Plant biostimulants have received attention as sustainable alternatives to chemical fertilizers. Extracellular polymeric substances (EPSs), among the compounds secreted by plant growth-promoting rhizobacteria (PGPRs), are assumed to alleviate abiotic stress. This study aims to investigate the effect of purified EPSs on rice under abiotic stress and analyze their mechanisms. A pot experiment was conducted to elucidate the effects of inoculating EPSs purified from PGPRs that increase biofilm production in the presence of sugar on rice growth in heat-stress conditions. Since all EPSs showed improvement in SPAD after the stress, Enterobacter ludwigii, which was not characterized as showing higher PGP bioactivities such as phytohormone production, nitrogen fixation, and phosphorus solubilization, was selected for further analysis. RNA extracted from the embryos of germinating seeds at 24 h post-treatment with EPSs or water was used for transcriptome analysis. The RNA-seq analysis revealed 215 differentially expressed genes (DEGs) identified in rice seeds, including 139 up-regulated and 76 down-regulated genes. A gene ontology (GO) enrichment analysis showed that the enriched GO terms are mainly associated with the ROS scavenging processes, detoxification pathways, and response to oxidative stress. For example, the expression of the gene encoding OsAAO5, which is known to function in detoxifying oxidative stress, was two times increased by EPS treatment. Moreover, EPS application improved SPAD and dry weights of shoot and root by 90%, 14%, and 27%, respectively, under drought stress and increased SPAD by 59% under salt stress. It indicates that bacterial EPSs improved plant growth under abiotic stresses. Based on our results, we consider that EPSs purified from Enterobacter ludwigii can be used to develop biostimulants for rice.

Developing multi-functional, environmentally friendly biofertilizers can help reduce chemical fertilizer usage. This study examined single and combined application effects of four plant growth-promoting rhizobacteria (PGPR) strains: AF124 (Rhizobium daejeonense), AF74 (Enterobacter cloacae), AF96 (Pseudomonas putida), and AF42 (Enterobacter cloacae), isolated from alkaline salt-stressed soils from Afghanistan. Physiological features such as nitrogen (N₂) fixation, indole-3-acetic acid (IAA), organic acid production, and P and K solubilization of bacteria in single or combined cultures in vitro were examined. A single application of AF124 and AF74 showed significantly higher IAA production than the combined application of dual, triple, and quadruple PGPR treatments. Regarding acetylene reduction activity, an N₂-fixation activity indicator, a single application of AF124 showed the highest value, followed by a triple application of AF124 + AF96 + AF42. The P-solubilization activity and organic acid production were lower in the single application of AF124 but higher with other strains in the combined applications, which resulted in the secretion of multiple organic acids into the medium. The highest solubilized K value was obtained from the quadruple application compared to other treatments. In the rice inoculation test, all single and combined PGPR treatments increased its growth parameters, such as root length and root and shoot dry biomass. The present results indicate that these four PGPR strains can potentially contribute to developing multi-functional bio-fertilizer formulations.

Heat stress is a critical limiting factor in rice production, and a comprehensive understanding of the physiological traits contributing to yield under such conditions remains incomplete. This study evaluated the effects of heat stress on six rice varieties: Nagina22 (N22), NERICA4 (NER), Nipponbare (NPB), IR64, Berenj-I-Mahin (BIM), and Berenj-I-Luk (BIL) exposed to maximum temperatures exceeding 40 °C from flowering to the grain-filling stage. Results demonstrated a strong correlation between the photosynthetic rate and both 1000-grain weight and transpiration rate at the flowering stage across all varieties. Under heat stress, NER, BIM, BIL, and IR64 exhibited elevated levels of malondialdehyde, indicative of oxidative damage, and sustained significant heat injury compared to ambient conditions. Heat stress notably impaired pollen viability and spikelet fertility, reducing crop yields. In contrast, the heat-tolerant variety N22 maintained the highest spikelet fertility rate, effectively regulated transpiration cooling, and significantly enhanced yield by maintaining a lower leaf temperature. The findings indicate that photosynthetic efficiency and oxidative stress during the flowering stage critically influence spikelet fertility and overall yield in rice under heat stress. This research provides valuable insights for rice breeders and agronomists, encouraging the development of heat-tolerant varieties and adaptive strategies to mitigate the adverse impacts of elevated temperatures during critical reproductive stages.

Common beans are a vital source of protein, vitamins, and minerals. Increasing common beans productivity is crucial for improving food security and farmers’ incomes globally. This study evaluated the growth and yield responses of common beans to integrated organic and inorganic fertilizers under field conditions at the Faculty of Agriculture, Kabul University. The trial was repeated over two consecutive growing seasons in 2020 and 2021, using a randomized complete block design with 18 treatments and three replications. The fertilizers used included urea (N) (0, 60, and 90 kg/ha), diammonium phosphate (D) (0, 50, and 100 kg/ha), and farmyard manure (O) (0 and 5000 kg/ha). The results show that integrated fertilizers, particularly O5000N60D50, O5000N60D100, O5000N90D50, and O5000N90D100, significantly increased growth and yield parameters. In 2020, the grain yield increased significantly (p < 0.05) by 75.6, 76.7, and 68.4% with the O5000N60D50, O5000N60D100, and O5000N90D100 treatments, respectively. In 2021, O5000N60D50, O5000N60D100, and O5000N90D50 showed significant yield increases of 94.7, 89.6, and 97.9%, respectively. The grain yield strongly correlated with the SPAD value (r = 0.84), number of pods per plant (r = 0.71), and number of seeds per pod (r = 0.66) in 2020, and it more strongly correlated with the SPAD value (r = 0.91), number of pods per plant (r = 0.77), and number of seeds per pod (r = 0.76) in 2021. A principal component analysis highlighted the effectiveness of organic–inorganic fertilizer combinations, particularly O5000N60D50, in enhancing productivity while potentially reducing inorganic fertilizer application. This study demonstrates that integrating organic and inorganic fertilizers enhances sustainable crop productivity and reduces negative environmental impacts, particularly in regions facing nutrient depletion and drought conditions.

The increased frequency of extreme heat stress events due to climate change is adversely impacting rice yield. Nitrogen (N) is an essential element in the synthesis of chlorophyll in rice, contributing substantially to the achievement of spikelet fertility and addressing the high yields. Two experiments were conducted in Japan and Afghanistan in 2020 and 2022, respectively, utilizing IR64 and Nipponbare (NPB) varieties to elucidate the efficacy of N top-dressing on spikelet fertility and yield of rice under heat stress conditions. In experiment I, the treatments involved were based on N application before panicle emergence in pots, including (1) control (fertilized at the tillering stage), (2) control + N topdressing, (3) heat stress (fertilized at the tillering stage), and (4) heat stress + N topdressing. Experiment II consisted of (1) control (basal dressing at the tillering stage) and (2) control + N topdressing, which was conducted under field conditions. Results showed that N application significantly (p < 0.05) increased SPAD values and spikelet fertility rates in both experiments. A positive correlation (range; r = 0.83–0.98) was observed between enhanced SPAD values and spikelet fertility rates in IR64 and NPB rice varieties under both ambient and heat stress conditions. Moreover, there were notable increases in photosynthetic rate (7.4% to 52.6%) and leaf transpiration. N top dressing significantly (p < 0.05) increased the panicle length, panicle weight, number of secondary branches/panicle, filled grain/panicle, total spikelets/panicle, and yield/plant. However, there was no significant difference in the number of primary branches per panicle and 1000-grain weight. In addition, the number of unfilled grains/panicle decreased from 5.5 to 49.7% with N top dressing in both experiments. Applying N as a top dressing improved the spikelet fertility percentage and other yield components, resulting in a high yield/plant.

The excess application of chemical fertilizer contributes to environmental pollution. Therefore, this study aims to explore the integrated use of animal manure and chemical fertilizer to identify a more sustainable and environmentally friendly alternative to nitrogen fertilizer. Two experiments were conducted in 2018 and 2019 at Kabul University, Afghanistan, using an LD04-13265 soybean variety. The integration of animal manure and chemical fertilizer was categorized into six treatments: (1) control (no fertilizer), (2) animal manure low dose (AMLD), (3) animal manure high dose (AMHD), (4) chemical fertilizer (CF), (5) CF 50% + AMLD, and (6) CF 75% + AMLD. The results revealed that AMHD and its integration with 75% chemical fertilizer greatly influenced the vegetative growth of soybean plants in experiments I and II. The number of pods per plant and pod length significantly (p < 0.05) increased under the CF 75% + AMLD treatment. In experiment I, soybean yield increased the most with the CF treatment, followed by CF 75% + AMLD. In contrast, in experiment II, the highest yield per hectare was observed in the CF 75% + AMLD treatment, followed by CF. The CF 75% + AMLD treatment significantly increased the SPAD value in both experiments. Consequently, a strong relationship was observed between the SPAD value and yield (r = 0.74) in experiment I and between SPAD and pod length (r = 0.82) in experiment II. Incorporating animal manure with chemical fertilizer significantly impacted soybean growth and yield, offering a potential possibility for reducing reliance on nitrogen fertilizer application to mitigate environmental pollution.