Iron deficiency limits legume production on calcareous soils, and commonly used synthetic iron chelates (e.g., Fe-EDTA) are effective but non-biodegradable and may mobilize toxic metals. Microbial siderophores offer an environmentally sound alternative, yet their direct application as biofertilizers remains underexplored. Here, we evaluated the iron-carrying siderophore produced by Amycolatopsis lurida strain 407 as a biofertilizer for chickpea. Siderophore extracts were quantified and characterized by the CAS assay, Fe (III)-ICP-OES, Arnow and FeCl₃ tests, UV-Vis spectroscopy, and genome mining (antiSMASH). Results indicate strain 407 secretes a mixed catecholate-hydroxamate siderophore whose UV-Vis spectrum (200-600nm) matches mirubactin C and is supported by a mirubactin-like biosynthetic gene cluster in its closest type strain. When applied to chickpea, the Fe + siderophore from strain 407 increased root dry weight and yielded the highest shoot biomass (28g/ plant), pod/plant (41 pods), and seed/pod (36 seeds), outperforming chemical iron fertilizer, Fe-EDTA/ Sequestrin 138 (22g, 24 pods, 24 seeds). Furthermore, seed soluble protein (20mg/g dry seed) was 17% higher than with Sequestrin 138. In this study, for the first time, findings show the mirubactin-like Fe-siderophore from A. lurida 407 enhances plant growth and seed quality and represents a promising, eco-friendly alternative to synthetic iron fertilizers.

Hydroxyl radical bursts triggered by long-term nitrate accumulation accelerate deep soil organic carbon mineralization.

Mixed-species afforestation stimulates the flow and turnover of carbon and nitrogen within soil aggregates in a degraded karst ecosystem.

Phosphorus (P) availability is severely limited in alkaline calcareous soils due to fixation with calcium and magnesium, which restricts its uptake by crops such as maize. Rock phosphate (RP) is an affordable, eco-friendly P source, but its slow dissolution restricts its use in such soils. We hypothesized that pre-treating RP through co-composting with farmyard manure (FYM) and phosphate-solubilizing bacteria (PSB) could enhance P availability, soil fertility, and maize productivity. FYM was composted with RP and single superphosphate (SSP), with or without PSB, for 60 days, then applied to maize (Azam cultivar) at 90kg P₂O₅ ha⁻¹ in a randomized complete block design conducted at an agronomic research farm of University of Agriculture Peshawar Khyber Pakhtunkhwa Pakistan in 2023. The FYM + RP+PSB compost produced the highest plant height (136.4cm), grain yield (3427kg ha- 1) and biomass (9783kg ha- 1), all exceeding those of SSP alone ( p < 0.05). Plant P uptake (19.6kg ha- 1) and post-harvest soil available P (3.76mg kg- 1) was higher under FYM + RP+PSB compost indicating enhanced soil fertility. Phosphorus use efficiency of RP increased significantly (p < 0.05) from 4.24% (sole RP) to 13.24% (FYM + RP) and 23.15% (FYM + RP+PSB). These findings suggest that co-composting RP with FYM and PSB is a cost-effective and sustainable strategy to improve P availability and maize productivity in calcareous soils, reducing dependency on chemical P fertilizers.

Onion (Allium cepa L.) production in hyper-arid environments is constrained by poor soil fertility, limited water availability, and post-harvest losses that reduce market viability. The interactive effects of foliar application of copper oxide (CuO) and calcium oxide (CaO) nanoparticles (NPs), combined with sugarcane filter mud cake (FMC), on onion growth and storage quality in calcareous hyper-arid soils remain to be characterized. A two-season field study (2023/24-2024/25) evaluated the effects of FMC (30 t ha⁻¹) combined with foliar CuO NPs (10, 20, and 30mg L⁻¹) and CaO NPs (50, 100, and 150mg L⁻¹), applied singly and in combination, on onion cv. Sabeeni in Upper Egypt. Vegetative growth, yield traits, nutrient uptake, and storage performance were quantified. Organic fertilization and nanoparticle treatments interacted significantly: yields of 42-45 t ha⁻¹ (15-21% above control) were achieved with low-to-moderate CuO NPs (10-20mg L⁻¹) and high CaO NPs (150mg L⁻¹); high CaO NPs alone maintained yields close to control values (< 3% increase); and excessive CuO NPs (30mg L⁻¹) with insufficient Ca was associated with phytotoxicity and yield reductions (21.29-28.90 t ha⁻¹). Tissue Cu concentrations ranged from 6.17 to 39.33mg kg⁻¹ and Ca from 2,556 to 4,750mg kg⁻¹. These results suggest that combining organic amendment with appropriately balanced nanoparticle nutrition may represent a scalable approach to improving onion yield by 15-21% and extending post-harvest shelf life under hyper-arid conditions.

Phosphorus (P) deficiency is a major factor limiting crop productivity in many soils worldwide. This study aimed to investigate the potential of seed priming with monopotassium phosphate (200 mmol L-1) to alleviate the adverse effects of P deficiency in Chenopodium quinoa Willd. Seedlings issued from unprimed and primed seeds were cultivated in plastic pots filled with inert sand under P deficient or P sufficient conditions. In plants from unprimed seeds, P deficiency decreased shoot and root growth, leaf P and potassium ion (K+) content, leaf water content, gas-exchange performance, and photosynthetic pigment concentrations, while increasing lipid peroxidation and leaf acid phosphatase activity. Interestingly, monopotassium phosphate (KH2PO4) seed priming alleviated P deficiency stress in quinoa, resulting in significant improvement in shoot (9.9-fold) and root (8.1-fold) growth, as well as photosynthetic activity (five-fold and four-fold increases in net assimilation rate (A) and stomatal conductance (gs), respectively). Chlorophyll content increased four-fold, while carotenoids content increased by 70%, together with an overall improvement in plant nutritional status. This beneficial effect was associated with lower levels of leaf malondialdehyde. However, no significant differences were observed in leaf osmotic potential, anthocyanin content, or acid phosphatase activity between plants derived from primed and unprimed seeds. KH2PO4 seed priming enhances quinoa tolerance to P deficiency through improved photosynthetic integrity, root growth, nutritional status, and strengthened antioxidant defence. Hence, KH2PO4 seed priming appears to be a promising strategy for improving quinoa productivity in calcareous soils. © 2026 Society of Chemical Industry.

PurposeSalinity severelyconstrains viticulture in calcareous soils by disrupting rhizosphere microbial community, nutrient availability, and physio-biochemical homeostasis, thereby reducing fruit yield. This study aimed to (i) assess the effects of soil-applied citric acid (CA) and halotolerant/halophilic citrate-utilizing plant growth-promoting rhizobacteria (CU-PGPR; Bacillus spizizenii and Halomonas marinus) on the microbial community and chemical properties of saline-calcareous soil, (ii) evaluate vine physio-biochemical responses to the individual and combined treatments, and (iii) determine their impacts on yield and fruit quality.MethodsA 2-field experiment (2023/2024 and 2024/2025) on Vitis vinifera at the Faculty of Agriculture’s Experimental Farm (32°42′ N, 29°75′ E), Fayoum University, Egypt. This study evaluated three CA rates: 0 (CA0), 100 (CA100), and 200 (CA200) g vine⁻¹ season⁻¹ and three inoculation treatments: non-inoculated (NI), H. marinus, or B. spizizenii. Measurements included rhizospheric bacterial counts, soil chemistry (pH, electrical conductivity; ECe, and macro- and micro-nutrient availability), leaf and petiole nutrients, physio-biochemical traits, yield, and fruit quality.ResultsCo-application of CA200 × B. spizizenii exhibited the strongest synergistic effects. Total bacterial count and specific functional groups markedly increased. Soil pH declined by 6.1%, while available N, K⁺, Fe²⁺, and Zn²⁺ increased by 817%, 105%, 659%, and 720%, respectively. The CA200 × H. marinus resulted in the highest available P (310% above CA0 × NI), though ECe was unaffected. Enhanced nutrient bioavailability improved ionic balance, raising the leaf K⁺/Na⁺ ratio by 78% and the Ca²⁺/Na⁺ ratio by 74.7%, while reducing Na⁺ by 31% compared with CA0 × NI. Physio-biochemically, CA200 × B. spizizenii boosted vine water content, osmotic adjustment, antioxidant capacity, and photosynthetic efficiency over CA0 × NI. Consequently, grape yield, pruning weight, fruit TSS/acid ratio, and firmness increased by 97%, 81%, 99%, and 24%, respectively, averaged across both seasons, over CA0 × NI.ConclusionCo-application of 200 g CA vine− 1 season⁻¹ with B. spizizenii inoculation effectively revitalizes microbial activity and enhances nutrient bioavailability, offering a promising strategy for sustaining viticulture under saline-calcareous soil conditions.Graphical

Soil pH is an influential abiotic environmental factor. Here, we identify responses to central stimuli associated with calcareous alkaline soils in Arabidopsis and comparatively explore the potential of the closely related Arabidopsis halleri for addressing how plants cope with local soil pH. We profiled the root transcriptome upon applying a set of hydroponic treatments-low bioavailable iron (Fe), alkaline pH and both in combination. Among the known Fe deficiency responses (ferrome), pervasively Fe-deficiency responsive transcripts (pIDR) encoding the transcription factor PYE and its targets responded co-directionally to Fe deficiency also at pH 7.5. A distinct subgroup of additionally alkaline-pH-responsive transcripts (aAPRs), comprising FIT and FIT-dependent genes, showed a co-directional response to pH 7.5 even with available Fe. Root hair densities in both species increased at an alkaline pH. Compared with A. thaliana, A. halleri accessions from soils of contrasting pH showed elevated tolerance to low-Fe and alkaline pH based on chlorophyll content and root growth. A. halleri from high-pH soils convergently exhibited longer and less branched root systems, more stable ionomes across conditions, and attenuated root growth at alkaline pH with Fe. Our findings provide insights into Fe-deficiency regulatory networks and identify soil pH-related phenotypic divergence within A. halleri and across species.

ABSTRACT The aim of the present study was to evaluate the interactive effects of various biochar sources (sheep manure, rice husk, and municipal solid waste, applied at 3% (w/w)) and Si application rates (200 and 400 mg Si kg−1 soil) on grain yield, nutrient composition of triticale (X Triticosecale Wittmack), and the chemical properties of Pb-contaminated calcareous soil in a greenhouse trial. Among the biochars tested, sheep manure biochar was the most effective at reducing soil available Pb concentration (16.6% reduction), likely because of its high pH, phosphorus, and soluble salt content. The highest Si application rate (400 mg Si kg−1) also significantly reduced soil available Pb concentration by 6.6%. However, the most effective treatment for enhancing triticale grain yield (68% increase) and reducing grain Pb concentration (54% reduction) compared to the control was the combined application of sheep manure biochar and the lower Si level (200 mg Si kg−1). At the higher Si application rate (400 mg Si kg−1), both grain yield and macro- and micronutrient uptake were markedly suppressed, potentially due to nutrient antagonisms associated with sodium metasilicate. These results underscore the synergistic effects of sheep manure biochar and moderate Si application in immobilizing soil Pb, enhancing triticale nutrient uptake, and improving grain yield in Pb-contaminated calcareous soils. The study recommends further investigations into using other silicon compounds, such as calcium and potassium silicates, and biochars produced at varying pyrolysis temperatures, to assess their potential in mitigating the adverse effects of Pb on triticale growth in calcareous soils.

Iron (Fe) deficiency in food crops, particularly on calcareous soils, limits productivity and human nutrition. This study investigated two common bean (Phaseolus vulgaris) genotypes, Guaymí (high Fe-accumulating, HI) and Matambú (low Fe-accumulating, LI) to understand physiological and genetic mechanisms underlying Fe uptake, shoot accumulation, and adaptation under low and adequate Fe conditions. Plants were grown under controlled Fe-deficient and Fe-sufficient conditions. Root-induced acidification, ferric reductase activity, leaf chlorosis, and Fe and Mn accumulation were measured. Gene expression of Fe-related transporters and mobilisation pathways was assessed at early and prolonged stages of deficiency. Under Fe deficiency, HI showed stronger root acidification, higher ferric reductase activity, and greater Fe uptake compared with LI. HI maintained growth, leaf Fe, and Mn content, whereas LI relied on polyphenol-based Fe mobilisation. Early-stage Fe-related gene expression differed between the two genotypes but converged under prolonged deficiency. The HI genotype demonstrates superior Fe absorption efficiency and adaptive responses under Fe-limited conditions, sustaining growth and Fe accumulation in roots and shoots. These findings highlight the potential of selecting or engineering Fe-efficient cultivars to improve crop productivity and nutritional quality, offering a promising strategy to address Fe deficiency in agriculture and human diets.

Drip irrigation and integrated amendments drive soil–crop system improvements in calcareous soils

The mechanical response of cemented calcareous soils to water immersion is critically influenced by the complex architecture of their particulate framework and cementing materials. Understanding the mechanical and hydrochemical properties of these soils under saturated conditions is crucial for assessing the stability of geoengineering structures. The research detailed in this manuscript evaluates the influences of water immersion on the mechanical and hydrochemical characteristics of cemented calcareous soil collected near the Jinsha River. Additionally, the study discusses the implications of these soil properties for geological phenomena located in proximity to the sampling area. The results showed that prolonged immersion precipitates substantial alterations in the hydraulic conductivity of cemented calcareous soil, accompanied by extensive ion dissolution that modifies its hydrochemical properties. The soaking solution exhibits alkalinity with high concentrations of Ca 2+ and HCO 3 − . Initial short-term immersion augments the strength of cemented calcareous soil, while a progressive decline in strength occurs as the immersion period extends, with the natural state displaying markedly greater strength relative to the dried state. Long-term immersion facilitates the moisture infiltration into the interstitial spaces between particles, dissolving the cementing material and undermining the interparticle bonds, which critically impairs the mechanical properties and stability of the soil. Furthermore, localized seepage facilitates the migration and precipitation of soluble salts in moisture-prone environments, exacerbating the weathering and degradation processes. Such long-term immersion results in structural transformations within the soil, undermining the cementation structure and potentially precipitating soil collapse.

Reducing cadmium bioavailability in soil with micronutrient sulfates: Insights from duodenal transporter expression and intestinal microbiota in a mouse model.

Soil type-dependent effects of earthworm activity on antimony bioavailability in Chinese agricultural soils.

ABSTRACTThis study evaluated the effects of trunk and root injections of iron (Fe), zinc (Zn), and calcium (Ca) on fruit characteristics and leaf mineral composition of “Mazafati” date palm (Phoenix dactylifera L. cv. “Mazafati”) under orchard conditions in Kerman Province, Iran. A randomized complete block design with nine treatments was applied to 15‐year‐old palms: trunk injection of ferrous sulfate (25, 75, 150 g L−1), root injection of ferrous sulfate (75 g L−1), trunk injection of zinc aminochelate (2, 4 g L−1), trunk injection of calcium aminochelate (3, 5 mL L−1), and an untreated control (n = 3 replications). Fruit physical traits and leaf mineral concentrations were measured at the rutab stage and ~100 days post‐injection, respectively. Data were analyzed using ANOVA, Pearson correlation, and stepwise regression. Trunk injection of Fe at 150 g L−1 maximized flesh weight (16.38 g) and seed weight (1.31 g), while Zn at 4 g L−1 yielded the highest total fruit weight (17.59 g). Fe injection significantly increased leaf Fe, Mg, and Ca concentrations; Zn injection elevated leaf Zn and K but reduced Fe and Mg. Pearson correlations revealed positive Fe–Mg (r = 0.42) and Fe–Ca (r = 0.38) associations, and negative Zn–Mg (r = −0.41) and Zn–Fe (r = −0.30) interactions. Stepwise regression identified fruit flesh weight and leaf P as the strongest predictors of fruit weight (R2 = 82.1%, p ≤ 0.01). Trunk injection of Fe (150 g L−1) and Zn (4 g L−1) at optimized dosages significantly improved key fruit traits and leaf mineral status in “Mazafati” date palm. However, observed nutrient antagonisms (e.g., Zn–Fe, Zn–Mg) underscore the need for balanced fertilization strategies. This approach shows promise for enhancing productivity in calcareous soils where conventional uptake is limited, though multi‐season trials and economic analyses are recommended before wide‐scale adoption.

Cadmium (Cd) is a toxic heavy metal released through various industrial processes, mining, batteries disposal and agro-chemicals application posing serious risks to agricultural production and food safety. Limited research has investigated the potential of organic chelators, such as ascorbic acid (AsA) and citric acid (CA), to mitigate Cd toxicity and reduce its bioaccumulation in plants. Current pot study was conducted to evaluate the effects of Cd stress on two spinach varieties, i.e., Green Gold (Hybrid) and AARI Desi (Conventional), grown in sandy clay loam soil, and assessed the efficacy of foliar-applied AsA, CA, and their combination in alleviating Cd-induced stress. Stress was applied by irrigating the crop with Cd-contaminated water (1mg L-1) whereas organic acids, AsA and CA, were applied at 10mM concentration as individual treatments and 5mM + 5mM as combined treatment. Cd stress significantly reduced root and shoot growth, physiological attributes, and biochemical parameters, while enhancing antioxidant enzyme activity and Cd accumulation in both varieties. Foliar applications of AsA, CA, and particularly combined application significantly improved plant growth and biomass, chlorophyll concentration, and biochemical traits, while markedly reducing Cd uptake in roots and leaves. The combined application of AsA and CA reduced the Cd concentration in shoots by 36% and in roots by 40% and increased shoot dry weight up to 43% and root dry weight up to 50% compared to cadmium stressed plants. Overall, the study demonstrates that AsA, either individually or in combination with CA, enhances the antioxidant defense and promotes metal chelation, thereby reducing oxidative damage and Cd bioaccumulation. This ultimately leads to improved growth and physiological performance of spinach under Cd stress.

Phosphorus fixation represents a primary constraint limiting the agronomic efficiency of phosphate fertilizers in calcareous soil. Rapeseed roots secrete amounts of organic matter, which can mobilize and decompose insoluble phosphorus in the soil. However, the activation mechanism of sparingly insoluble phosphorus in calcareous soils by rapeseed rhizosphere microorganisms remains unclear. This study aimed to screen and identify phosphate-solubilizing microorganisms from the rapeseed rhizosphere of calcareous soil, and to elucidate their key metabolic pathways for activating insoluble phosphorus. The results demonstrated that (i) fourteen dominant phosphate-solubilizing strains were isolated from rapeseed rhizosphere soil. Among these, Advenella alkanexedens was verified to significantly promote wheat growth and increase soil available phosphorus content. (ii) The culture condition optimization and functional characterization for Advenella alkanexedens revealed that its optimal growth temperature was 30°C, with an initial pH of 7. Its phosphate-solubilizing ability was regulated by Mg2+, K2+, and Ca2+ ions, and the strain exhibited considerable salt tolerance and the ability to produce siderophores. (iii) Advenella alkanexedens increased soil available phosphorus content by 11.49%-81.91% and elevated phytase activity by 36.87%-82.49%. Correlation analysis indicated that soil available phosphorus and phytase activity were significantly positively correlated with Ca2-P, Ca8-P, and Al-P fractions. (iv) Amino acids and organic acids were identified as the key metabolites influencing the phosphate-solubilizing function of Advenella alkanexedens. The KEGG pathway analysis showed these metabolites were primarily enriched in β-alanine metabolism and arginine and proline metabolism pathways. Our findings confirm that Advenella alkanexedens not only promotes crop growth but also significantly increases labile P fractions (Ca2-P, Ca8-P, Al-P) while reducing more stable forms (Ca10-P), thereby enhancing soil phosphorus use efficiency. This study holds important implications for planting rapeseed to activate insoluble phosphorus in soil, to reduce phosphate fertilizer application, and to promote sustainable utilization of soil phosphorus resources. Furthermore, it provides a theoretical foundation for developing agricultural microbial inoculants.IMPORTANCEOur results confirm that Advenella alkanexedens not only benefits crop growth but also converts insoluble phosphates (O-P, Ca10-P) into highly active inorganic phosphorus components, thereby enhancing the utilization efficiency of soil phosphorus. This study was of great significance in activating the insoluble phosphorus in the soil, reducing the input of phosphate fertilizers, achieving the sustainable utilization of phosphorus resources, and protecting the environment. Additionally, it provided a basis for developing agricultural microbial agents.

This study examines whether bulk soil nutrient pools reliably reflect leaf nutrient status in olive orchards under alkaline, calcareous conditions, where carbonate buffering is known to constrain nutrient availability. We evaluated soil-leaf nutrient relationships in 25 rainfed olive orchards ('Kilis Yaglik') in southeastern Türkiye over two consecutive years (2017-2018). Soils remained strongly alkaline and highly calcareous, while organic matter declined by approximately 35% between years. Leaf nutrient composition did not consistently track soil nutrient dynamics. While some soil nutrients exhibited interannual variation, corresponding leaf responses were element-specific and not uniformly aligned with soil changes. Correlation and principal component analyses revealed variable and year-dependent associations between soil and leaf nutrients, with no reproducible, strong soil-leaf relationships across years. These findings indicate that, under carbonate-buffered conditions, bulk soil nutrient pools are not reliable predictors of canopy nutrient status. Instead, leaf nutrient composition appears to reflect integrated and element-specific availability patterns rather than direct soil-plant coupling.

Soil salinity severely constrains maize productivity, especially in arid and semi-arid regions with calcareous and salt-affected soils. Conventional strategies often fail to restore soil health and sustainably enhance crop resilience. Although biochar, vermicompost and silicon individually alleviate salinity stress, their integrated use under naturally saline field conditions remains underexplored. This study evaluated whether their combined application could synergistically improve maize performance by enhancing ionic homeostasis, antioxidant defense and water and nutrient status. A field trial was conducted on naturally saline soil (EC = 9.6 dS m-1; pH = 8.2; sandy loam) using salt-tolerant (Dekalb-8148) and salt-sensitive (S-626) maize genotypes. Treatments included: control, 60 t ha-1 biochar (6% w/w), 50 t ha-1 vermicompost (5% w/w), 100kgha-1 silicon (as calcium silicate) and their combinations. Co-application significantly improved root/shoot biomass, leaf area (by 125.7% in Dekalb-8148 and 81.3% in S-626) and photosynthetic efficiency (higher SPAD values). These gains were mechanistically linked to enhanced relative water content (27.9-81.5%), membrane stability (23.5-48.2%) and K+/Na+ ratios (36.6% and 69.0%, respectively). Antioxidant enzyme activities (SOD, POD, CAT and APX) markedly increased, especially in S-626, indicating superior oxidative stress mitigation. There was also a significant increase in the yield components (cob length, 100-grain weight and grain yield per cob), where S-626 showed a greater relative response. Principal component and correlation analyses supported the close association between growth, physiological, biochemical and yield characteristics. The results showed that organic and inorganic amendments complemented each other in reducing the effects of salinity in agroecosystems and this effect offers a viable and sustainable solution for improving the tolerance of maize and facilitating genotype-specific control of salt agroecosystems.

ABSTRACT Phosphorus (P) availability in calcareous soils is limited due to high calcium carbonate content, promoting P fixation and reducing plant uptake. Silicon (Si) has the potential to improve P availability and uptake. This study evaluates the influence of Si on P availability, soil mineralogy, and plant uptake in calcareous soils using a dual-scale experimental approach. The study comprised a 180-day incubation experiment and greenhouse pot trials with wheat. The incubation study examined temporal dynamics of available P under varying P (0(P0), 8.4(P1), 16.8(P2) and 25.2(P3) mg/kg) and Si (0(Si0), 100(Si1), 200(Si2), 400(Si3) and 800(Si4) mg/kg) doses. Greenhouse experiments assessed plant P uptake and bioavailability effects of Si. Soil and plant samples were analyzed for extractable Si, available P, and plant P content, while mineralogical changes were examined using X-ray diffraction (XRD). The results revealed a significant PxSi interaction. Higher Si doses consistently increased soil available P, especially at elevated P rates. The P3Si4 treatment yielded the highest available P (34.67 mg/kg) and plant P uptake. Si application contributed to maintaining available P levels over time, indicating improved P-use efficiency. XRD analysis indicated that Si application was associated with changes in relative mineral peak intensities, including a reduced prominence of clay-related reflections and enhanced carbonate-silicate signals, suggesting a mineralogical environment less favorable for strong P fixation. The findings demonstrate the synergistic potential of Si and P in improving P availability and uptake in calcareous soils. Silicon application emerges as a promising strategy to enhance fertilizer efficiency and sustainable crop production.