ABSTRACT 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 × 10 cm; PR2-25:25 cm/50 cm × 10 cm; PR3-20:20 cm/25 cm × 10 cm; PR4-15:15 cm/22.5 cm × 10 cm, along with the standard spacing PR5-30 cm × 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.

ABSTRACT Sugarcane (Saccharum spp. hybrids) is a globally important crop for food and bioenergy, but its production is increasingly threatened by drought driven by climate change. Drought causes complex interactions between root function and leaf photosynthesis, but their underlying mechanisms remain largely unstudied in sugarcane. To address this knowledge gap, we grew up to eight sugarcane cultivars in one field and two pot experiments inside a rain-out shelter. The relative growth rate of these eight cultivars under both well-watered and water-limited conditions was largely explained by net assimilation rate, which depended on bleeding sap rate caused by root pressure. Among the cultivars, Harunoogi – a first-generation backcross cultivar between a wild relative (S. spontaneum) and a commercial cultivar – exhibited improved drought avoidance through adequate root water supply, whereas the commercial cultivar NiTn18 showed the opposite. Throughout the drought and recovery, Harunoogi exhibited significantly higher leaf area, stomatal conductance, chlorophyll content, and maximum amplitude of the reaction center chlorophyll of PSI than cultivar NiTn18, which resulted in a higher net CO₂ assimilation rate and biomass. These results highlight the potential of improving both root function and photosynthesis as an effective approach to developing drought-tolerant sugarcane in the field.

ABSTRACT Erect-panicle rice has the potential to improve rice production owing to its unique leaf canopy structure and high leaf nitrogen content (LNC). However, limiting information is available regarding its canopy photosynthesis of erect-panicle rice. In this study, we aimed to investigate the effects of leaf canopy structure and LNC on photosynthesis in erect-panicle rice under various cultivation management conditions. Field experiments were conducted using three rice cultivars – Shennong265 (erect-panicle rice), Nipponbare, and Takanari – grown under different fertilizer and planting density treatments. A modeled canopy photosynthetic rate, based on a photosynthetic model that incorporates nitrogen distribution, was used to evaluate the influence of leaf canopy structure and LNC on canopy photosynthesis. Compared to other cultivars, Shennong265 exhibited significantly higher LNC, particularly in the lower stratum, which enhanced the modeled photosynthetic rate during the ripening stage. The erect configuration of its panicles and leaves allowed increased light transmittance within the canopy and may have contributed to the maintenance of LNC in the lower stratum. Nonetheless, the canopy photosynthetic rate of Shennong265 decreased under high planting density compared with that under normal density, indicating the importance of optimizing planting density for this cultivar. These findings underscore the critical role of LNC distribution in determining the productivity of erect-panicle rice. The distinctive canopy structure of erect-panicle rice enabled sustained LNC in the lower canopy, thereby improving photosynthetic capacity. Our results demonstrate the need to carefully consider in the cultivation of erect-panicle rice to maximize its productivity advantages.

ABSTRACT Creating salt-tolerant genotypes is crucial for maximizing the productivity under salinized land. To evaluate genetic diversity for salt tolerance, 35 diverse cotton accessions were screened under 17 dS m−1 salt stress conditions using 20 agronomic and physiological traits relevant to salt tolerance. The general linear model analysis indicated significant salinity impacts across the studied accessions, and genotype × treatment effects were also significant for all parameters examined. Among all 35 studied accessions; the genotypes CCB-1, CCB-2, CCB-28, CCB-3, CCB-4, Ghauri-1, JSQ-70, and JSQ-71 showed considerably higher performance for plant height, boll per plant, boll weight, lint percentage, seed cotton yield and fiber quality traits under salt stress. Physiological traits, chlorophyll and carotenoid contents, total soluble proteins, K+, and K+/Na+ were reduced under saline conditions, while biochemical traits such as catalase, superoxide dismutase, peroxidase, H2O2 and MDA level increased. The genotypes CCB-17, CCB-18, CCB-19, CCB-20, CCB-21, CCB-22, Hatf-3, Badar-1, Eagle-2, Eagle-4, CCB-23, CCB-24, CCB-25, CCB-26 and CCB-28 exhibited lower values for agro-physiological and fiber quality character respectively, signifying their sensitivity to salt stress. Under salinity, these genotypes showed reduced antioxidant levels and increased values for K+/Na+, Na+, H2O2, and MDA contents. Whereas the genotypes CCB-5, CCB-6, CCB-7, CCB-8, CCB-9, CCB-10, CCB-11, CCB-12, CCB-13, CCB-14, CCB-15, and CCB-16 demonstrated moderate performance for these traits under salt stress conditions respectively. Utilizing multivariate analysis techniques (cluster and PCA), 35 genotypes have been categorized into three groups based on studied traits: tolerant (cluster-1), moderately tolerant (cluster-2), and susceptible (cluster-3) under saline conditions.

ABSTRACT This study evaluated the variation in grain yield and Zn concentration in rice after foliar application of Zn and the impact on its phytate : Zn molar ratio among 21 rice varieties. Rice varieties were grown under field conditions using a randomized complete block design with four replications over two cropping years in 2020 and 2021 during the rainy season. Foliar Zn application varied grain yield from −26.0 to 13.6% in 2020 and −14.7 to 30.4% in 2021 compared with non-foliar Zn. Grain Zn was varied from 0.5 to 31.1% in 2020 and from −5.9 to 47.8% in 2021 in unpolished rice and from 9.4 to 47.0% in 2020 and from 8.2 to 163.0% in 2021 in polished rice. The phytate : Zn molar ratio was decreased when foliar Zn was applied to the unpolished and polished rice, with a lower ratio in the polished rice. The phytate : Zn molar ratio decreased exponentially with increasing grain Zn concentration in the unpolished rice, while decreasing linearly with increasing grain Zn concentration in the polished rice. The results of this study suggest that foliar Zn application is a promising way to improve the grain Zn concentration and decrease the phytate : Zn molar ratio, thus being beneficial for human diets, but the effects of rice variety, cropping season, and the polishing process should be considered.

ABSTRACT The surge in global agricultural input prices, particularly for nitrogen (N) fertilizers, has presented challenges for farmers facing stagnant crop prices and rising production costs. This study explored a system designed to sustain or enhance farmers’ income while reducing production costs, with a specific focus on implementing practices that involve cultivating crops with lower rates of fertilizer than conventional rates, particularly in smaller land settings, through on-farm experimentation (OFE). OFE was conducted over three years across 11 fields in Gifu, Japan, utilizing a strip trial design to investigate the effect of fertilizer input rates on rice yield. To collect yield data, unmanned aerial vehicle (UAV)-mounted multispectral cameras were deployed. A Gaussian process model was used to address the impact of fertilizer input rates on yield while accounting for spatial yield variation. The study further assessed the number of field trials achieving positive profits at certain probability levels by integrating outcomes from multiple OFEs. The results highlighted little rice yield response to fertilizer input in most of the fields, while several fields showed significant positive yield responses. Notably, the use of lower fertilizer input rates in certain fields proved to be more profitable whereas higher fertilizer input rates were less profitable in most fields. The results further emphasized the economic viability of lower rates, especially when fertilizer prices are high, thus contributing valuable insights for sustainable and profitable rice production in Japanese cultivation.

ABSTRACT To explore field microclimate changes under maize/ginger intercropping and select a reasonable field configuration, this study used the major ginger variety ‘Zhugen’ from Southwest China as the experimental material. Two maize plant types; tall (Zhenghong 311) and short (Zhenghong 6), with 2, 3, and 4 m row spacings, shading treatment (ST), and a control (pure) without shading (CK) were used for the study. The effects of the maize plant type and row spacing on soil temperature, humidity, canopy temperature, light transmittance, plant growth, and intercropped ginger yield were investigated. Soil moisture, ginger canopy humidity, and shading rate in the maize/ginger intercropping mode were significantly higher than those in the non-shading treatment. Conversely, the soil and ginger canopy temperatures of the maize/ginger intercropping mode were significantly lower than those of the non-shading treatment. As a result, plant height, stem diameter, branch number, and ginger yield were significantly higher under the intercropping mode than the non-shading treatment. Although maize/ginger intercropping improves ginger growth and yield, these parameters are dependent on maize plant type and row spacing. The ginger yield was significantly higher when intercropped with the tall maize ZH 311 than with short maize ZH 6. The yield improved with decreasing row spacing and was the highest at a row spacing of 2 m. At the aforementioned field configurations, the soil and canopy humidity were the highest whereas the soil and canopy temperatures were the lowest, thereby giving best results on parameters like plant height, stem diameter, branch number, and yield.

ABSTRACT Direct planting (i.e. the planting of seed roots) can reduce the labor requirements of sweet potato (Ipomoea batatas (L.) Lam.) cultivation. To broaden the breeding material for high dry matter productivity in direct planting, root dry matter content (DMC) and root dry matter weight per hill (DMW) were compared under both direct planting and conventional transplanting by using 28 sweet potato genotypes cultivated in 2020 and 2021. Unlike in the case of the mother root DMC, a significant positive correlation between the daughter root DMC in direct planting and the root DMC in transplanting was observed over two years (p < 0.001). Additionally, a significant positive correlation was observed between the total root DMW in direct planting and root DMW in transplanting (p < 0.001). These results suggest that the dry matter productivity of genotypes in direct planting cultivation can be presumed from the performance of the transplanting cultivation.

ABSTRACT Inoculation with arbuscular mycorrhizal fungi (AMF) may enhance crop growth in upland fields, depending on the water regime. To quantify changes in AMF infection rate and subsequent effects on nutrient uptake and growth, we grew rice (wetland crop) and pearl millet (dryland crop) genotypes with or without the commercial inoculant Dr. Kinkon (Glomus sp. R10) in Andosol upland fields in 2020 and 2021. Root infection rates were measured in shallow (0–10 cm) and deep (20–30 cm) layers under three water regimes: well-irrigated, half-irrigated, and non-irrigated. Inoculation enhanced shoot dry weight (SDW), plant height, tiller number, phosphorus (P) uptake, leaf water potential, photosynthetic rate (measured only in 2021) and root transversal area. The increase in SDW with inoculation was higher under well-irrigated than under water-limited conditions. The increment in pearl millet SDW was related to higher P uptake associated with higher infection rates, whereas that in rice SDW was related to maintenance of leaf water potential, greater root transversal area and root length density, and higher P uptake but not to infection rate parameters. Inoculation increased mycorrhizal and vesicular infection rates with the similar tendency for arbuscular infection rate and qPCR. Infection rates were similar across water regimes in both years despite significant differences in plant growth parameters with higher rates in deep than shallow layers. AMF inoculation enhanced infection rates, mostly independent of water regime, but plant growth enhancement was greater under the well-irrigated treatment and was more directly linked with infection rates in pearl millet.

ABSTRACT Dry direct seeding of rice (DDSR) is being increasingly used in water-scarce areas across Asia. When drought occurs, deep sowing may enable germinating seeds to utilize the residual moisture below the surface. Our objective was to examine the effects of different sowing depths on DDSR crop growth. Two yield experiments, one in the Philippines and the other in Japan, were established in rainfed lowlands, but drought did not occur. Across the experiments, sowing at a depth of 6 to 7 cm reduced the percentage of emergence compared with sowing at a depth of 1 to 2 cm (25% vs. 73%), which resulted in lower yield (3.5 vs. 4.4 t ha−1). The relative yield (deep-sowing/shallow-sowing) was positively correlated with the percentage emergence under deep sowing. Cultivars with no significant yield reduction under deep sowing maintained high emergence (>30%) under deep sowing. Seedling’s ability to emerge after deep sowing greatly differed among cultivars: the percentage emergence ranging from 0% to 18% from a depth of 8 to 10 cm, and from 11% to 44% from a depth of 6 to 7 cm. An ancillary field experiment was conducted under drought during the dry season in the Philippines: deep sowing increased the percentage emergence compared with shallow sowing (41% vs. 5%), when the soil surface was severely dry. Our results suggest that choosing cultivars that can tolerate deep sowing is a prerequisite for using deep sowing in DDSR, and that future breeding of DDSR should focus on this tolerance.