As a countermeasure against the depletion of fossil fuels and global warming, the use of biomass energy as a renewable energy source is attracting attention. In the cultivation and utilization of energy crops, it is essential to avoid competition with food production and to establish low-input cultivation systems. Among candidate feedstock crops, Erianthus has been recognized as a promising species. However, its cultivation and utilization have been scarcely studied. Therefore, this study aimed to establish a sustainable cultivation and utilization system by investigating the canopy structure that forms the basis of biomass production, growth, development, and morphological characteristics of individual plants within Erianthus populations. In addition, assuming practical utilization, it is necessary to evaluate an integrated system that includes not only cultivation but also biomass harvesting, drying, and utilization. Accordingly, harvesting and drying methods were also examined. Based on these findings, the business feasibility of the cultivation and utilization system was evaluated. These results may contribute to post-disaster reconstruction following the Great East Japan Earthquake and to countermeasures for abandoned farmland.
Yield loss in rice (Oryza sativa L.) caused by low temperatures during the reproductive stage results from the induction of male sterility. This can be critical for rice production in cool climates. This review summarizes the physiological and molecular mechanisms that underlie cold damage. Recent advances in genome‑analysis technology have accelerated the breeding of tolerant cultivars by identifying key genetic regions associated with mitigation of cold damage. The review concludes with future perspectives for research on how to more reliably grow rice under unpredictable future cold‑stress conditions.
Salinity is a key abiotic stress affecting about 1.2 million hectares of arable land in Bangladesh’s coastal regions impacting agriculture and food security, with figures increasing over decades (Recent report of SRDI). Here, IR58443-6B-10–3, an IRRI genotype exhibiting high salinity tolerance at both seedling and reproductive stages, was used to identify novel quantitative trait loci (QTLs) for tolerance. An F2:3 mapping population from a IR58443-6B-10–3/BRH11-9–11-4-5B cross was created, and 47 most tolerant and 47 highly sensitive lines were chosen through selective genotyping via distributional extreme analysis for phenotypic evaluation. A genetic linkage map was constructed using 183 SSR and InDel markers. A tight cluster of QTLs was detected on chromosome 1 covering QTLs for the visual phenotypic score, survival percentage, Na concentration of leaf, panicle number, panicle length, total dry matter production, sterility percentage, Na concentration of flag leaf and grain yield. Two clusters of QTLs were also found on chromosomes 11 and 12 for Na+ concentration of flag leaf and the Na/K ratio. These three chromosomal positions represent three probable candidate genes LOC_Os01g63410, LOC_Os11g44710, and LOC_Os12g29860 that perform important functions under stress. These three loci are novel and important for tolerance to salinity at both seedling and reproductive stages and could be targeted for high-resolution mapping. Earlier studies detected QTLs for salinity tolerance at two growth stages separately in different rice genotypes. However, this study is the first to demonstrate that the same genotype, IR58443-6B-10–3, harbors QTLs for resilience at both seedling and reproductive stages, enabling future QTL pyramiding.
Soybean production in converted paddy fields is frequently constrained by poor drainage and transient waterlogging. This study evaluated whether crack treatment that creates vertical cracks in the subsoil enhances soybean yield under rice-soybean close mixed-planting. A five-year field experiment was conducted with split-plot arrangements of water regime and crack treatment. Across years, crack treatment significantly increased soybean yield in both single- and mixed-planting systems under waterlogged and non-waterlogged conditions. Yield improvement was primarily associated with greater aboveground biomass and increased pod number, whereas seed number and 100-seed weight were largely unaffected. Crack treatment generally increased soybean relative yield within the close-mixed planting system, although rice relative yield generally showed neutral or negative responses. In a hot and relatively dry year, rice relative yield declined after treatment. These results indicate that integrating physical soil modification with biological facilitation can stabilize soybean production, although its effectiveness depends on post-treatment climatic conditions.
The Sudan Savanna, a major agricultural region in West Africa, faces growing food insecurity driven by population growth, soil degradation, and climate change. In this region, climate variability, crop production, nutrient dynamics, and farm-level outcomes are closely interconnected, yet research has often examined them separately. This review adopts a soil-centered research integration perspective, using soil heterogeneity as a framework to connect evidence from soil science, agronomy, crop adaptation, climate research, and farm economic analysis. It synthesizes current evidence on how variation in soil properties, including rooting depth, water-holding capacity, drainage, and nutrient availability, mediates climate change impacts on crop production, affects the performance of management practices, and shapes adaptation options for smallholder farming systems. Reviewed studies show that dominant soil types produce contrasting crop responses to drought and excess moisture, intensify genotype × environment interactions, and generate soil-specific responses to fertilization and planting density. Climate projections further suggest that rising temperatures and more frequent heavy rainfall events will intensify both drought- and moisture-related stress, increasing spatial heterogeneity in production risk. We argue that effective adaptation requires better soil information, improved characterization of soil hydrology, crop models linked with seasonal rainfall forecasts, and stronger integration of these insights into farm economic analysis that considers both expected returns and downside risks across soil – crop combinations. By placing soil at the center, this review offers an integrated framework for linking biophysical processes with farmer-oriented decision-making in climate-resilient agricultural development.
In the Tohoku region of Japan, a cold-climate area, paddy-field agriculture faces challenges due to the aging population, the decline in farming labor, and the prolonged decline in the price of rice. These factors have accelerated the adoption of labor-saving, low-cost cultivation methods, such as dry direct seeding of rice using plowing and compaction (DDSPC). DDSPC is a mechanized system that is well suited to large-scale fields and high-speed operations, and uses multipurpose farming machinery for rice and upland crops. In DDSPC, compaction primarily suppresses vertical water infiltration, thereby preventing water leakage and stabilizing crop establishment and input efficacy without forming a puddled plow sole. This makes DDSPC a promising method for rice cultivation and a core technology for developing paddy field crop rotation systems. A two-year, three-crop rotation involving rice, wheat, and soybean was first established, achieving yields comparable to conventional practices. The rotation system was subsequently expanded to include grain maize, overcoming its vulnerability to water damage through DDSPC without a plow sole. In converted paddy fields, compared to conventional rotary tillage, grain maize cultivation using plowing maintained yield while improving lodging resistance. Integrating grain maize further facilitated crop–livestock linkages through manure use to reduce chemical fertilizer inputs and feed utilization. This review synthesizes the development of DDSPC and its roles in paddy-field rotations in the Tohoku region, and discusses future directions for sustainable paddy agriculture under increasing labor constraints.
Perennial wheats produced grain for up to 4 years in southern Australia, but quantitative data are lacking on dry matter (DM) allocation above- and below-ground over regrowth cycles. This paper examines performance of 4 perennial wheats (147235a [235a], 147280b [280b], OK7211542 [OK72] and 11,955), a perennial grass (148055 [055]), and a replanted-annual bread wheat (Wedgetail) over 3 years in large soil columns. By year 3, total DM increased to 137 g pl(-1) in perennial wheat and 194 g pl(-1) in perennial grass, but remained at 55 g pl(-1) in annual wheat. In the annual wheat, a higher proportion of its root DM was in the 30-60 cm layer with none below 120 cm, while perennial wheats increased their root DM below 60 cm each year, and perennial grass had the most below 120 cm. By the third year, spike DM was 11, 39, 25, 20, 11 and 5 g pl(-1) for Wedgetail, perennial wheats 11,955, OK72, 235a, 280b, and perennial grass, though Wedgetail was bird damaged. The results demonstrated that perennial wheats could exceed annual wheat in total and especially deep root DM, and with spike DM equalling or exceeding the annual wheat by the third year. Contrary to previous reports, any reduction in performance in later cycles was associated with lower spike DM pl(-1), rather than reduced plant stand, following exposure to moderate water deficit in the previous dry season. Annuals and perennials differed in DM allocation; perennial wheat prioritised roots over shoots, until a suitable foundation was established.
Low temperature during the booting stage, particularly the young microspore stage (YMS), reduces pollen production and spikelet fertility in rice. Tolerant genotypes produce more pollen in the anther and achieve higher spikelet fertility, but the relative importance of anther morphology, pollen maturation, pollen transfer, and germination remains unclear. The objective of this study was to determine the likely causal pathways linking anther length, pollen production, pollen maturation, anther dehiscence, and pollen germination to spikelet fertility under YMS low temperature stress by comparing the results of several pathway analyses for potential deployment of these traits for improvement of low temperature tolerance. Two experiments were conducted using 22 genotypes, including recombinant inbred lines developed from low-temperature-tolerant Norin-PL8 backcrossed with Kyeema. Morphologically, pollen production in anther was a key contributor to spikelet fertility, with anther length explaining 72.4% of variation in the number of pollen in anther (beta = 0.85). Pollen germination after YMS low-temperature stress was greatly reduced, averaging 27% despite warm conditions during germination, yet tolerant genotypes maintained higher germination. Physiologically, pollen maturation quality was also found to be a key developmental checkpoint: engorged pollen (beta = 0.56) and pollen germination (beta = 0.38) each contributed significant effects, together explaining 62.7% of the variation in spikelet fertility. Tolerant genotypes, therefore, appeared to combine greater anther length and pollen production with better pollen maturation and germination capacity, suggesting that morphology, maturation, transfer, and germination operate as coordinated mechanisms of YMS low temperature tolerance.
In crop plants subjected to soil moisture stress, older leaves wilt more severely than younger leaves on the same stem. This study investigated the differential responses of older and younger leaves to water stress, as well as the underlying mechanisms, using maize grown in pots. As soil moisture decreased, turgor pressure (TP) declined more markedly in older leaves than in younger leaves, whereas osmotic potential showed almost the same decrease across all leaves. Thus, the pronounced reduction in TP in the older leaves was attributed to a substantial decrease in water potential (Psi(leaf)). Stomatal conductance also decreased more strongly in older leave, supporting the conclusion that the greater decrease in Psi(leaf) resulted from reduced water transport to these leaves. Using the rehydration kinetics method, we estimated hydraulic conductance from root to leaf (Kroot-leaf), from stem to leaf (Kstem-leaf) and within the leaf (K-leaf) in plants under water stress, and calculated hydraulic conductance in the root (K-root) and stem (K-stem). The values of K-stem and K-leaf for older leaves decreased to approximately 50% of those for younger leaves, whereas the decrease in K-root for the older leaves was only 15%. Consequently, the larger reduction of Psi(leaf) in older leaves under soil moisture stress was primarily attributed to decreases in K-stem and K-leaf. Additionally, xylem vulnerability to cavitation in the stem and leaf under water stress likely explains the observed difference in dehydration between younger and older leaves. [GRAPHICS]
Soybean roots play a crucial role in resistance to salt stress, but their responses to sequential changes in salt concentration remain unclear because of the complexity and dynamism of their responses. In this study, hydroponic experiments were conducted using three near-isogenic lines (NILs) with and without salt tolerance conferred by Ncl alleles to investigate the morphological and absorptive responses of salt-tolerant soybean roots under sequential salt conditions. The results demonstrated that under high salt concentrations, the salt-tolerant lines maintained their root dry weight and enhanced several root morphological traits, particularly the lateral root number and root surface area. In contrast, under low salt concentrations, the root dry weight tended to increase in the salt-sensitive lines. Significant interactions between salt concentration and salt tolerance were observed for root dry weight and volume, suggesting that a trade-off between root growth and salt tolerance is mediated by Ncl alleles. A correlation between taproot length and lateral root length was observed in salt-sensitive lines but was not evident in salt-tolerant lines. Although no significant difference in the xylem sap exudation rate was observed between the salt-tolerant and salt-sensitive lines in terms of osmotic water transport, the salt-tolerant lines exhibited significantly greater hydraulic resistance than the salt-sensitive lines did. This may indicate that the salt-tolerant lines increase lateral root number as the salt concentration increases. These findings provide additional insights into the responses of soybean roots under varying salt-stress conditions and contribute to a deeper understanding of the physiological and morphological mechanisms underlying salt tolerance in soybean.
Climate change and poor crop management threaten groundnut productivity in the semi-arid tropics (SATs). To address this, a field experiment was conducted at ICRISAT in Hyderabad, India, during 2016-17 and 2017-18. The study used two prevalent groundnut varieties, ICGV91114 and ICGV00351. It evaluated four paired-row (PR) systems with different planting geometries: PR1-20:20 cm/40 cm & times; 10 cm; PR2-25:25 cm/50 cm & times; 10 cm; PR3-20:20 cm/25 cm & times; 10 cm; PR4-15:15 cm/22.5 cm & times; 10 cm, along with the standard spacing PR5-30 cm & times; 10 cm. Results showed that ICGV00351 outperformed ICGV91114 in both years. Among planting geometry, pod yield, economic water productivity, and profitability were higher in PR2 than PR1. Similarly, the highest average soil moisture was recorded in PR2 i.e. 1.87-2.01 cm in the 0-30 cm soil depth in both years. This enhanced soil moisture in PR2 improved nutrient availability and uptake, resulting in higher leaf area index, biomass yield, water productivity, and net returns. Bayesian probability and bivariate plots further confirmed that PR2 was the most promising planting geometry, followed by PR1, compared to the normal sowing method. A random forest model trained on above-ground available data can predict pod yield with greater accuracy at the 75th day after sowing in PR2. The findings highlight the potential of paired-row planting to improve groundnut productivity and resilience in SAT landscapes. However, collaborative efforts among governments, research institutions, community organisations, and farmers are essential to scale up paired-row planting for groundnuts, to increase productivity at the landscape level and thereby support the livelihoods of smallholder farmers.
Efficient nitrogen use is essential for maximizing profitability in maize production while minimizing environmental impacts. The nitrogen nutrition index (NNI) and radiation use efficiency (RUE) are key indicators used to assess nitrogen status and biomass production efficiency. However, their quantitative relationship remains insufficiently understood under diverse nitrogen conditions. In this study, field experiments were conducted in Morioka, Japan, during 2020 and 2021 using five nitrogen application rates and multiple maize varieties. Nitrogen concentration and NNI were determined, and RUE was calculated, at multiple growth stages through destructive sampling. A segmented regression model was applied to analyze the relationship between NNI and RUE based on 160 observations. Despite some variability, a consistent pattern was observed: RUE declined when NNI fell below the threshold. The segmented linear regression model captured the impact of nitrogen deficiency on RUE and identified a critical threshold value for NNI. RUE decreased by approximately 0.48 g MJ-1 for every 0.1-unit decrease in NNI below the threshold value of 1.07. This finding supports the use of NNI not only as an indicator of nitrogen status but also as a quantitative predictor of maize biomass production under varying nitrogen supply conditions. Fertilizer management strategies can be optimized by quantifying expected yield losses associated with suboptimal NNI and comparing them with current nitrogen application practices.
Precision agriculture predominantly relies on aboveground data, limiting the direct detection of growth constraints caused by subsurface soil conditions. To improve understanding of spatiotemporal root systems dynamics, we aimed (1) to evaluate the relationship and relative performance of a minirhizotron method using deep learning-based image analysis in comparison with the trench profile method, with soil core sampling used as a common reference, based on statistical comparisons of association strength, regression structure, and error-based accuracy metrics; and (2) to determine whether two-dimensional root distribution dynamics can be captured using images from five minirhizotron tubes installed perpendicular to the planting row. Deep learning-based image analysis accurately extracted roots from minirhizotron images, eliminating interference from water droplets and soil color variation. The minirhizotron method showed a stronger association with core sampling than the trench profile method, as confirmed by statistical comparison of dependent correlations. Error-based accuracy metrics derived from Deming regression consistently demonstrated lower prediction errors for the minirhizotron method across soil depths and growth stages, indicating superior predictive performance relative to the trench method. Furthermore, we successfully predicted two-dimensional root distribution dynamics (approximately 90 cm in width and 60 cm in depth). Although the minirhizotron method tended to overestimate roots below 30 cm after the heading stage, previous studies suggest that root observations within the top 30 cm during stem elongation are sufficient to detect cultivar and environmental differences. These findings demonstrate that deep learning-assisted minirhizotron imaging provides a reliable, non-destructive approach for monitoring root distribution dynamics in agricultural fields.
Unmanned aerial vehicle (UAV)-based remote sensing is useful to understand crop growth conditions or grain yield potential, and monitoring forage maize (Zea mays L.) is particularly advantageous because its tall canopy makes manual measurements time-consuming. This study aimed to identify the optimal timing for effectively detecting maize growth variability using aerial photogrammetry with a UAV. We conducted weekly aerial photography of a maize field under variable nitrogen conditions to produce artificial growth differences. The results showed that the crop surface model (CSM) could effectively visualize maize growth differences after exceeding approximately 1.0 m, which corresponded to the internode elongation stage. Moreover, the determination coefficient between temporal CSM values and grain yield reached a peak of 0.7 approximately one week before silking. These results suggest that approximately one week before silking is the optimal time for CSM-based observations and the early detection of within-field maize growth differences and yield variability.
Canopy structure, particularly the leaf area index (LAI), is a major determinant of crop productivity because it influences light interception, photosynthetic efficiency, and overall resource use. Nondestructive measurement tools, such as plant canopy analyzers (PCA), have enabled repeated field-based assessments of canopy traits without the need for destructive sampling. This review synthesizes recent advances in the PCA-based evaluation of rice canopy dynamics and examines their integration with complementary sensing and modeling approaches. PCA-derived parameters have been effectively used to characterize genotypic variation in leaf expansion and to parameterize growth models, thereby supporting yield prediction and physiological interpretation. Recent advances in nondestructive profiling have enabled more accurate estimation of vertical LAI distribution, linking canopy architecture to light-use efficiency and overall productivity. Although PCA measurements require careful calibration and are constrained by labor intensity, they remain valuable ground-based references for scalable canopy monitoring. Integrating PCA with UAV-based and satellite remote sensing, supported by multispectral and hyperspectral data, offers substantial potential for large-area phenotyping and varietal discrimination. Evidence from multi-environment and multi-genotype trials demonstrates the feasibility of this integrated approach for quantitatively evaluating canopy development and crop performance. Collectively, these developments underscore the importance of integrating ground-based and remote sensing approaches to advance canopy physiology, precision agriculture, and crop breeding applications.
Spikelet number per unit area is the most important yield component of rice (Oryza sativa L.). While spikelet number in rice is often related to total N content in whole plant, several studies have reported that it is more strongly correlated with dry weight (DW). The aims of this study are to identify the most critical factor determining spikelet number and to evaluate cultivar differences in spikelet production efficiency. In a simple yet unique experiment, we investigated the relationships between spikelet number, DW, and N content of the same plants at heading stage in 27 cultivars. In all cultivars except Tsukisuzuka, with an extremely short panicle, DW at heading stage had a clear proportional relationship with spikelet number. N content had no consistent relationship with spikelet number. The constant of the proportionality between DW and spikelet number estimated from our 2-year dataset at a single site agreed with that estimated from multisite data in previous studies. We concluded that DW at heading was the most critical factor determining spikelet number. Its proportional relationship can be used as a simple model for predicting spikelet number. The proportionality constant reflected cultivar differences in spikelet production efficiency. This study not only settles the question of the most critical factor determining spikelet number, but also efficiently evaluated cultivar differences in spikelet production efficiency, which we expect to contribute significantly to regulating spikelet number in rice.
In devising a suitable nitrogen (N) fertilisation method to reduce environmental impacts, the N supply must be optimized to meet the demand for crop production. Sweet corn (Zea mays L.) was grown using different fertilisation methods and winter cover crops from 2021 to 2023. Hairy vetch (HV; Vicia villosa Roth.) and rye (Secale cereale L.) were mixed-sown at the rate of HV:rye = 50:50 and 70:30 kg center dot ha-1 in September 2021 and 2022, respectively. In addition, different fertiliser treatments - a mixture of poultry manure and bark manure (manure), polymer-coated urea fertiliser (slow-release fertiliser), and ammonium sulfate (fast-release fertiliser) - were applied before seeding sweet corn in May 2022 and 2023. Soil inorganic N, microbial biomass nitrogen (MBN), and N absorption of corn were measured during the corn growing seasons. In both years, inorganic N in the soil treated with fast-release fertiliser increased drastically and leached into the 30-60 cm soil layer at the corn seeding stage. The N supply from manure or slow-release fertiliser gradually increased inorganic N in the soil. MBN was highest in the soil surface layer where manure was applied. The N uptake rate was the highest just before the reproductive stage. The 100-grain weight was slightly lower when slow-release fertiliser was applied because of the delay in N supply. The combination of cover crops and manure was found to be preferable to the application of commonly used fast-release fertiliser to maximize corn yield while reducing environmental impacts.
The source capacity affects grain yields. Many efforts have been made to enhance grain yields by introducing quantitative trait loci (QTLs) responsible for shoot-related traits associated with source capacity. Root-related traits could improve the source capacity by improving the uptake of water and nutrients; however, studies have been limited. In this study, to elucidate the root traits related to source capacity in paddy fields, we conducted a physio-morphological analyses and field trials for yield-related traits for three years. We evaluated high-yielding lowland rice, IR64, along with four near-isogenic lines (NILs) and pyramiding lines (PYLs) that introduced upland rice alleles for four root QTLs (root growth angle, thickness, length, and volume). DRO1-NIL with the root growth angle QTL, DEEPER ROOTING 1 (DRO1), exhibited a larger rooting depth index (RDI) but a shorter total root length (TRL) than IR64. qRL6.1-NIL with a root length QTL, qRL6.1, displayed a similar RDI but a longer TRL than IR64. In contrast, qRL6.1+DRO1-PYL with both DRO1 and qRL6.1 not only had a larger RDI than IR64 but also a TRL comparable to that of IR64. qRL6.1+DRO1-PYL significantly increased grain weight per plant compared to IR64; however, neither of the NILs improved grain weight per plant. Furthermore, qRL6.1+DRO1-PYL exhibited a higher bleeding rate and nitrogen content, along with an integrated net CO2 assimilation rate (Aall) superior to that of IR64, which may have contributed to its enhanced source capacity. Our study highlights that pyramiding root QTLs has the potential to enhance source capacity, including photosynthetic ability.
Drought stress poses a major threat to the morphological and physiological processes of wheat. Vermicompost application can help alleviate these effects under water scarcity. This study investigated the protective role of rice straw vermicompost on the nutritional, biochemical, morphological, and physiological traits of wheat seedlings exposed to different drought levels. Three drought regimes - control (CK, 70% field capacity), moderate drought (MD, 45% field capacity), and severe drought (SD, 30% field capacity) - were combined with four vermicompost treatments - RVC-0 (control, no vermicompost), RVC-1 (4 t ha- 1), RVC-2 (6 t ha- 1), and RVC-3 (8 t ha- 1), applied to two wheat cultivars, Faisalabad-08 and Galaxy-13. Vermicompost application significantly improved growth traits, including root and shoot fresh and dry weights, with the most pronounced effects observed at RVC-2, under both moderate and severe drought conditions. RVC-2 also resulted in the highest stomatal conductance and chlorophyll content in both cultivars. Under severe drought, RVC-2 increased stomatal conductance by 14.38%, sub-stomatal CO2 concentration by 11.36%, total chlorophyll by 11.55%, carotenoids by 7.63%, and ascorbate peroxidase activity by 26.74% compared with the control. Moreover, RVC-2 enhanced the uptake of essential nutrients (N, P, and K) under both well-watered and drought conditions. Overall, Faisalabad-08 demonstrated greater drought tolerance than Galaxy-13, as reflected in its superior morphological, physiological, and biochemical performance. The study concludes that rice straw vermicompost, particularly at 6 t ha- 1 (RVC-2), is effective in mitigating the adverse effects of drought on wheat growth and physiology.
Chloroplasts, mitochondria, and peroxisomes are consistently positioned in close proximity with physical contact in mesophyll cells, as shown by two-dimensional transmission electron microscopy observations. However, the three-dimensional arrangement of these organelles has not yet been investigated in rice. In this study, we investigated the positions and proximity of the chloroplasts, mitochondria, and peroxisomes in rice mesophyll cells three-dimensionally. Chloroplasts aligned along the cell walls, and mitochondria and peroxisomes were located on the intracellular side of the cell rather than in the peripheral chloroplasts. In total, 345 mitochondria were included in nine replicated cells, and 89.4% of the mitochondria formed binary complexes with peroxisomes. Binary complexes were located between the chloroplasts, forming clusters in the three organelles. Among the 134 chloroplasts and 210 peroxisomes detected in the nine mesophyll cells, only one chloroplast and one peroxisome were not included in the clusters. The clustering of chloroplasts, mitochondria, and peroxisomes at a high frequency has not been observed in other plants; therefore, this arrangement is considered to be unique to rice mesophyll cells, likely due to the smaller and denser cells than those of other plants. In the clusters, the three organelles were in contact with each other and in close membrane proximity. Considering the high correlation between the total volumes of mitochondria and peroxisomes and the area of membrane proximity among the three organelles, it is suggested that the proximity areas in rice mesophyll cells are determined by the size of the binary complexes within the clusters.
