Application Of Soil Amendments Research Articles

Role of different organic and inorganic amendments in the biofortification of iodine in Coriandrum sativum crop

Iodine deficiency disorder (IDDs) is one of the most prevailing and common health issues in mountainous communities. An effective way to control the prevalence and emergence of IDDs in remote areas is to use iodized salt. However, recent studies indicated that iodized salt is mostly lost during the cooking process. The current study of iodine biofortification differed from the previous studies in two main aspects: it involved exogenous organic iodine (OI), and inorganic iodine such as potassium iodide (KI), added in the amended soils, which previous studies did not consider. Moreover, the translocation, transformation, and distribution of iodine from soil to plants are poorly understood in amended soil. Thus, identifying an effective management option to enhance iodine (I) bioavailability in nutrient-deficient soils is currently a significant challenge. Therefore, a greenhouse study was conducted to investigate the effects of organic and inorganic soil amendments on the uptake of different iodine sources in coriander crops. Results showed that applying an inorganic iodine source significantly enhanced the iodine edible part of the crop compared to the control (p < 0.05). The application of soil amendments relatively improved iodine uptake by the coriander crop compared to the control. The highest iodine was found in crop tissues grown in wood ash-amended soil supplemented with KI (291.97 μg kg−1). The KI uptake was significantly higher than the OI (p < 0.05). Compared to OI, a higher translocation factor (0.96) and distribution coefficient (3.51) were found for plants treated with KI. Thus, this study indicates that a suitable soil amendment can be a better option for iodine biofortification and that it can serve as an alternative to iodized salt in preventing IDDs.

Soil amendments for vanadium remediation: a review of remediation of vanadium in soil through chemical stabilization and bioremediation.

Immobilization of vanadium (V) in soils is one option to prevent groundwater contamination and plant uptake. Phytoremediation, microbial remediation, and chemical stabilization using soil amendments are among the leading environmentally friendly and economically feasible techniques in V remediation. Soil amendments were used to reduce V mobility by immobilizing it in the soil matrix through chemical stabilization, while bioremediation methods such as phytoremediation and microbial remediation were used to remove V from contaminated soils. Vanadium exists in several species and among them V5+ species are the most prevalent, toxic, and soluble form and present as a negatively charged ion (H2VO4- and HVO42-) in oxic soils above pH 4. Amendments used for chemical stabilization can change the physicochemical properties enhancing immobility of V in soil. The pH of the soil environment, point of zero charge of the colloid surface, and redox conditions are some of the most important factors that determine the efficiency of the amendment. Commonly used amendments for chemical stabilization include biochar, zeolites, organic acids, various clay minerals and oxides of elements such as iron, titanium, manganese, and aluminum. For bioremediation, chelating agents and microbial communities are used to mobilize V to enhance phyto-or microbial-extraction procedures. The objectives of this review were to discuss remediation methods of V while considering V speciation and toxicity in soil, and soil amendment application for V removal from soil. The information compiled in this review can guide further research on soil amendments for optimal V remediation in largely contaminated industrial sites.

Nitrogen fertilizer promoting salt tolerance of two sorghum varieties under different salt compositions

Soil salinization is more aggravating than ever before and techniques are needed to mitigate this problem; understanding salinity-fertilizer relationship is of considerable economic importance for promoting crop growth and productivity in saline soil. A pot experiment was done in a greenhouse to determine whether the N could alleviate the negative effect of different salts compositions on the growth, and physiological attributes of the two most used Sudan sorghum (Sorghum bicolor (L.) Moench) cultivars (Wadahmed and Tabat). The plant was subjected to the salt stress at 0, 0.3419 M NaCl, and 0.1408 M Na2SO4, and four levels of N application 0, 4, 8, and 12 g N kg-1 soil, designated as N0, N1, N2, and N3, respectively. Results showed that Na2SO4 was reduced plant height, leaf area index, number of leaves, dry weight (DW), chlorophyll a, total chlorophyll content, and increased soluble protein content, activities of peroxidase (POD) and catalase (CAT) activities by 16.4%, 29.7%, 61.5%, 28.7%, 39.6%, 12.7%, 99.7%, 34.3%, 51.8%, respectively, when compared with the non-saline treatment. The Na2SO4 salt had a more harmful effect than NaCl. This study revealed that N fertilizer was successful for alleviating the adverse impacts of both types of salt. In this study, 12 g N kg-1 soil was most effective on most of the measured parameters of two sorghum cultivars. These findings demonstrated that the N soil amendment application could alleviate the harmful impact of salinity. ‘Wadahmed’ was more tolerant to salinity stress than ‘Tabat’ during the boot stage of sorghum plant.

The role of sulfur nutrition in plant response to metal(loid) stress: Facilitating biofortification and phytoremediation.

Metal(loid)s contamination poses a serious threat to ecosystem biosafety and human health. Phytoremediation is a cost-effective and eco-friendly technology with good public acceptance, although the process does require a significant amount of time for success. To enhance the phytoremediation efficiency, numerous approaches have been explored, including soil amendments application with chelators to facilitate remediation. Sulfur (S), a macronutrient for plant growth, plays vital roles in several metabolic pathways that can actively affect metal(loid)s phytoextraction, as well as attenuate metal(loid) toxicity. In this review, different forms of S-amendments (fertilizers) on uptake and translocation in plants upon exposure to various metal(loid) are evaluated. Possible mechanisms for S application alleviating metal(loid) toxicity are documented at the physiological, biochemical and molecular levels. Furthermore, this review highlights the crosstalk between S-assimilation and other biomolecules, such as phytohormones, polyamines and nitric oxide, which are also important for metal(loid) stress tolerance. Given the effectiveness and potential of S amendments on phytoremediation, future studies should focus on optimizing phytoremediation efficiency in long-term field studies and on investigating the appropriate S dose to maximize the food safety and ecosystem health.

Effects of Cover Crops and Soil Amendments on Soil CO2 Flux in a Mississippi Corn Cropping System on Upland Soil

Agroecosystems, accounting for more than one-third of arable land worldwide, play an essential role in the terrestrial carbon (C) cycle. The development of agricultural practices, which maximize soil C sequestration from the atmosphere, is receiving growing attention due to the recognition of agroecosystems’ great potential to serve as sinks of atmospheric carbon dioxide (CO2). In particular, cover crop and soil amendment applications are generating much interest in mitigating climate change and enhancing agricultural ecosystem services. The objective of this study was to evaluate the effects of winter cover crop and soil amendments, including broiler litter (BL), flue gas desulfurization (FGD) gypsum and lignite, on soil CO2 flux from cropping systems in southeastern USA, where related studies were limited. A field study was conducted from 2019 to 2021 in a Mississippi upland corn cropping system with measurements of soil CO2 flux, moisture and temperature during cash crop growing seasons. We observed high temporal variability in soil CO2 flux with flux peaks between late June and early July, which is likely due to the temporal changes in soil moisture. A significant increase in soil CO2 flux was found with BL application (p < 0.05). Co-application of FGD gypsum and lignite with BL-reduced soil CO2 flux by 15–23% but did not fully eliminate the rising effects. Significantly higher soil CO2 flux and lower soil temperature were observed from fields with cover crops than those without cover crops in the third year of this study (p < 0.05), which is likely attributed to the higher organic C content accumulated in soil with cover crops. Future research should assess year-round soil greenhouse gas fluxes in both cash crop and cover crop growing seasons using a high temporal resolution measurement scheme.

Co-Composted Chicken Litter Biochar Increases Soil Nutrient Availability and Yield of Oryza sativa L.

Intensified cultivation of rice has accelerated weathering of most tropical acid soils leading to significant loss of base cations. In most developing countries, rice yield is low and this results in its production being costly because productivity versus labor is low. The objectives of this study were to (i) enhance soil chemical properties, nutrient uptake, and grain yield of rice grown on a mineral tropical acid soil using agro-wastes; (ii) determine the agro-waste (chicken manure, cow dung, forest litter, and Leucaena) that has the potential to significantly increase rice yield; and (iii) determine the residual effects of the organic soil amendments produced from the agro-wastes on soil and rice productivity. The treatments used in this three-cycle field study were (i) soil without amendments (S0); (ii) prevailing recommended rates for fertilizers (NPK-Mg); (iii) biochar–forest litter compost (OSA1); (iv) biochar–chicken litter compost (OSA2); (v) biochar–cow dung compost (OSA3); (vi) biochar–Leucaena compost (OSA4); and (vii) biochar–Leucaena–chicken litter compost (OSA5). Standard procedures were used to determine the plants’ rice growth, grain yield, plant nutrient concentrations and uptake, and selected soil chemical properties. The use of organic soil amendments (OSA1 to OSA5) significantly improved the soil chemical properties, rice plant growth, nutrient uptake, and grain yield compared with the prevailing method of cultivating rice (NPK-Mg). The application of organic soil amendments reduced the use of inorganic N, P, K, MgO, and trace elements fertilizers up to 25%, 100%, 64%, 100%, and 100%, respectively. The organic soil amendments with Leucaena significantly increased rice grain yield of OSA5 at 11.17, 13.11, and 10.06 t ha−1 in the first, second, and third cropping cycles, respectively. The residual effect of the organic soil amendments also improved rice plant growth, nutrient uptake, and rice grain yield although these were slightly reduced as compared to those of the two previous cropping cycles, the afore-stated treatments were superior to the prevailing method of cultivating rice (NPK-Mg). Transforming agro-wastes into organic soil amendments can improve tropical mineral acid soils and rice productivity.

Carbon Amendments Shape the Bacterial Community Structure in Salinized Farmland Soil.

Practical, effective, and economically feasible salt reclamation and amelioration methods are in great demand in arid and semiarid areas. Energy amendments may be more appropriate than alternatives for improving salinized farmland soil because of their effects on soil microbes. We investigated the effects of biochar (Carbon) addition and desulfurization (noncarbon) on the soil bacterial community associated with Zea mays seedlings. Proteobacteria, Firmicutes, and Actinobacteriota were the dominant soil bacterial phyla. Biochar significantly increased soil bacterial biodiversity but desulfurization did not. The application of both amendments stimulated a soil bacterial community shift, and biochar amendments relieved selection pressure and increased the stochasticity of community assembly of bacterial communities. We concluded that biochar amendment can improve plant salt resistance by increasing the abundance of bacteria associated with photosynthetic processes and alter bacterial species involved in carbon cycle functions to reduce the toxicity of soil salinity to plants. IMPORTANCE Farmland application of soil amendments is a usual method to mitigate soil salinization. Most studies have concluded that soil properties can be improved by soil amendment, which indirectly affects the soil microbial community structures. In this study, we applied carbon and noncarbon soil amendments and analyzed the differences between them on the soil microbial community. We found that carbon soil amendment distinctly altered the soil microbial community. This finding provides key theoretical and technical support for using soil amendments in the future.

Evaluating fall application of soil amendments to mitigate phosphorus losses during spring snowmelt

The potential of soil amendments in reducing phosphorus (P) loss has been reported under simulated snowmelt, but not evaluated in the field, under snowmelt conditions. We examined the effectiveness of alum (Al2(SO4)3·18H2O), gypsum (CaSO4·2H2O), and Epsom salt (MgSO4·7H2O) in reducing P loss from two flood-prone agricultural fields (non-manured field with initial soil test P concentrations, STP, of 76 mg kg−1 and manured field with initial STP of 202 mg kg−1), during snowmelt on Canadian Prairies. Amendments were applied (2.5 Mg ha−1) in 2020 fall to four replicated plots (3 m × 1 m) with pre-installed runoff boxes (1.2 m × 0.9 m). In the 2021 spring, snowmelt water in each runoff box was pumped out, volume recorded for each sampling day, and analysed for dissolved reactive P (DRP). Snowmelt DRP concentrations was greater in manured soil (0.73 ± 0.23 mg L−1) with high STP, than in non-manured soil (0.28 ± 0.10 mg L−1.) with low STP, implying a greater risk of P loss to snowmelt runoff when STP is high. Cumulative snowmelt DRP loads in non-manured soil ranged from 3.1 to 3.8 mg (equivalent to 0.03–0.04 kg ha−1) and were not significantly different among treatments. In the control treatment of the manured soil, the cumulative snowmelt DRP load from runoff boxes was 20.8 mg (equivalent to 0.19 kg ha−1), while amended treatments had 42 to 68 % lower cumulative DRP load than control, with the difference being significant only in Epsom salt treatment. Cumulative snowmelt DRP load was significantly and positively correlated to cumulative snowmelt volume (R2 = 0.84 for each soil). This study shows the potential of fall application of soil amendments, particularly Epsom salt, to reduce P loss to snowmelt from soils with high STP.

Implementation of Supplementary Water Irrigation and Rice Husk for Climate Change Adaptation and Improving Soil Quality in Dry Land, Gunungkidul

Dry land in Gunungkidul is the land that depends on rainfall as the main water source to the crops. This research aimed to evaluate the implementation of supplementary water irrigation and rice husk for improving soil quality. The study conducted at dry land of Wonosari-Gunungkidul on June-Sept 2019. Experimental Design used Randomized Completely Block and replicated four times. The treatments were frequency of irrigation, namely F1 (1 times), F2 (2 times), F3 (3 times) a week, and application of soil amendment, namely: M1 (without mulch), M2 rice straw 4 ton.ha-1), M3 (rice husks 4 ton.ha-1), M4 (straw mulch + rice husk 4 ton.ha-1). The result of study showed that applying straw much and rice husk plus supplementary water irrigation two times a week was able to provide the highest corn production (7.46 ton.ha-1) and was not significantly different to the irrigation three times a week and showed an increased yield of corn 52.56% compared to control (watering once a week and without mulch/rice husk). Applying straw and rice husk can be improved the chemical soil properties (increasing water holding capacity,C-organic, P and K available and CEC).The financial farming of BC ratio reached 2.25 and increased 144.56% compare to control treatment.

Modulação de atividades enzimáticas e da comunidade microbiana do solo após adição de condicionador de solo a base de cama de frango e enriquecido com Bacillus spp.

ABSTRACT The global consumption of mineral fertilizers has increased in the last 60 years. However, these fertilizers can negatively affect the soil and the atmosphere. The application of soil amendments focusing on sustainable farming practices can reduce the effects of mineral fertilization. In this study, we investigated the effects of increasing the dose of a commercial amendment using poultry litter enriched with Bacillus (SMARTGRAN) in different types of soils in Brazil under microcosm conditions. These different types of soils were classified as Nitossolo, Argissolo arênico, Argissolo alumínico, Latossolo distroférrico, and Latossolo distrófico. The biological activity in the soil was quantified by measuring the enzymes arylsulfatase, beta-glucosidase, and acid phosphatase. Additionally, bacterial diversity was evaluated by amplicon sequencing of the 16S rRNA gene and conducting phylogenetic analyses of three types of soils, which were selected because of their occurrence and fertility profiles. The results showed an increase in those enzyme activities under all conditions. The results of the analysis of the bacterial community in Nitossolo, Argissolo arênico, and Latossolo distrófico soil types showed a direct relationship between the bacterial composition in the soil and the increase in the amendment dosage. The alpha diversity indices decreased considerably because some plant-growth-promoting bacteria, such as Bacillus, Massilia, Paenibacillus, and Rhizobium, increased in relative abundance. The results indicated that an organic amendment enriched with Bacillus had a beneficial effect on different types of soil in Brazil.

Superabsorbent Polymers as a Soil Amendment for Increasing Agriculture Production with Reducing Water Losses under Water Stress Condition.

With an increasing population, world agriculture is facing many challenges, such as climate change, urbanization, the use of natural resources in a sustainable manner, runoff losses, and the accumulation of pesticides and fertilizers. The global water shortage is a crisis for agriculture, because drought is one of the natural disasters that affect the farmers as well as their country's social, economic, and environmental status. The application of soil amendments is a strategy to mitigate the adverse impact of drought stress. The development of agronomic strategies enabling the reduction in drought stress in cultivated crops is, therefore, a crucial priority. Superabsorbent polymers (SAPs) can be used as an amendment for soil health improvement, ultimately improving water holding capacity and plant available water. These are eco-friendly and non-toxic materials, which have incredible water absorption ability and water holding capacity in the soil because of their unique biochemical and structural properties. Polymers can retain water more than their weight in water and achieve approximately 95% water release. SAP improve the soil like porosity (0.26-6.91%), water holding capacity (5.68-17.90%), and reduce nitrogen leaching losses from soil by up to 45%. This review focuses on the economic assessment of the adoption of superabsorbent polymers and brings out the discrepancies associated with the influence of SAPs application in the context of different textured soil, presence of drought, and their adoption by farmers.

Changes of the Growth Rate of Wheat and Canola with Soil Amendments Application in Crop Rotation

Changes of the Growth Rate of Wheat and Canola with Soil Amendments Application in Crop Rotation

Effects of lignocellulosic biomass type on the economics of hydrothermal treatment of digested sludge for solid fuel and soil amendment applications

Digested sludge is a waste stream from anaerobic digestion (AD) in wastewater treatment plants. Hydrothermal treatment (HTT) of sludge mixed with lignocellulosic biomass is an attractive approach to improve sludge dewaterability and generate value-added products. However, process economics has not been well understood. In this study, firstly, the effect of biomass type on the energy properties of hydrochars was studied. Secondly, two scenarios were simulated to evaluate the effects of biomass type on the economics (processing 50,000 tonnes of sludge per year) of HTT of digested sludge for solid fuel and soil amendment applications. The two HTT scenarios included sludge alone and sludge-biomass mixtures (four cases for four biomass feedstocks) at 180 °C for 60 min. In both scenarios, HTT liquids were returned to existing AD facilities for biomethane production to offset the energy cost of the HTT process. The results showed that the higher heating value significantly increased from 16.0–17.0 MJ kg−1 in the sludge alone case to 18.0–23.0 MJ kg−1 in sludge–biomass mixtures (except for rice husk). With the use of saved transport cost as a revenue source, HTT of sludge–biomass led to a net present value (NPV) range of AU$ 9.9–20.3 million (20 years) and an internal rate of return (IRR) range of 25.0 %–45.2 % for solid fuel application of resulting hydrochar compared to an NPV of AU$ 18.4 million and an IRR of 55.0 % from HTT of sludge alone scenario. HTT of sludge-biomass led to a NPV range of AU$ 4.5–14.5 million and an IRR range of 17.2 %–35.7 % for soil amendment application while the hydrochar from HTT of sludge alone was not recommended for soil application due to the high contents of heavy metals. This study provides useful and critical information for process scale-up and commercialization for integration into wastewater treatment plants.

Fe3+/Mn2+ (Oxy)Hydroxide Nanoparticles Loaded onto Muscovite/Zeolite Composites (Powder, Pellets and Monoliths): Phosphate Carriers from Urban Wastewater to Soil.

The development of an efficient adsorbent is required in tertiary wastewater treatment stages to reduce the phosphate-phosphorous content within regulatory levels (1 mg L-1 total phosphorous). In this study, a natural muscovite was used for the preparation of muscovite/zeolite composites and the incorporation of Fe3+/Mn2+ (oxy)hydroxide nanoparticles for the recovery of phosphate from synthetic wastewater. The raw muscovite MC and the obtained muscovite/sodalite composite LMC were used in the powder form for the phosphate adsorption in batch mode. A muscovite/analcime composite was obtained in the pellets PLMCT3 and monolith SLMCT2 forms for the evaluation in fixed-bed mode for continuous operation. The effect of pH, equilibrium and kinetic parameters on phosphate adsorption and its further reuse in sorption-desorption cycles were determined. The characterization of the adsorbents determined the Fe3+ and Mn2+ incorporation into the muscovite/zeolite composite's structure followed the occupancy of the extra-framework octahedral and in the framework tetrahedral sites, precipitation and inner sphere complexation. The adsorbents used in this study (MC, LMC, PLMCT3 and SLMCT2) were effective for the phosphate recovery without pH adjustment requirements for real treated wastewater. Physical (e.g., electrostatic attraction) and chemical (complexation reactions) adsorption occurred between the protonated Fe3+/Mn2+ (oxy)hydroxy groups and phosphate anions. Higher ratios of adsorption capacities were obtained by powder materials (MC and LMC) than the pellets and monoliths forms (PLMCT3 and SLMCT2). The equilibrium adsorption of phosphate was reached within 30 min for powder forms (MC and LMC) and 150 min for pellets and monoliths forms (PLMCT3 and SLMCT2); because the phosphate adsorption was governed by the diffusion through the internal pores. The adsorbents used in this study can be applied for phosphate recovery from wastewater treatment plants in batch or fixed-bed mode with limited reusability. However, they have the edge of environmentally friendly final disposal being promissory materials for soil amendment applications.

Effects of application of horticultural soil amendments on decomposition, quantity, stabilisation and quality of soil carbon

Application of organic soil amendments is commonplace in horticulture to improve soil fertility. Whether this practice can also augment the soil carbon (C) pool has been of increasing interest in recent years. We used a controlled field experiment that has received annual applications of six different horticultural soil amendments for seven consecutive years. Each amendment was examined in terms of its contribution to bulk C and the distribution of C between theoretical pools, as defined by physical fractionation. Physical fractionation was combined with 13C nuclear magnetic resonance spectroscopy with cross-polarization and magic angle spinning (CPMAS NMR) analysis. Results indicated that the difference in total C concentration between treatments resulted from an increase in unprotected, free, particulate organic matter (fOM), rather than an increase in soil organic matter being occluded in aggregates or in organo-mineral complexes, and that C persisted in the fOM fraction as a result of accumulation in the alkyl C region. Unlike fresh litter or plant residues, organic amendments have undergone decomposition during the composting process (or during formation in the case of peat), in the absence of mineral soil components. This ex situ decomposition (and possible stabilization through acquired recalcitrance) could reduce the opportunity to become physically or chemically protected through association with the soil mineral phase following addition to soil. Carbon:Nitrogen (C:N) of amendment material likely influenced the rate of amendment decomposition. In addition, C:N determines the decomposition of plant litter inputs, as determined by the tea bag index.

Systems Thinking for Planning Sustainable Desert Agriculture Systems with Saline Groundwater Irrigation: A Review

Agricultural land expansion is a solution to address global food security challenges in the context of climate change. However, the sustainability of expansion in arid countries is difficult because of scarce surface water resources, groundwater salinity, and the health of salt-affected soil. Developing expansion and sustainability plans for agriculture requires systems thinking, considering the complex feedback interactions between saline groundwater, salt-affected soil, plant growth, freshwater mixing with saline groundwater, irrigation systems, and the application of soil amendments to alleviate the salinity impacts. This study presents an extensive literature review on the effects of salinity on soil and plant health, the constraints and opportunities for sustainable agriculture in Egypt, and a systems thinking approach to the feedback interactions between saline water, salt-affected soil, and the application of soil amendments to achieve required crop yields. Insights and strategies are discussed, including a system-dynamics-based decision model, irrigation systems with diversified and decentralized water sources, urban water demand management, energy availability, smart irrigation systems, and active participation of stakeholders to achieve sustainable agriculture under climate and socioeconomic changes. The insights are expected to encourage stakeholders and academic communities in the water, agriculture, and related food security sectors to develop a quantitative and systematic decision-making framework for sustainable agriculture systems in arid regions.

Effect of Mn2+/Zn2+/Fe3+ Oxy(Hydroxide) Nanoparticles Doping onto Mg-Al-LDH on the Phosphate Removal Capacity from Simulated Wastewater.

A parent Mg-Al-LDH was upgraded in its adsorption properties due to the incorporation of tri-metal species oxy(hydroxide) nanoparticles obtaining Mn2+/Zn2+/Fe3+/Mg-Al-LDH composite for the phosphate recovery from simulated urban treated wastewater. The physicochemical properties of the synthesized Mn2+/Zn2+/Fe3+/Mg-Al-LDH make promising for real application without being environmentally harmful. The performance of Mn2+/Zn2+/Fe3+/Mg-Al-LDH composite was evaluated through batch adsorption assays. The support of iron, manganese, and zinc (oxy)hydroxide nanoparticles onto the parent Mg-Al-LDH structure was performed by precipitation, isomorphic substitution, and complexation reactions. The main improvement of the Mn2+/Zn2+/Fe3+/Mg-Al-LDH composite was the highest phosphate adsorption capacity (82.3 mg∙g−1) in comparison to the parent Mg-Al-LDH (65.3 mg∙g−1), in a broad range of concentrations and the effective phosphate adsorption at neutral pH (7.5) near to the real wastewater effluents conditions in comparison to the conventional limitations of other adsorbents. The effectiveness of Mn2+/Zn2+/Fe3+/Mg-Al-LDH composite was higher than the conventional metal LDHs materials synthesized in a single co-precipitation step. The phosphate adsorption onto Mn2+/Zn2+/Fe3+/Mg-Al-LDH composite was described to be governed by both physical and chemical interactions. The support of Mn2+/Zn2+/Fe3+ oxy(hydroxide) nanoparticles over the parent Mg-Al-LDH was a determinant for the improvement of the phosphate adsorption that was governed by complexation, hydrogen bonding, precipitation, and anion exchange. The intra-particular diffusion also described well the phosphate adsorption onto the Mn2+/Zn2+/Fe3+/Mg-Al-LDH composite. Three specific stages of adsorption were determined during the phosphate immobilization with an initial fast rate, followed by the diffusion through the internal pores and the final equilibrium stage, reaching 80% of removal and the equilibrium within 1 h. The Mn2+/Zn2+/Fe3+/Mg-Al-LDH was strongly selective towards phosphate adsorption in presence of competing ions reducing the adsorption capacity at 20%. The Mn2+/Zn2+/Fe3+/Mg-Al-LDH has limited reusability, only 51% of the adsorbed phosphate could be recovered in the second cycle of the adsorption-desorption process. Around 14% of phosphate was loosely-bond to Mn2+/Zn2+/Fe3+/Mg-Al-LDH which brings the opportunity to be a new source of phosphorus. The use of eluted concentrates and the final disposal of the exhausted adsorbent for soil amendment applications can be an integral nutrient system (P, Mn, Zn, Fe) for agriculture purposes.

Effects of Soil Amendments on the Bacterial Diversity and Abundances of Pathogens and Antibiotic Resistance Genes in Rhizosphere Soil Under Drip Irrigation with Reclaimed Water

Due to reclaimed water, irrigation can cause human health and environmental risks. Soil amendments are applied to reveal the abundance of pathogens and antibiotic resistance genes in rhizosphere soil irrigated by reclaimed water and to better understand the effects of environmental factors on the rhizosphere soil bacterial composition, which has guiding significance for the reasonable use of soil amendments. In this study, the effects of biochar, bioorganic fertilizer, humic acid, loosening soil essence, and corn vinasse on bacterial community diversity and certain gene abundances in rhizosphere soil under drip irrigation with reclaimed water were studied using high-throughput assays and quantitative PCR. The results showed that biochar significantly increased pH, organic matter, and total nitrogen contents in the rhizosphere soil. The corn vinasse significantly decreased soil pH and increased the contents of total nitrogen and total phosphorus but significantly increased the soil EC value (P<0.05). The effects of the five soil amendments on the α-diversity of rhizosphere bacteria were not significantly different. The bacterial community structure and diversity of rhizosphere bacteria were similar at different taxonomic levels, but their relative abundance was different. α-Proteobacteria, γ-Proteobacteria, Bacteroidia, Actinobacteria, Acidimicrobiia, and Anaerolineae were the dominant bacteria in all treatments. The dominant genera consisted of Pseudomonas, Sphingobium, Sphingomonas, Cellvibrio, Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium, Flavobacterium, and Algoriphagus (relative abundance>1%). Correlation analysis of environmental factors showed that the composition of the rhizosphere bacterial community was strongly correlated with pH, EC, total nitrogen, and total phosphorus content. The abundances of pathogenic bacteria and antibiotic resistance genes were 103-107 copies·g-1 and 104-108 copies·g-1, respectively. There were significant differences in the detection levels of pathogens and antibiotic resistance genes. Bioorganic fertilizer, loosening soil essence, and corn vinasse significantly increased the abundances of some antibiotic resistance genes, whereas humic acid and corn vinasse significantly decreased the abundances of Pseudomonas syringae, Ralstonia solanacearum, and total coliforms (P<0.05). A significant correlation was found between pathogens (Arcobacter, Bacillus cereus, Pantoea agglomerans, and Fecal bacteroidetes) and antibiotic resistance genes (tetA, tetB, tetO, tetQ, sul1, ermB, and ermC). In conclusion, while monitoring pathogens and antibiotic resistance genes in the agricultural environment under reclaimed water irrigation, attention should be paid to the rational application of soil amendments to avoid exacerbating the spread of biological contamination.

The Role of Digital Soil Information in Assisting Precision Soil Management

Soil information is the basis for the site-specific management of soils. The study aimed to digitize soil information and classify it into soil mapping units (SMUs) using geostatistics. The study area was grouped into 12 SMUs, or management zones. The pH of the soils ranged from 7.3 in SMU2 to 8.6 in SMU5. Most SMUs exhibited low total nitrogen (TN) that could be attributed to very low soil organic carbon (SOC) in the soils. Available phosphorus (AvP) was very low in all the mapping units. The exchangeable K varied between 0.12 cmol(+) kg−1 (SMU7) and 0.95 cmol(+) kg−1 (SMU10). SMU12 was identified as marginally sodic and at a high risk of developing severe alkalinity unless possible management measures are implemented. Our findings show that a lack of soil information causes an imbalance between soil requirements and external nutrient inputs, negatively affecting crop production. Therefore, high-resolution digital soil information can assist the site-specific application of soil nutrients and amendments based on spatial variability in line with soil requirements.

Application of soil amendments to enhance soil carbon and biological properties in a paddy field under elevated CO2 conditions

ABSTRACT A field experiment was carried out to elucidate the effect of elevated carbon dioxide (eCO2 – 550 ± 30 ppm) on soil enzymes (dehydrogenase, β-glucosidase, fluorescein diacetate, urease, acid and alkaline phosphatase), soil carbon pool (Soil Organic Carbon (SOC), Microbial Biomass Carbon (MBC), oxidizable carbon, humic acid (HA), fulvic acid (FA) fractions), microbial population dynamics (heterotrophs, fungi, actinobacteria, diazotrophs, methanotrophs, and total anaerobes), carbon sequestration and yield in a flooded paddy soil in open top chambers (OTCs) in relation to rhizospheric and bulk soil. Responses of most of the observed parameters to eCO2 with biochar application in rhizosphere soil were significantly higher. The carbon (C) sequestration potential was found higher in the biochar applied plot under eCO2 with 0.59 Mg C sequestered ha−1. The same recorded the highest biomass yield and grain yield which is 12.8 and 30.8% higher than the control. Principal Component Analysis (PCA) recognized soil dehydrogenase, β – glucosidase, SOC, FA, Substrate Induced Respiration (SIR), metabolic quotient (qCO2) and counts of heterotrophs as key drivers of variability. The current study thus provides some dependable biological indicators to assess the paddy ecosystems, vis-à-vis anticipatory climate change.