Search Results (315)

Azospirillum is a well-studied genus of plant growth-promoting rhizobacteria (PGPR) and one of the most extensively researched diazotrophs. This genus can colonize rhizosphere soil and enhance plant growth and productivity by supplying essential nutrients to the host. Azospirillum–plant interactions involve multiple mechanisms, including nitrogen fixation, the production of phytohormones (auxins, cytokinins, indole acetic acid (IAA), and gibberellins), plant growth regulators, siderophore production, phosphate solubilization, and the synthesis of various bioactive molecules, such as flavonoids, hydrogen cyanide (HCN), and catalase. Thus, Azospirillum is involved in plant growth and development. The genus Azospirillum also enhances membrane activity by modifying the composition of membrane phospholipids and fatty acids, thereby ensuring membrane fluidity under water deficiency. It promotes the development of adventitious root systems, increases mineral and water uptake, mitigates environmental stressors (both biotic and abiotic), and exhibits antipathogenic activity. Biological nitrogen fixation (BNF) is the primary mechanism of Azospirillum, which is governed by structural nif genes present in all diazotrophic species. Globally, Azospirillum spp. are widely used as inoculants for commercial crop production. It is considered a non-pathogenic bacterium that can be utilized as a biofertilizer for a variety of crops, particularly cereals and grasses such as rice and wheat, which are economically significant for agriculture. Furthermore, Azospirillum spp. influence gene expression pathways in plants, enhancing their resistance to biotic and abiotic stressors. Advances in genomics and transcriptomics have provided new insights into plant-microbe interactions. This review explored the molecular mechanisms underlying the role of Azospirillum spp. in plant growth. Additionally, BNF phytohormone synthesis, root architecture modification for nutrient uptake and stress tolerance, and immobilization for enhanced crop production are also important. A deeper understanding of the molecular basis of Azospirillum in biofertilizer and biostimulant development, as well as genetically engineered and immobilized strains for improved phosphate solubilization and nitrogen fixation, will contribute to sustainable agricultural practices and help to meet global food security demands. Full article

Soybean (Glycine max) is a protein-rich legume crop that plays an important role in achieving food security. The aim of this study was to isolate soybean-nodulating rhizobia from Côte d’Ivoire soils and evaluate their potential as efficient strains in order to develop local bioinoculants. For this objective, 38 composite soil samples were collected from Côte d’Ivoire’s five major climatic zones. These soils were used as substrate to trap the nodulating rhizobia using the promiscuous soybean variety R2-231. A total of 110 bacterial strains were isolated and subsequently identified. The analysis of ITS (rDNA16S-23S), glnII and recA sequences revealed a relatively low genetic diversity of these native rhizobia. Moreover, the ITS phylogeny showed that these were scattered into two Bradyrhizobium clades dominated by the B. elkanii supergroup, with ca. 75% of all isolates. Concatenated glnII-recA sequence phylogeny confirmed that the isolates belong in the majority to ‘B. brasilense’, together with B. vignae and some putative genospecies of Bradyrhizobium that needs further elucidation. The core gene phylogeny was found to be incongruent with nodC and nifH phylogenies, probably due to lateral gene transfer influence on the symbiotic genes. The diversity and composition of the Bradyrhizobium species varied significantly among different sampling sites, and the key explanatory variables identified were carbon (C), magnesium (Mg), nitrogen (N), pH, and annual precipitation. Based on both shoot biomass and leaf relative chlorophyll content, three isolates consistently showed a higher symbiotic effectiveness than the exotic inoculant strain Bradyrhizobium IRAT-FA3, demonstrating their potential to serve as indigenous elite strains as bioinoculants. Full article

Protists represent a major component of eukaryotic diversity within the soil microbiome, playing critical roles in mediating carbon and nitrogen cycling and influencing nutrient availability and soil health. Their diversity is shaped by multiple factors, including temperature, pH, organic matter content, and land use. In this study, we investigated the protist diversity in rhizosphere soils from both wild and cultivated date palm varieties. Our results identified nitrate, nitrite, calcium, and carbon content as key soil factors significantly correlated with protist diversity. Only 9.2% (42) of operational taxonomic units (OTUs) were shared across all soil samples, suggesting that these taxa possess traits enabling adaptation to extreme environmental conditions. The dominant protist families belonged to Rhizaria, Alveolata, Amoebozoa, and Archaeplastida, primarily comprising bacterial consumers, alongside taxa from Stramenopiles, Opisthokonta, Hacrobia, and Excavata. At the class level, Filosa-Sarcomonadea, Colpodea, Variosea, Tubulinea, and Chlorophyceae were the most abundant. Filosa-Sarcomonadea and Colpodea were positively correlated with bacterial and fungal genera, suggesting their role as consumers, while Variosea showed a negative correlation with bacteria, reflecting predator-prey dynamics. Notably, the protist community composition in wild date palm rhizosphere soils was distinct from that in cultivated soils, with Opisthokonta being particularly abundant, likely reflecting adaptation to drought conditions. Overall, this study highlights the significant differences in protist diversity and community structure between wild and cultivated date palm ecosystems. Full article

This study evaluated the effects of one-time application of controlled-release fertilizer (CRF) on rice (Oryza sativa L.) grain yield, grain quality, and agronomic nitrogen use efficiency (ANUE, ANUE (kg/kg) = (Grain yield with N application − grain yield without N application)/N application amount) in coastal saline soils. A two-year field experiment (2023–2024) was conducted using two rice varieties (Nanjing 5718 and Yongyou 4953) under four nitrogen treatments: N0 (no nitrogen fertilization), N1 (270 kg·hm⁻², with a ratio of 5:1:2:2 at 1-day before transplanting, 7-day after transplanting, panicle initiation, and penultimate-leaf appearance stage, respectively), N2 (270 kg·hm⁻², one-time application at 1-day before transplanting as 50% CRF with 80-day release period + 50% urea), and N3 (270 kg·hm⁻², 50% one-time application of CRF with 120-day release period at the seedling stage + 50% urea at 1-day before transplanting). Compared with N1, the N3 treatment significantly increased grain yield by 10.2% to 12.9% and improved ANUE by 18.5% to 51.6%. It also improved processing quality (higher brown rice, milled rice, and head rice rates), appearance quality (reduced chalkiness degree and chalky rice percentage), and taste value (by 19.3% to 31.2%). These improvements were associated with lower amylose, protein, and soluble sugar contents and favorable changes in starch composition and pasting properties. While N2 slightly improved some quality traits, it significantly reduced yield and ANUE. Correlation analysis revealed that starch and protein composition, as well as pasting properties, were significantly associated with taste value and related attributes such as appearance, stickiness, balance degree, and hardness. Overall, one-time application of CRF with a 120-day release period at the seedling stage, combined with basal urea, offers an effective strategy to boost yield, quality, and ANUE in coastal saline rice systems. Full article

Oats (Avena sativa L.) are forage grasses moderately tolerant to saline-alkali soil and are widely used for the improvement and utilization of saline-alkali land. Using the oat varieties collected from the Qaidam Basin as experimental materials, based on the analysis data of the main agronomic traits, quality, and soil physical and chemical properties of different oat varieties at the harvest stage. The hay yield of Molasses (17,933.33 kg·hm⁻²) was the highest (p < 0.05), the plant height (113.59 cm) and crude fat (3.02%) of Qinghai 444 were the highest (p < 0.05), the fresh-dry ratio (2.62), crude protein (7.43%), and total salt content in plants (68.33 g·kg⁻¹) of Qingtian No. 1 were the highest (p < 0.05), and the Relative forage value (RFV) of Baler (122.96) was the highest (p < 0.05). In the 0–15 cm and 15–30 cm soil layers of different oat varieties, the contents of pH, EC, total salt, Ca²⁺, Mg²⁺, and HCO₃⁻ showed a decreasing trend at the harvest stage compared to the seedling stage, while the contents of organic matter, total nitrogen, Cl⁻, and SO4²⁻ showed an increasing trend. The contents of K⁺ and Na⁺ maintained a relatively balanced relationship between the seedling stage and the harvest stage in the two soil layers. Qingtian No. 1, Qingyin No. 1, and Molasses all rank among the top three in terms of production performance and soil physical and chemical properties, and they are the oat varieties suitable for cultivation in the research area. Full article

Optimizing the efficiency of fertilizer use is critical for sustainable maize production and food security, particularly in smallholder systems. Sub-optimal application rates pose a significant risk of soil nutrient depletion and low productivity. Split plot experiments were conducted across four locations in Ghana’s Guinea Savannah using seven maize varieties from three different maturity classes. The study assessed the response to nitrogen fertilizer applications (0, 60, 90, and 120 kg N ha⁻¹) regarding yield, Agronomic Efficiency (AE_N), Water Use Efficiency (WUE), and economic feasibility. Grain yields across locations and varieties demonstrated a strong linear response to nitrogen fertilization. The 90 kg N ha⁻¹ application generally produced the highest AE_N for all sites and varieties. Gross Revenue (GR) and WUE increased with higher N rates, with Value-to-Cost Ratios (VCR) consistently exceeding 2. Applying 90 kg N ha⁻¹ resulted in statistically similar Gross Revenues (GRs) to the 120 kg N ha⁻¹ fertilization. Different maturity classes significantly impacted fertilizer efficiency in semi-arid Ghana, with intermediate varieties outperforming extra-early ones. Though a 90 kg N ha⁻¹ rate was generally identified as the economically optimal rate of N fertilization for the locations, targeted fertilizer recommendations based on maize maturity groups and location are strongly advised. Full article

Soybeans have been cultivated in Poland for more than 140 years. However, Poland’s cold and water-deficient climatic conditions hinder soybean cultivation. Although the availability of suitable soybean varieties in Poland contributes to meeting the demand for soybean production, it is important to identify rhizobial inoculants in Polish soils suitable for soybean cultivation. In this study, we cultivated soybean varieties (Abelina, Merlin, and Sultana) grown in soils taken from four regions in Poland and isolated 330 strains from soybean root nodules. 16S rRNA gene sequencing identified 49 strains of highly stress-tolerant nodule-associated bacteria, including Bradyrhizobium, Rhizobium, Ensifer, Tardiphaga, and Ralstonia spp. Several isolates exhibited positive effects on soybean growth under cold and water-deficient conditions. In particular, the isolate Bradyrhizobium japonicum PSN49, which is phylogenetically similar to B. japonicum USDA 123, increased plant biomass and nodule formation in the soybean cultivar Abelina under abiotic stress conditions due to its high nitrogen-fixing activity. Whole-genome comparisons between PSN49 and other Bradyrhizobium strains revealed that trehalose biosynthesis genes and cold shock proteins contributed to cold stress tolerance. These findings and the strains identified in this study will enhance soybean production and deepen the understanding of the soybean–rhizobium relationship in Poland. Full article

This study systematically investigates the mechanistic effects of multifactor interactions (including soil properties, climatic conditions, and cultivation practices) on the productivity parameters (grain yield, stover yield, dry biomass, harvest index) of maize cultivars of different maturity groups in the arid region of Xinjiang, China. Twelve representative maize-growing counties were selected as study sites, where we collected maize samples to measure HI, grain yield, stover yield, and soil physicochemical properties (e.g., organic matter content, total nitrogen, and available phosphorus). Additionally, climate data (effective accumulated temperature) and agronomic parameters (planting density) were integrated to comprehensively analyze the interactive effects of multiple environmental factors on HI using structural equation modeling (SEM). The results demonstrated significant varietal differences in HI across maturity periods. Specifically, early-maturing cultivars showed the highest average HI (0.58), significantly exceeding those of medium-maturing (0.55) and late-maturing varieties (0.54). Environmental analysis further revealed that soil phosphorus content (both available and total phosphorus), elevation, and organic matter content significantly positively affected HI, whereas soil bulk density and electrical conductivity exhibited negative impacts. Notably, HI exhibited a strong negative correlation with stover yield (R² = 0.49), but remained relatively stable across different dry matter (DM) and grain yield levels. Despite the strong positive correlation between DM and grain yield (R² = 0.81), the relative stability of HI suggests that yield improvement requires balanced optimization of both DM and partitioning efficiency. This study provides crucial theoretical foundations for optimizing high-yield maize cultivation systems, regulating fertilizer application rates and their ratios, and improving the configuration of planting density in arid regions. These findings offer practical guidance for sustainable agricultural development in similar environments. Full article

Agricultural systems exhibit a large degree of within-field yield variability. We require a better understanding of the drivers of this variability in order to optimally manage croplands. We investigated drivers of sub-field spatial variability in yield for three crops (hard red winter wheat, Triticum aestivum L. variety Langin; corn, Zea mays L.; and proso millet, Panicum milaceum L.) usings a multi-year dataset from a dryland research farm in northeastern Colorado, USA. The dataset spanned 18 2.6–4.3 ha management units, over 4 years, and included high-resolution topographic data, densely sampled soil properties, and on-site weather data. We modeled yield for each crop separately using random forest regression and evaluated model performance using spatially blocked cross-validation. The topographic position index (TPI) and increasing percent sand had a strong negative effect on yield, while the nitrogen application rate (N) and total soil carbon had strong positive effects on yield in both the wheat and millet models. Remarkably, TPI had almost as large of an effect size as N, and outperformed other more commonly used topographic predictors of yield such as the topographic wetness index (TWI), elevation, and slope. Despite the size and quality of our dataset, cross-validation results revealed that our models account for approximately one-quarter of the total yield variance, highlighting the need for continued research into drivers of spatial variability within fields. Full article

Salinity stress severely limits maize (Zea mays L.) productivity, necessitating sustainable mitigation strategies to ensure food security in affected regions. This study investigates the efficacy of compost (5 and 10 t/ha) and plant growth-promoting rhizobacteria (PGPR; Azospirillum brasilense) in enhancing maize productivity and soil health under salinity stress (EC_e 3.5 and 6.3 dS/m) across three varieties (Single Cross 131, 132, and 178) in field experiments conducted in 2023 and 2024. Combined compost-10 + PGPR treatment significantly increased grain yield by up to 197% and straw yield by nearly 300% in Single Cross 178 under high salinity, surpassing single treatments. Nitrogen content in grains and straw rose by 157%, while proline, peroxidase activity, and chlorophyll content improved, indicating robust stress tolerance. Soil properties, including pH, EC_e, sodium adsorption ratio, and exchangeable sodium percentage, were significantly ameliorated, with bulk density reduced and porosity increased. Soil organic matter and microbial populations (bacteria and fungi) were also enhanced. Single Cross 178 exhibited superior stress tolerance, highlighting varietal differences. These findings, supported by comparisons with the existing literature, underscore the synergistic role of compost and PGPR in improving nutrient uptake, antioxidant defenses, and soil structure. This study offers a sustainable strategy for maize cultivation in saline environments, with implications for global food security. Full article

In the 2020 and 2021 vintages, some chemical and phytochemical parameters of the Aglianico and Cabernet Sauvignon cultivars grown in three regions of Southern Italy (Campania, Molise, and Sicily) were determined. In particular, the aim of this study was the investigation of flavanol, monomeric anthocyanin, and pigment contents in grapes and wines. The data collected showed that the main chemical parameters and flavonoids analyzed in the grapes and wines were influenced by the vintage, grape variety, and geographical location. Specifically, in the Aglianico grapes, the latitude and vintage highly influenced the titratable acidity and flavonoids in terms of richness in flavanols, compared to Cabernet Sauvignon. On the other hand, the location of the vineyard influenced monomeric anthocyanins in both varieties, highlighting a relationship of these phytochemicals with soil fertility and availability of certain chemical elements such as nitrogen and iron. All results support the idea that the interaction between grape variety, soil type, and geographical origin plays a decisive role in shaping the characteristics of wine. Full article

In this study, the melon variety ‘Da Shetou’ was used as the test material, and pot cultivation was employed with soil collected from Da’an City to investigate the effects of biochar addition on melon yield and quality, rhizosphere soil physicochemical properties, and soil microbial community. The experiment was set up with five treatments: saline–alkali soil (B0), 1% biochar and 99% saline–alkali soil (B1), 3% biochar and 97% saline–alkali soil (B3), 5% biochar and 95% saline–alkali soil (B5), and 7% biochar and 93% saline–alkali soil (B7). This study found that the addition of 3% biochar increased the fruit yield of melons. Compared to the control, the soil bulk density was reduced by 4.99%, 8.66%, 1.77%, and 7.71% under the 1%, 3%, 5%, and 7% biochar treatments, respectively. Biochar addition increased organic matter, alkaline-hydrolyzable nitrogen, available phosphorus, and available potassium concentrations in the rhizosphere soil. Additionally, the total nitrogen, salt concentration, and exchangeable sodium percentage were also reduced. Compared to the B0 treatment, the concentrations of K⁺, Ca²⁺, and Mg²⁺ increased to varying degrees across different treatments, while the concentrations of Na⁺ and Cl⁻ decreased. The relative abundance of dominant bacterial phyla in the soil varied across different treatments. The dominant bacterial phyla included Proteobacteria, Actinobacteriota, Acidobacteriota, and a total of 10 others. The dominant fungal phyla included Ascomycota, Basidiomycota, Mortierellomycota, and a total of seven others. Redundancy analysis (RDA) identified key drivers. Available potassium in the rhizosphere soil of melons was the dominant factor influencing bacterial community composition at the phylum level. Soil bulk density, exchangeable sodium percentage, and total nitrogen were identified as the dominant factors influencing fungal community composition at the phylum level. This study confirmed that 3% biochar application synergistically regulated nutrient cycling and microbial functional groups, thereby enhancing yield of thin-skinned melons (yield increase: 45.22%). Full article

Soil, as the foundation for the survival of understory ginseng, directly impacts its growth and development. However, studies focusing on the role of soil in determining the quality of understory ginseng are limited. This study examines the relationship between quality and yield of 5-, 9-, and 17-year-old understory ginseng and their soil microbiota. The results indicate that with the increase in growth years, the overall biomass of understory ginseng generally shows an upward trend, while its quality slightly decreases at 9 years. Compared to the other two growth years, the soil from 9-year-old ginseng shows lower enzyme activity and pH and a higher abundance of pathogens. The 17 years soil has higher OM and AHN content, along with increased abundance of denitrifying and nitrogen-reducing bacteria. Correlation networks reveal that AK significantly influences ginsenoside content, while AP and AHN are more closely related to soil microorganisms. Compared with other types of ginsenosides, ginsenosides Rh2 and Rd are affected by a greater variety of soil microorganisms and chemical factors. As growth years increase, the changes in ginseng quality, soil nutrients, and soil microbiota do not follow a single linear trend; instead, there appears to be a bottleneck phase at certain intermediate stages. Full article

In this study, a combined localization experiment was performed on different nitrogen application rates in rice–wheat rotation. Rice cultivar Nanjing 5718 and wheat variety Yangmai 25 were employed in this two-season study, with six and five distinct nitrogen rates designed during the rice and wheat growing seasons, respectively. Thus, a total of 30 N rate combinations were formed across the two seasons. Our findings indicate that when current-season N inputs ranged from 0 to 240 kg ha⁻¹, residual N from the preceding season contributed significantly to yield improvement (5.58–18.96% increase) for subsequent crops, primarily through enhanced panicle formation and the number of grains per spike. Conversely, high current-season N rates (360–420 kg ha⁻¹) lead to reduced yields (4.61–5.81%) in the following cropping cycle under identical N management practices. Maximizing annual crop production was achieved with a combined N regimen of 264.63 kg ha⁻¹ (rice) and 254.89 kg ha⁻¹ (wheat), yielding 14.21 t ha⁻¹. Notably, current-season N levels exhibited significant correlations with starch and protein content in both rice and wheat, whereas previous-season N application showed no comparable relationships. Furthermore, soil N storage remained stable, and the highest N use efficiency was observed under the total annual N input of 547.7 kg ha⁻¹ (rice + wheat). Full article

Farmers frequently rely on mineral fertilizers to increase yields, improve or sustain crop productivity, and mitigate the adverse impacts of environmental stresses, including salinity. However, improper fertilization—whether inadequate or excessive—can hinder plant growth, reduce nutritional quality, and contribute to soil degradation and environmental pollution. Understanding how different levels of nitrogen (N) fertilizers and abiotic stresses such as salt impact yields and end-use quality is important to maintain food production and ensure fair crop value. In this study, we examined four types of spring wheat to investigate the role of adequate N levels in salt tolerance and their effects on end-use quality. The findings revealed no uniform response to either low N or salt treatment regarding growth or grain characteristics. All aspects, including biomass reduction, yield response variations, and grain components such as protein content, starch, or fiber, were influenced by different abiotic stresses across the various backgrounds tested. In some cases, these stresses were additive, further reducing crop value in specific genetic backgrounds, while, in others, their effects were minor. We identified varieties that are relatively tolerant to lower N levels, maintaining both yields and biomass production, as well as varieties that are less sensitive to salt, allowing them to sustain yields and biomass production. This deeper understanding of these varieties can now be leveraged to breed for improved stress tolerance across the entire life cycle, further enhancing yields under suboptimal conditions and minimizing the effects of reduced N inputs and salt tolerance. Full article