Amendment Ratio Research Articles

Commercial compost amendments inhibit the bioavailability and plant uptake of per- and polyfluoroalkyl substances in soil-porewater-lettuce systems

Compost is widely used in agriculture as fertilizer while providing a practical option for solid municipal waste disposal. However, compost may also contain per- and polyfluoroalkyl substances (PFAS), potentially impacting soils and leading to PFAS entry into food chains and ultimately human exposure risks via dietary intake. This study examined how compost affects the bioavailability and uptake of eight PFAS (two ethers, three fluorotelomer sulfonates, and three perfluorosulfonates) by lettuce (Lactuca sativa) grown in commercial organic compost-amended, PFAS spiked soils. After 50 days of greenhouse experiment, PFAS uptake by lettuce decreased (by up to 90.5 %) with the increasing compost amendment ratios (0–20 %, w/w), consistent with their decreased porewater concentrations (by 30.7–86.3 %) in compost-amended soils. Decreased bioavailability of PFAS was evidenced by the increased in-situ soil-porewater distribution coefficients (Kd) (by factors of 1.5–7.0) with increasing compost additions. Significant negative (or positive) correlations (R2 ≥ 0.55) were observed between plant bioaccumulation (or Kd) and soil organic carbon content, suggesting that compost amendment inhibited plant uptake of PFAS mainly by increasing soil organic carbon and enhancing PFAS sorption. However, short-chain PFAS alternatives (e.g., perfluoro-2-methoxyacetic acid (PFMOAA)) were effectively translocated to shoots with translocation factors > 2.9, increasing their risks of contamination in leafy vegetables. Our findings underscore the necessity for comprehensive risk assessment of compost-borne PFAS when using commercial compost products in agricultural lands.

Salty bio-converted organic fertilizer modulates soil greenhouse gas emissions

The black soldier fly frass (BSFF) can be applied as a bio-converted organic fertilizer in agriculture and has been shown to affect soil properties and plant growth. However, the impacts of salty BSFF derived from kitchen waste (KW) on soil properties and greenhouse gas emissions are unclear. The impacts of salty black soldier fly (Hermetia illucens) frass derived from KW on soil properties and greenhouse gas emissions were investigated. The frass amendments increased soil dissolved organic carbon and nitrogen (0.5–1.6 and 0.1–15 fold) and soil ammonium (0.5–31 fold) content, with a similar trend as soil pH (0∼0.4 fold) and electrical conductivity (2–131 fold). Soil gas emissions (CO2 and N2O) increased by frass amendments. The frass amendment affected the microbial communities followed by the addition rates, with the enriched beneficial bacteria (Nocardioides) and depleted denitrification fungi (Penicillium) as well as the C- and N-cycle related microbial functional genes. The nirS and amoB genes were the critical factors in the soil N2O emission with the frass amendment ratio in the soil. The lig and glx genes involved in lignin decomposition contributing to the increase of soil CO2 emission. These findings indicated that there is a need to inform research and policy decisions aimed at developing and promoting appropriate standards and guidelines for quality production, sustainable utilization, and successful integration of the frass into existing organic fertilizer framework and soil systems.

MnFe2O4-biochar decreases bioavailable fractions of thallium in highly acidic soils from pyrite mining area

The prevalence of toxic element thallium (Tl) in soils is of increasing concern as a hidden hazard in agricultural systems and food chains. In the present work, pure biochar (as a comparison) and jacobsite (MnFe2O4)-biochar composite (MFBC) were evaluated for their immobilization effects in Tl-polluted agricultural soils (Tl: ∼10 mg/kg). Overall, MFBC exhibited an efficient effect on Tl immobilization, and the effect was strengthened with the increase of amendment ratio. After being amended by MFBC for 15 and 30 days, the labile fraction of Tl in soil decreased from 1.55 to 0.97 mg/kg, and from 1.51 to 0.88 mg/kg, respectively. In addition, pH (3.05) of the highly acidic soil increased to a maximum of 3.97 after the immobilization process. Since the weak acid extractable and oxidizable Tl were the preponderantly mitigated fractions and displayed a negative correlation with pH, it can be inferred that pH may serve as one of the most critical factors in regulating the Tl immobilization process in MFBC-amended acidic soils. This study indicated a great potential of jacobsite-biochar amendment in stabilization and immobilization of Tl in highly acidic and Tl-polluted agricultural soils; and it would bring considerable environmental benefit to these Tl-contaminated sites whose occurrence has significantly increased in recent decades near the pyrite or other sulfide ore mining and smelting area elsewhere.

Role of different natural materials in reducing nitrogen loss during industrial sludge composting: Modelling and optimization

In this study, the effects of pumice, expanded perlite, and expanded vermiculite on nitrogen loss were examined for industrial sludge composting using the Box-Behnken experimental design. The independent factors and their levels were selected as amendment type, amendment ratio, and aeration rate, and codded as x1, x2, and x3 at 3 levels (low, center, and high). The statistical significance of independent variables and their interactions were determined at 95% confidence limits by Analysis of Variance. The quadratic polynomial regression equation produced to predict the responses was solved and the optimum values of the variables were predicted by analyzing the three-dimensional response surfaces plots. The optimum conditions for minimum nitrogen loss by the regression model were as pumice of amendment type, 40% of amendment ratio, and 6 L/min of aeration rate. In this study, it was observed that time-consuming and laborious laboratory work can be minimized with the Box-Behnken experimental design.

Nitrogen removal mechanisms in biochar-amended sand filters treating onsite wastewater.

The performance of biochar-amended sand filters treating septic tank effluent (STE) was investigated in bench-scale columns. Softwood biochar showed higher NH4 + -N adsorption capacity (1.3mgNg-1 ), and its water holding capacity (0.57gml-1 ) was significantly higher than sand (0.26gml-1 ). Two biochar amendment ratios (10% and 30%) were selected for STE treatment in short-term (20 days) and long-term (8 months) studies. During the short-term experiment, the overall total nitrogen removal efficiency was greater in biochar-amended sand columns (94.7%-95.6%) than in 100% sand columns (71.2%) due to the additional NH4 + -N adsorption by biochar. Greater nitrification performance was also observed in biochar-amended columns (87.1%-96.3%) than in 100% sand columns (61.4%) during long-term operation when alkalinity was insufficient. The nitrification performance in biochar-amended columns resumed more quickly (<7 days) after sufficient alkalinity was amended. The density of total biomass and nitrifying bacteria in biochar-amended columns (30%) were significantly higher at all experimental stages, suggesting biochar served as a growth media for enhanced biomass growth. The alkalinity changes and STE composition fluctuation had little impact on the nitrification performance of the 30% biochar-amended sand columns. In addition, biochar surface functional groups and zeta potential changed little after long-term STE filtration. Collectively, the results demonstrated proper biochar amendment ratio (30%) could enhance the nitrification performance of sand filters treating STE by increasing the system hydraulic retention time, providing additional alkalinity for nitrification, and serving as a growth media for enhanced biomass growth.

Effects of biochar and vermicompost on microorganisms and enzymatic activities in greenhouse soil

The effects of different contents of biochar and vermicompost on the microbial and enzymatic activities of greenhouse soil were determined to provide a theoretical basis for improving the quality of greenhouse soil. The experiment was conducted in a greenhouse using potted tomatoes. Five treatments consisted of different amount ratios of organic amendments: 1% biochar (BC1), 3% biochar (BC3), 5% biochar (BC5), 3% vermicompost (VC3), and 5% vermicompost (VC5), with no addition of organic amendments as the control (CK). Compared with CK, the pH, organic matter content, and DOC concentration increased in treatment groups. The organic matter content of BC3 and BC5 significantly increased by 54.6% and 72.8%, respectively, and DOC concentration of BC3 significantly increased by 43.9%. Biochar and vermicompost significantly increased the diversity of bacterial and fungal communities in soil, as well as the abundance of Actinomycetes, Acidobacteria, Ascomycetes, and Aspergillus, and reduced the abundance of Aspergillus. The activities of urease and alkaline phosphatase were significantly increased, and the activity of nitrate reductase was inhibited in all treatment groups compared with CK. In addition, a highly significant positive correlation was observed among pH, Acidobacteria phylum abundance, and alkaline phosphatase activity in all treatments. DOC concentration was positively correlated with pH, organic matter content, Acidobacteria phylum abundance and alkaline phosphatase activity. Biochar and vermicompost were effective in improving the physicochemical properties of greenhouse soil, enhancing microbial diversity, and affecting enzymatic activities. Therefore, BC3 (3% biochar) had the most significant effect on community diversity and alkaline phosphatase and nitrate reductase activities. VC5 (5% vermicompost) had the best promotion effect on urease activity. This study highlights that biochar and vermicompost as organic amendments are recommended to improve the quality of greenhouse soils.

Rhizosphere activity induced mobilization of heavy metals immobilized by combined amendments in a typical lead/zinc smelter-contaminated soil

The persistence of the stabilization effect of amendments on heavy metals (HMs) is of great concern when they are used for remediating HM-contaminated soil. Here, pot experiments were conducted to investigate the effects of two consecutive seasons of vegetable cultivation on the mobilization of HMs (Cu, Pb, Zn, and Cd) immobilized by different application ratios (0, 20, 40, and 80 g kg−1, labelled C0, C2, C4, and C8) of a combined amendments (lime: sepiolite: biochar: humic acid = 2:2:1:1). The results showed that HM bioavailability decreased with increasing application ratios of the combined amendments in control (CK) treatments. The DOC contents, HM bioavailability, and HM contents in the leaves of vegetables increased, but the pH decreased during two consecutive seasons of vegetable cultivation; however, the HM bioavailability in the C2, C4, and C8 treatments was lower than that in the C0 treatments with vegetables. Catalase, urease, alkaline phosphatase, and dehydrogenase activities in the combined amendment treatments with and without vegetables were decreased compared to those in the C0 treatments. The relative abundances of the dominant bacterial phyla in the different treatments were Actinobacteria > Proteobacteria > Chloroflexi > Acidobacteria > Gemmatimonadetes > Bacteroidetes for the first season and Proteobacteria > Actinobacteria > Chloroflexi > Acidobacteria > Bacteroidetes > Gemmatimonadetes for the second season. Correlations showed that the pH and DOM properties during two consecutive seasons of vegetable cultivation were important factors influencing HM bioavailability, enzyme activity, and bacterial community composition. The bacterial community composition shift indirectly influenced the mobilization of HMs immobilized by the combined amendments. Thus, rhizosphere activity induced the mobilization of HMs immobilized by combined amendments during two consecutive seasons of vegetable cultivation.

Road MAP of National Development Through The V Amendment of The 1945 Constitution

The actualization of the 1945 Constitution of the Republic of Indonesia in the administration of the state, after 23 years of reform or after 4 amendments have been made, it is deemed necessary/important to carry out the 5th amendment. solely on the needs/allegances of the state and it is relevant to the affairs of the life of all Indonesian people. The research method used is normative juridical research considering that what is studied is the result of books and regulations regarding: the ratio of amendments to the 1945 Constitution of the Republic of Indonesia, public participation in constitutional changes, the national development planning system (SPPN), and reconstruction of the state policy model of the main principles of the state. . The basic question related to the current state administration issue is bringing back the State Policy Guidelines to be an important choice? In the course of Indonesia's state administration, it seems that a national development roadmap is urgently needed, in order to realize a good government, and maintain the sustainability of national development (sustainable government) so that the government (President) of the development program becomes a Vision-Mission that must be continued even though the President changes.

Influence of Organic Amendments on Soil Carbon Sequestration Potential of Paddy Soils under Two Irrigation Regimes

Soil organic carbon (OC) is one of the most important soil components regulating soil quality, fertility and agronomic productivity as well as the global carbon (C) cycle. Soil acts as a sink for global C, which can be influenced by the water regime and organic matter (OM) management in field. The aim of this study is to evaluate the effect of the application of different organic amendments on C sequestration in paddy soils under contrasting irrigation regimes. A 4-month pot experiment was conducted under net house conditions and the treatments were composed of two organic amendments: rice straw (RS) and poultry manure (PM); four application rates of amendment: 0 g (control), 2.5 g, 5.0 g and 15.0 g kg−1 soil; and two irrigation regimes: (i) continuous waterlogging condition (CWL) and (ii) alternate wetting and drying (AWD). After the incubation period, soil samples were collected from the pot and isolated into labile (&gt;53 µm) and mineral-associated (&lt;53 µm) OM. Bulk (before and after incubation) and fractionated soil samples were analyzed for OC, total nitrogen (N), C:N ratio; and C sequestration percentage was calculated. Relatively higher amounts of soil OC were present in CWL condition (1.23%) than AWD (1.13%). The C sequestration potential also showed the similar trend (CWL: 47% &gt; AWD: 35%). This was explained by the induced aerobic condition in between the anerobic condition in AWD and the continuous anaerobic condition in CWL which resulted in a difference in OM decomposition. The mineral-associated OM fraction (&lt;53 µm) was higher in the CWL condition than AWD condition which also indicated the importance of the chemical stabilization of OC (OC bound to minerals) in the CWL condition. The application of PM led to a significant increase (45%) in C sequestration potential than RS (37%). This could be attributed to C:N ratio and probable biochemical composition of amendments which resulted in lower decomposability of PM than RS, and also in line with the higher distribution of OC in mineral-bound OM than labile fraction. The application of higher organic amendments did not increase OC content, and declined C sequestration potential in soils as the microbial activity presumably did not match with the amendment amount. Overall, C sequestration potential was higher with 5 g PM kg−1 soil application under CWL-irrigated paddy soil. The findings indicated the need to pay more attention to the selection of the proper type and rate of organic amendments for higher C sequestration in soil under a specific irrigation system for sustainable agriculture.

Carbon to nitrogen ratio and quantity of organic amendment interactively affect crop growth and soil mineral N retention

Using organic amendments to improve arable soils in the long term is a careful balancing act of applying amendments with the right carbon to nitrogen ratio (C:N ratio) at adequate quantity to avoid nitrogen (N) leaching while promoting or retaining crop growth in the short term. So far, most studies examining the relationship between C:N ratio and N mineralization and immobilization were done without plants. In this study we explored how crop biomass and N leaching change with increasing C:N ratio and quantity of organic amendments to arable soil. We conducted an open-air mesocosm experiment with organic amendments application across a range in C:N ratio (10 to 60) and quantity (10 to 50 ton ha-1) to sandy arable soil using a full-factorial design. Spring wheat was planted and grown for six months during which three rainfall events were simulated to test treatment effects on N leaching. Applying amendments with a C:N ratio of 20 and higher decreased crop biomass and increased mineral soil N, while amendments with a C:N ratio of 10 had the opposite effect. Applying larger quantities of amendments reinforced the effect of the C:N ratio on crop biomass. N leaching remained unaffected by either amendment C:N ratio or quantity or even mineral fertilizer as N leaching only occurred in the control treatment without plants. Our results suggests that growing a crop is adequate to prevent N leaching. Applying organic amendments do not pose a different risk regarding N leaching when compared to mineral fertilizer and slurry.

Using some Natural Minerals to Remove Cadmium from Polluted Water

Water scarcity is one of the most important problems facing humanity in various fields such as economics, industry, agriculture, and tourism. This may push people to use low-quality water like industrial-wastewater. The application of some chemical compounds to get rid of heavy metals such as cadmium is an environmentally harmful approach. It is well-known that heavy metals as cadmium may induce harmful problems when present in water and invade to soil, plants and food chain of a human being. In this case, man will be forced to use the low quality water in irrigation. Application of natural materials instead of chemicals to remove cadmium from polluted water is an environmental friendly approach. Attention was drawn in this research work to use some natural minerals as zeolite, bentonite and montmorillonite to adsorb cadmium element from polluted water. Various concentrations of cadmium in solutions 10, 30 and 50 ppm were treated with three different ratios of each mineral; 1, 3 and 5% (W/V). The obtained results proved that increasing the ratio of amendments to 5% increased Cd adsorption from solution particularly at 50ppm Cd. Zeolite obtained the highest ratio of adsorption (47.90 ppm), followed by montmorillonite (44.99 ppm) and the lowest was bentonite (38.97 ppm). Therefore, it can be recommended that addition of zeolite is the most favorable material to remove Cd element from polluted water.

Identifying the maturity of co-compost of olive mill waste and natural mineral materials: Modelling via ANN and multi-objective optimization

In this study, olive mill waste (OMW) and natural mineral amendments were co-composted to evaluate the compost maturity efficiency. The results were modelled by Feed-Forward Neural Networks (FF-NN) and Elman-Recurrent Neural Networks (ER-NN) and compared Response Surface Methodology (RSM). According to RSM produced a prediction error of more than 10% while Neural Networks (NNs) models were <2%. From, multi-objective optimization, the most suitable materials were expanded vermiculite and pumice with overall desirabilities of 0.60 and 0.56, respectively. The optimum amendment ratios were achieved with 14.3% of expanded vermiculite and 16.0% of pumice for OMW composting. Multivariate Analysis of Variance (MANOVA) results indicated that the materials had a strong effect on composting in parallel with the optimization results. NNs were predictors with superior properties to model the composting processes, can be used as modeling tools in many areas that are difficult and costly to perform new experiments.

Efficiency of biochar, nitrogen addition, and microbial agent amendments in remediation of soil properties and microbial community in Qilian Mountains mine soils.

Lacking systematic evaluations in soil quality and microbial community recovery after different amendments addition limits optimization of amendments combination in coal mine soils. We performed a short‐term incubation experiment with a varying temperature over 12 weeks to assess the effects of three amendments (biochar: C; nitrogen fertilizer at three levels: N‐N1~N3; microbial agent at two levels: M‐M1~M2) based on C/N ratio (regulated by biochar and N level: 35:1, 25:1, 12.5:1) on mine soil properties and microbial community in the Qilian Mountains, China. Over the incubation period, soil pH and MBC/MBN were significantly lower than unamended treatment in N addition and C + M + N treatments, respectively. Soil organic carbon (SOC), total nitrogen (TN), available nitrogen (AN), available phosphorus (AP), available potassium (AK), microbial biomass carbon (MBC), and nitrogen (MBN) contents increased significantly in all amended treatments (p < .001). Higher AP, AK, MBC, MBN, and lower MBC/MBN were observed in N2‐treated soil (corresponding to C/N ratio of 25:1). Meanwhile, N2‐treated soil significantly increased species richness and diversity of soil bacterial community (p < .05). Principal coordinate analysis further showed that soil bacterial community compositions were significantly separated by N level. C‐M‐N treatments significantly increased the relative abundance (>1%) of the bacterial phyla Bacteroidetes and Firmicutes, and decreased the relative abundance of fungal phyla Chytridiomycota (p < .05). Redundancy analysis illustrated the importance of soil nutrients in explaining variability in bacterial community composition (74.73%) than fungal composition (35.0%). Our results indicated that N addition based on biochar and M can improve soil quality by neutralizing soil pH and increasing soil nutrient contents in short‐term, and the appropriate C/N ratio (25:1) can better promote microbial mass, richness, and diversity of soil bacterial community. Our study provided a new insight for achieving restoration of damaged habitats by changing microbial structure, diversity, and mass by regulating C/N ratio of amendments.

Use of botanicals in root-knot nematode control: a meta-analysis

This meta-analysis was conducted to quantitatively analyze the efficacy of plant residues and plant derivatives of various plant species against root-knot nematodes (Meloidogyne spp.). Publications investigating root-knot nematodes control with plant-based amendments, i.e., plant residues (i.e., crop trash/stubble, pomace, oil cakes) and plant derivatives, such as extracts and powders of leaf, flower and fruit, were identified in Scopus® and ScienceDirect® databases and other literature. A meta-analysis was done by calculating the natural logarithm of response ratios of different plant-based soil amendments against root-knot nematodes. Plant residues reduced the number of root-knot nematode and its damage nearly by 49% compared to the control in general. Plant residues of Raphanus sativus (radish) and Oryza sativa (rice) demonstrated the highest root-knot nematode control, with up to 85% reduction in damage and root-knot nematode population densities when compared to the control. Leaf extracts of Allium tuberosum (garlic) and leaf powder of Laurelia sempervirens (Peruvian nutmeg) demonstrated the highest percentage reduction of root-knot nematode population densities and damage.

Effects of pyrolysis temperature, feedstock type and compaction on water retention of biochar amended soil

Recent studies on water retention behaviour of biochar amended soil rarely considers the effect of pyrolysis temperature and also feedstock type into account. It is well known that pyrolysis temperature and feedstock type influences the physical and chemical properties of biochar due to stagewise decomposition of structure and chemical bonds. Further, soil density, which is in a loose state (in agricultural applications) and dense (in geo-environmental engineering applications) can also influence water retention behaviour of biochar amended soils. The major objective of this study is to investigate the water retention properties of soil amended with three different biochars in both loose and dense state. The biochars, i.e. water hyacinth biochar (WHB), chicken manure biochar (CMB) and wood biochar (WB) were produced in-house at different pyrolysis temperature. After then, biochars at 5% and 10% (w/w%) were amended to the soil. Water retention behaviour (soil suction and gravimetric water content) was studied under drying and wetting cycle simulated by varying relative humidity (RH, 50–90%). Results show that 10% WHB produced at 300 °C were found to possess highest water retention. CMB is found to possess higher water retention than WB for 10% amendment ratio. In general, the addition of three biochars (at both 300 °C and 600 °C) at 10% (w/w) significantly improved the water retention at all suction ranges in both loose and dense compaction state as compared to that of the bare soil. The adsorption (wetting) and desorption (drying) capacity of biochar amended soils is constant at corresponding RH.

The Impact of Lignite and Wheat Straw Biochar Application on Structural Traits of Pot-Grown Nitraria Schoberi L. and Soil Properties

Applying proper soil amendments in arid and semi-arid areas improves soil quality and promotes plant growth. Lignite and Wheat Straw Biochar (WSB) are soil amendments that can be used to improve soil quality and plant productivity. Nitraria Schoberi L. is a halophyte shrub from Nitrariaceae family that is planted in degraded rangelands for forage production and soil conservation. In this research, we investigated the effects of lignite and WSB on structural traits (e.g., height, crown diameter, area and volume, leaf area, perimeter, etc.) of N. Schoberi and soil properties. The lignite and WSB amendments were applied at rates of 0, 1.25, 2.5, and 3.75% (weight/weight) in six replications. The experiment was conducted in pots inside a greenhouse. Statistical analysis was performed by one-way and two-way analyses of variance using the SPSS21 statistical software. Our results revealed that lignite and WSB amendments significantly improved soil properties and increased structural traits of the N. Schoberi. Trait enhancement was considerably increased by incorporating a larger ratio of amendments to soil during the experiment. In particular, we found that an application of 3.75% (w/w) of both amendments among the ones tested provided the best rate to reach the largest improvement in soil properties and the largest growth of N. Schoberi. The results demonstrated that lignite and WSB can be used to enhance soil chemical and biological properties to promote the productivity of N. Schoberi. Our results suggest that the application of lignite and WSB effectively improved poor soil properties in the studied clay loam solonchak rangeland soil. We recommend incorporating these amendments in the restoration of rangelands with alkaline soils using N. Schoberi.

Effects of amendments on the bioavailability, transformation and accumulation of heavy metals by pakchoi cabbage in a multi-element contaminated soil.

This study aims to assess the effect of green waste compost (GWC), biochar (BC) and humic acid (HA) amendments of an alkaline heavy metal-contaminated soil. In this study, amendments with GWC, GWC + BC and GWC + HA were applied to the heavy metal-contaminated soil in four application rates (0, 1, 2 and 5%), and was aimed at substantially mitigating the bioavailability of heavy metals for pakchoi cabbage from the sewage irrigation soils. The addition of different ratios of amendments can increase the pH of the soil by 0.11–0.30 units and also increase the organic matter content by 3.1–35.1%. The concentration of available arsenic (As), cadmium (Cd), zinc (Zn) and copper (Cu) in the CaCl2 extract was decreased effectively by all the amendments, except for the increase in the available concentration of As by compost–humic acid (T8) in the soil. Compared with the control, the CaCl2 extractable Cd was decreased by 33–48% after the addition of different ratios of amendments in the soil. Moreover, by increasing the content of compost and compost–biochar in combinations, easily exchangeable fractions of As, Cd, Zn and Cu were decreased, while the oxidation fraction and residual fractions were increased. When the soil amendments were applied, fresh weight of the root and shoot increased by 29–63% and 39–85%, respectively. Cd concentration in the roots and shoots of the pakchoi cabbage decreased by 21–44% and 26–53%, respectively, after adding different ratios of amendments. All the amendments were effective in reducing the Cd, Zn and Cu uptake by the roots and shoots of the pakchoi cabbage, and simultaneously reduce the absorption of As in the roots of pakchoi cabbage. As soil amendments, GWC alone or GWC + BC/GWC + HA application can significantly reduce the heavy metal levels in pakchoi cabbage while increasing the biomass production and higher application rate is more effective than the lower application rate.

C and N dynamics with repeated organic amendments can be simulated with the STICS model

Repeated applications of organic amendments increase soil organic carbon (SOC) storage and nitrogen (N) availability for crops. Soil-crop models can facilitate the study of these effects and optimize the management of amendments. In soil-crop models, C and N mineralization of amendments is simulated by several pools of soil organic matter which have their specific turnover rate. We used the STICS model to quantify the effects of amendments on C and N dynamics in the long-term QualiAgro experiment, in which four amendments were spread every 2 years since 1998. We studied the model’s ability to simulate laboratory incubation and field experiments, depending on the calibration method and the partitioning of the amendment into one or two pools. The one-pool model simulated C and N dynamics in the field experiment as accurately as the two-pools model with a calibration based on field data. However, C and N dynamics measured under laboratory conditions could only be simulated with the two-pools model, which was then used to simulate C and N in the field. The root mean square errors were 1.6 t DM ha−1 for grain yield, 2.6 t C ha−1 for SOC and 41 kg N ha−1 for soil mineral N. Model parameters could be determined using the C:N ratio of amendments and the indicator of remaining organic carbon (IROC), measured at the laboratory. The STICS model can thus be used to simulate SOC and N dynamics with long-term amendments with a simple calibration.

Phytostabilization of store‐and‐release cover made with phosphate mine wastes in arid and semiarid climate using wild local plants

AbstractTo limit the generation of acid mine drainage at the Kettara abandoned mine (KAM) located 35 km North‐North West of Marrakech, Morocco, a store‐and‐release (SR) system was constructed. The SR system made of two materials, the cover constituted by phosphate waste (PW) rock and lower layer was the coarse‐grained tailings of KAM. The lower layer restricted water in the interface and the stocked water during wet periods by the PW layer is released during dry ones. The objective of this study is to assess the phytostabilization ability of SR cover using local plants. Seeds of five wild local plants: Atriplex semibaccata R. Br., Peganum harmala L., Asparagus horridus L., Launaea arborescens (Batt.) Murb., and Vicia sativa L., were selected and planted. Pots experiment of phosphate mine wastes (PW) and PW amended with different ratios of compost and commercial peat. These pot experiments were performed in greenhouse conditions. The germination and growth parameters studied were germination percentage (GP), mean germination time (MGT), speed of germination (SG), epigeal height, and hypogeal length evolution. Cd, Ni, As, Cu, and Zn concentrations in substrates and in plant fractions were analyzed. The results obtained using 100% PW (PW100) as the highest GP (87.50%) were obtained for A. semibaccata R. Br., followed by V. sativa L. with GP (25.00%). The uppermost MGT results showed that A. semibaccata R. Br. (MGT = 4.39) and L. arborescens (Batt.) Murb. (MGT = 1.91), were the most suitable for the phosphate mine wastes. Concerning SG, the values obtained were 19.07 and 5.11, for A. semibaccata R. Br., and L. arborescens (Batt.) Murb., respectively. Regarding the epigeal and hypogeal length, respectively, the best values were obtained for A. semibaccata R. Br., and V. sativa L., with 40.70 cm and 13.73 cm for epigeal length and 20.97 cm and 82.67 cm for hypogeal length. The results obtained with different ratios of amendments showed that the application of 10% compost and 20% organic fertilizer, showed significantly higher germination index, hypogeal, and epigeal growth for A. semibaccata R. Br., V. sativa L., and L. arborescens (Batt.) Murb. The concentrations of the studied trace elements in selected plant fractions does not exceed domestic animal metal toxicity limits in any trial. The concentrations of these trace elements in plant hypogeal fractions were significantly (p &lt; .05) higher than those of epigeal fractions. The transfer and bio‐concentration factors were &lt;1 in all selected plants. According to these results, we can affirm that A. semibaccata R. Br., as a key species and that V. sativa L. and L. arborescens (Batt.) Murb. are also good candidates for the phytostabilization necessary for the SR cover.

Degradation of Carbendazim in Soil: Effect of Sewage Sludge-Derived Biochars.

Application of biochar in soils can affect the soil properties and, in turn, the fate of pesticides. Batch experiments were conducted to investigate the effect of sewage sludge-derived biochars on the dissipation of a fungicide carbendazim in soil, and the transformation of carbendazim in soil was also studied. Results showed that the dissipation of carbendazim was fastest in a loamy soil SD with a half-life of 11.0 d among the three kinds of soils tested in this study. A dual effect (both acceleration and inhibition) of sewage sludge-derived biochars on carbendazim degradation in soil was reported. The addition of 10% biochars produced at 700 °C (BC 700) in soil could accelerate the carbendazim degradation, but an inhibitory effect was observed for 10% BC 300 or BC 500. Degradation of carbendazim was significantly inhibited when 0.5 or 5% BC 700 was added in soil but accelerated when the amendment ratio of BC 700 was increased to 10%. Such complex effects of the sewage sludge biochar should be taken into consideration in risk assessment of pesticides and the biochar effects on soil remediation. Eight metabolites of carbendazim were characterized, seven of which were reported in unamended soil for the first time. The metabolic pathways of carbendazim in soil are proposed.