants. The maximum temperature at which damage is induced has been reported for many crops, but it remains unclear in coffee plants. Here, we investigated the effect of different temperatures and the physiological damage induced by heat stress using both leaf disks and intact plants of Coffea arabica ‘Typica’. In the experiment using intact plants, we observed leaf damage by a decrease in soil plant analysis development value, and an increase in electrolyte leakage after exposure to 45°C for 96 h, whereas no leaf damage was observed for 72 h. The leaf surface temperatures after exposure to 45°C for 72 and 96 h were 44.0 and 46.3°C, respectively. Thus, a tolerance threshold in leaves of C. arabica ‘Typica’ under heat stress are likely between 44.0 and 46.3°C. The activities of catalase (CAT) and superoxide dismutase (SOD) decreased at 45°C in both leaf disks and intact plants. The decrease in the activities of SOD and CAT under heat stress may be responsible for the increased levels of reactive oxygen species, such as O₂⁻ and H₂O₂, and the resulting cellular damage. Our findings provide valuable insights into the physiological responses of Coffea arabica ‘Typica’ to heat stress, which may contribute to the breeding and screening of tolerant cultivars in the future. Graphical abstract

Erect panicle rice cultivars utilize solar energy effectively and have improved ecological growing conditions. Among such cultivars, Shennong265 has been grown successfully throughout Northern China. Nevertheless, no studies have yet examined the relationships between crop dry matter productivity, weather conditions, and nitrogen uptake of the erect panicle type rice cultivar in Japan. The objective of our study was to evaluate the productivity of erect panicle rice Shennong265 in Western Japan under varied conditions. Three rice cultivars, Shennong265, Nipponbare, and Takanari were grown in the field under different fertilizer and plant density conditions in Western Japan; using this information, we compared yield and growth characteristics of Shennong265 with those of Nipponbare and Takanari. Although Shennong265 had radiation use efficiency similar to that of the high yielding cultivar (Takanari) and much higher leaf nitrogen content than Takanari and Nipponbare, the average grain yield of Shennong265 grown under normal fertilizer and plant density conditions was approximately 6.9 t ha⁻¹ as against 6.2 t ha⁻¹ for Nipponbare and 9.6 t ha⁻¹ for Takanari. These results suggest that, while Shennong265 has a high yield potential, the environmental conditions including climate, fertilizer, and planting period provided in this study were not suitable for achieving its maximum yield. The reduced performance of Shennong265 may be caused by insufficient fertilizer after heading and by shorter growth periods, as well as by the climate of Western Japan. Additional fertilizer application during the heading stage and earlier transplanting may be needed to obtain higher Shennong265 yields in Western Japan.

With increasing annual global coffee consumption, the amount of spent coffee grounds (SCGs) increases. Direct application of SCGs in large agricultural fields can potentially improve soil and control weeds in an environmentally safe manner. However, except for composting, the use of SCGs during cropping has not been implemented thus far because of inhibitory effects on crop growth observed in pot-based studies. We evaluated the effect of a top dressing approach to direct SCG application on crop biomass, soil improvement, and weed control, through double cropping field experiments using wheat and soybean. The field experiments were conducted over six successive cropping seasons in an upland field converted from paddy, and crop and weed biomass as well as soil total carbon and nitrogen were investigated. To avoid growth inhibition, the SCGs were surface broadcasted after crop germination to mimic living mulch. The soil total carbon and nitrogen contents increased significantly under an SCG concentration of 5 kg m⁻² or more, approximately 20 months after the first application, whereas SCG application did not significantly affect crop yield except for the first cropping of wheat. In addition, the 10 kg m⁻² SCG application reduced the weed biomass by 50% or more during cropping, except for the wheat cropping in the second year. We concluded that top dressing with SCGs after crop germination is an efficient method for sustainable agricultural production, although further detailed studies of SCGs’ effect on the crop growth and soil characteristics are required. Graphical abstract

The production of pearl millet (Pennisetum glaucum (L.) R.Br.) is important in Namibia, in sub-Saharan Africa, owing to the prevailing low precipitation conditions. Most fields supporting crop production in northern Namibia are located in a network of seasonal wetlands. The aim of the present study was to evaluate the effects of ridging and fertilizer application on the yield and the growth of pearl millet in the seasonal wetlands under different rainfall conditions. The study was conducted for two years (2017–2018) in the experimental fields in northern Namibia, and yield, yield components, and growth parameters were evaluated in relation to the application of different fertilizers (manure and mineral) with and without ridge-furrows. Manure fertilizer application presented the highest yield in 2018, whereas mineral fertilizer application showed the highest yield in 2017. The proportion of rainfall was the highest during the mid-growth period in 2017, and the reproductive stage in 2018. Thus, pearl millet plants under manure fertilization overcame damage resulting from waterlogging stress during the seed setting stage by improving the soil and plant nutrient conditions. In contrast, the plants under mineral fertilization were more tolerant to large amounts of rain during the mid-growth period. In this study, yield was mainly determined by total dry weight, and it was closely related to panicle density in both years. Therefore, we concluded that fertilizer application, including additional fertilizer based on the growth diagnostic, could be important for improving crop production in seasonal wetlands.