Integrated Bentonite, Humic Substances and Bacillus polymyxa Enhance Soil Functionality, Rhizosphere Processes, Nutrient Uptake and Fruit Quality of Siwi Date Palm Under Deficit Irrigation in Sandy Soil
Arid sandy soils are characterized by poor water retention, low nutrient availability, and limited productivity, posing major constraints to sustainable date palm cultivation under increasing water scarcity. A three-year field experiment was conducted to evaluate the combined effects of bentonite (BN), humic substances (HS), and Bacillus polymyxa (BP) under three irrigation regimes (70, 85, and 100% of crop evapotranspiration (ETc)) on soil hydro-physical properties, nutrient uptake, and fruit quality of ‘Siwi’ date palm (Phoenix dactylifera L.). Twelve treatment combinations (3 irrigation regimes × 4 soil amendment treatments) were evaluated over three consecutive growing seasons. The integrated application of BN, HS, and BP significantly improved soil hydro-physical properties by increasing field capacity and plant-available water while reducing bulk density. These improvements were associated with enhanced leaf N, P, and K concentrations and greater accumulation of total soluble solids, total and reducing sugars, phenolic compounds, flavonoids, and β-carotene compared with the untreated control. The combined application of BN (12 kg palm−1) + HS (1 L palm−1) + BP (28 mL palm−1) produced the most favorable overall responses. Moderate deficit irrigation (85% ETc) provided the best balance between fruit quality and water conservation, maintaining superior fruit biochemical quality while reducing irrigation water use by approximately 15% compared with full irrigation. Multivariate analyses further supported these findings by revealing strong positive associations among soil water availability, nutrient status, sugars, and antioxidant-related compounds, while climatic variables were closely associated with seasonal variation in fruit biochemical characteristics. Overall, the integrated application of bentonite, humic substances, and B. polymyxa under 85% ETc irrigation represents an effective management strategy for improving soil performance, enhancing fruit nutritional quality, and increasing water-use irrigation efficiency in sandy soils under arid conditions.
Sandy soils are characterized by low organic matter content, weak nutrient retention, and limited water-holding capacity, which restrict crop productivity in arid and semi-arid regions. This study evaluated the individual and combined effects of biochar, Azolla pinnata, and eggshell powder on soil properties and the productivity of common bean (Phaseolus vulgaris L.) grown in sandy soil. Field experiments were conducted during two consecutive growing seasons (2021–2022) at the Ismailia Agricultural Research Station, Egypt, using a randomized complete block design with eight treatments and three replicates. Soil chemical properties, photosynthetic pigments, vegetative growth, biomass accumulation, and yield parameters were evaluated. The combined application of biochar, Azolla, and eggshell powder significantly improved soil fertility compared with the control treatment. Soil organic matter increased to 0.70%, while available nitrogen, phosphorus, and potassium reached 51.10, 6.67, and 200 mg kg⁻¹, respectively. The integrated treatment also enhanced chlorophyll content, plant growth, biomass production, and seed yield across both seasons. Correlation analysis indicated strong positive relationships between soil organic matter, nutrient availability, and crop productivity. These results demonstrate that the integrated application of biochar, Azolla pinnata, and eggshell powder can effectively improve soil fertility and enhance the productivity of Phaseolus vulgaris in sandy soil systems.
D. M. Khalifa, A. Alrashidi, Ammar Al-Farga et al.· Scientific Reports· 0 citations
Although green manure crops are widely recognized for ameliorating alkaline soils, some previous studies have focused mainly on laboratory germination screenings or single yield indicators, and field validation of the synergy between high yield and soil improvement remains comparatively limited. This study evaluated 16 species/accessions with varying salt tolerance in a typical alkaline soil (initial pH 9.01, EC 306 μS·cm−1) in Heilongjiang Province during 2024–2025, based on prior laboratory screening. The experiment was conducted at a single location with three field replicates, and the same plots were monitored across both years. Plant height, fresh/dry grass yield, and soil properties (pH, EC, organic matter, nutrients) were monitored. Glycine max (L.) Merr. and Sesbania Scop. achieved dual synergy, with two-year average fresh yields of 40,733 and 35,750 kg·ha−1, respectively, while reducing soil pH by 0.28–0.29 and electrical conductivity (EC) by 42.2–46.3%. Melilotus officinalis and Vicia villosa Roth exhibited the strongest alkali reduction (pH ↓0.29, EC ↓39.0–39.7%) with moderate yields. Sorghum sudanense showed the highest salt reduction (EC ↓49.0%). Principal component analysis classified the 16 species into four functional types, revealing preliminary ecological patterns for functional differentiation. This study proposes a “laboratory screening–field validation–functional classification” evaluation framework, which requires further validation across different regions and longer time scales for the biological amelioration of alkaline soils.
Ruonan Du, Qiang Gao, Xue Yang et al.· Agronomy· 0 citations
Sandy soils are widely distributed in Egypt and are characterized by poor physical properties and a limited capacity to retain irrigation water and nutrients, which severely constrains agricultural productivity. Addressing these limitations has become increasingly critical to ensure sustainable crop production under arid and semi-arid conditions. Therefore, this study aimed to evaluate the effectiveness of biochar as a soil amendment for improving growth performance, yield, nutrient accumulation, photosynthetic pigments, and essential oil production of Mentha spicata cultivated under sandy soil conditions over two successive seasons (2024–2025). The field experiment consisted of four treatments: untreated control, NPK at 5 g L-1, biochar at 12.5 ton ha-1, and combined NPK (5 g L-1) and biochar (12.5 ton ha-1). The results showed that biochar application, either alone or in combination with mineral fertilizer, significantly improved all vegetative growth parameters, fresh and dry herbage yields, essential oil percentage and yield, leaf macronutrient content (N, P, and K), and chlorophyll b concentration. Biochar applied alone consistently outperformed mineral fertilizer alone, while the combined biochar–NPK treatment produced the highest values for all measured traits, with improvements exceeding the additive effects of individual applications. These enhancements were closely associated with increased nutrient accumulation and improved nutrient use efficiency, reflecting the ability of biochar to retain nutrients, reduce leaching losses, and synchronize nutrient availability with plant demand. The synergistic interaction between biochar and mineral fertilization highlights the potential of biochar as a sustainable soil amendment for improving productivity, quality, and resource-use efficiency of mint grown in low-fertility sandy soils.
Y. Soliman, W. Soliman· Scientific Reports· 0 citations
Low soil fertility and restricted nutrient bioavailability are critical limiting factors for sustainable vegetable production, particularly in marginal sandy soils. This study addressed these challenges by investigating the efficacy of a novel sugarcane-derived molasses treated (SOFA) as a soil conditioner and nutrient source for eggplant (Solanum melongena L.), a crop for which comprehensive studies on such integrated approaches in these soil types are limited. Field experiments were conducted over two consecutive growing seasons to evaluate the impact of SOFA, applied either independently or in combination with mineral nitrogen (N), on soil physicochemical properties and crop performance.The study results demonstrated that integrated fertilization significantly improved soil physicochemical properties and crop performance. The treatment T3 (50% mineral N + 50% SOFA) achieved the highest total fruit yield (8.84 kg plant−1), representing a 111% increase compared to the control (4.18 kg plant−1). Similarly, T2 (75% N + 25% SOFA) significantly enhanced vegetative growth, chlorophyll content, and fruit nutritional quality. Soil organic matter increased by up to 56%, while available nitrogen, phosphorus, and potassium increased by up to 240%, 209%, and 67%, respectively, compared to the control. Moreover, SOFA application contributed to moderating soil alkalinity and improving nutrient availability, despite slight increases in electrical conductivity at higher application rates. Eggplant fruit quality traits were also significantly improved, with total soluble solids (TSS) increasing by 42% and anthocyanin content by 49% under optimized treatments. Economic analysis revealed that T2 and T3 achieved the highest profitability, with investment factors approaching 5.0, indicating superior economic efficiency. These findings highlight the potential of treated molasses-based amendments (SOFA) as a sustainable strategy for restoring marginal sandy soils and optimizing the productivity and nutritional quality of S. melongena.
Abdel-Haleem A. H. El-Shaieny, Ahmed N. Gad El Rab, H. Farrag et al.· Scientific Reports· 0 citations
In semi‐arid Mediterranean conditions, irrigation management is constrained by soil degradation and water scarcity. This exploratory study assessed, over two consecutive growing seasons (2022–2023) in the Mitidja plain, Algeria, the synergistic effects of organic mulches (wood chips, sawdust, wheat straw and a composite mixture) combined with drip irrigation on the soil properties, growth and yield of tomato. Due to the absence of true replication, the results are presented as descriptive statistics and should be interpreted as presented trends rather than statistically validated effects. The findings suggest that the composite mulch (P4A) corresponded to higher water retention, more moderate pH, more stable soil temperature and electrical conductivity, and better plant growth. P4A showed an increase in soil organic matter to 2.6% (from 1.3% in 2022) and was accompanied by water savings of 27% (first season) to 50% (second season). The yield reached 15.1 t ha
−1
in 2023 under P4A, compared to 4.5 t ha
−1
for the control, and the water productivity (WP) increased from 1.6 to 9.8 kg·m
−3
. This research suggests that composite organic mulch generates cumulative benefits for soil water, temperature, nutrient availability and productivity, offering a potential low‐cost strategy for water savings and soil quality improvement under semi‐arid conditions.
Sustainable crop residue management in alkaline agroecosystems is challenging due to trade-offs among carbon stabilization, nutrient availability, and microbial activity. To identify an optimal upcycling strategy for compacted alkaline farmland, a two-year wheat–maize rotation experiment in the Yellow River floodplain compared four treatments: no organic amendment (CK), direct straw return (CS), straw-derived biochar (CB), and straw-derived synthetic humic acid (CH). Results showed that CH produced the most balanced improvements across all dimensions. Compared to CK (pH 8.62) and CB (pH 9.16), CH significantly reduced soil pH to 8.03, enhancing alkaline buffering. CH achieved the highest available phosphorus (2.36 mg kg−1), macroaggregate proportion (19.40%), and microbial biomass carbon (91.77 mg kg−1). Enhanced humification was evidenced by superior HA content (5.82 mg kg−1) and an HA/FA ratio of 1.90 in the 0–20 cm layer. Agronomically, CH achieved the highest annual grain production (ATGP, 12.11 × 103 kg ha−1, comprising 5.65 × 103 kg ha−1 for wheat and 6.46 × 103 kg ha−1 for maize) and maximum Integrated Sustainability Score (ISS = 1.000). These findings suggest that converting straw into synthetic humic acid effectively bridges the gap between unstable raw residues and inert biochar, serving as a promising alternative pathway for improving soil structure, nutrient availability, and productivity in compacted, alkaline floodplain farmland.
