Influences of rice straw biochar and organic manure on forage soybean nutrient and Cd uptake

Ca(H2PO4)2 and MgSO4 activated nitrogen-related bacteria and genes in thermophilic stage of compost

This study was conducted to investigate the effects of Ca(H2PO4)2 and MgSO4 on the bacterial community and nitrogen metabolism genes in the aerobic composting of pig manure. The experimental treatments were set up as control (C), 1% Ca(H2PO4)2 + 2% MgSO4 (CaPM1), and 1.5% Ca(H2PO4)2 + 3% MgSO4 (CaPM2), which were used at the end of composting for potting trials. The results showed that Ca(H2PO4)2 and MgSO4 played an excellent role in retaining nitrogen and increasing the alkali-hydrolyzed nitrogen (AN), available phosphorus (AP), and available potassium (AK) contents of the composts. Adding Ca(H2PO4)2 and MgSO4 changed the microbial community structure of the compost. The microorganisms associated with nitrogen retention were activated. The complexity of the microbial network was enhanced. Genetic prediction analysis showed that the addition of Ca(H2PO4)2 and MgSO4 reduced the accumulation of nitroso-nitrogen and the process of denitrification. At the same time, despite the reduction of genes related to nitrogen fixation, the conversion of ammonia to nitrogenous organic compounds was promoted and the stability of nitrogen was increased. Mantel test analysis showed that Ca(H2PO4)2 and MgSO4 can affect nitrogen transformation-related bacteria and thus indirectly affect nitrogen metabolism genes by influencing the temperature, pH, and organic matter (OM) of the compost and also directly affected nitrogen metabolism genes through PO43- and Mg2+. The pot experiment showed that composting with 1.5% Ca(H2PO4)2 + 3% MgSO4 produced the compost product that improved the growth yield and nutrient content of cilantro and increased the fertility of the soil. In conclusion, Ca(H2PO4)2 and MgSO4 reduces the loss of nitrogen from compost, activates nitrogen-related bacteria and genes in the thermophilic phase of composting, and improves the fertilizer efficiency of compost products. KEY POINTS: • Ca(H2PO4)2 and MgSO4 reduced the nitrogen loss and improved the compost effect • Activated nitrogen-related bacteria and altered nitrogen metabolism genes • Improved the yield and quality of cilantro and fertility of soil.

Recent advances in biochar amendments for immobilization of heavy metals in an agricultural ecosystem: A systematic review

Over the last several decades, extensive and inefficient use of contemporary technologies has resulted in substantial environmental pollution, predominantly caused by potentially hazardous elements (PTEs), like heavy metals that severely harm living species. To combat the presence of heavy metals (HMs) in the agrarian system, biochar becomes an attractive approach for stabilizing and limiting availability of HMs in soils due to its high surface area, porosity, pH, aromatic structure as well as several functional groups, which mostly rely on the feedstock and pyrolysis temperature. Additionally, agricultural waste-derived biochar is an effective management option to ensure carbon neutrality and circular economy while also addressing social and environmental concerns. Given these diverse parameters, the present systematic evaluation seeks to (i) ascertain the effectiveness of heavy metal immobilization by agro waste-derived biochar; (ii) examine the presence of biochar on soil physico-chemical, and thermal properties, along with microbial diversity; (iii) explore the underlying mechanisms responsible for the reduction in heavy metal concentration; and (iv) possibility of biochar implications to advance circular economy approach. The collection of more than 200 papers catalogues the immobilization efficiency of biochar in agricultural soil and its impacts on soil from multi-angle perspectives. The data gathered suggests that pristine biochar effectively reduced cationic heavy metals (Pb, Cd, Cu, Ni) and Cr mobilization and uptake by plants, whereas modified biochar effectively reduced As in soil and plant systems. However, the exact mechanism underlying is a complex biochar-soil interaction. In addition to successfully immobilizing heavy metals in the soil, the application of biochar improved soil fertility and increased agricultural productivity. However, the lack of knowledge on unfavorable impacts on the agricultural systems, along with discrepancies between the use of biochar and experimental conditions, impeded a thorough understanding on a deeper level.

Chemical food safety hazards in circular food systems: a review

Food production has increasingly become effective but not necessarily sustainable. Transitioning toward circular production systems aiming to minimize waste and reuse materials is one of the means to obtain a more sustainable food production system. However, such a circular food production system can also lead to the accumulation and recirculation of chemical hazards. A literature review was performed to identify potential chemical hazards related to the use of edible and non-edible resources in agriculture and horticulture, and edible plant and animal by-products in feed production. The review revealed that limited information was available on the chemical hazards that could occur when reusing crop residues in circular agriculture. Frequently mentioned hazards present in edible and non-edible resources are heavy metals, process and environmental contaminants, pesticides and pharmaceuticals. For feed, natural toxins and pharmaceutical residues are of potential concern. Studies, furthermore, indicated that plants are capable of taking up chemical hazards when grown on contaminated soil. The presence of chemical hazards in manure, sewage sludge, crop residues, and animal by-products may lead to accumulation in a circular food production system. Therefore, it is relevant to identify these hazards prior to application in food production and, if needed, take precautionary measures to prevent food safety risks.

Integrated Fertilizers Synergistically Bolster Temperate Soybean Growth, Yield, and Oil Content

For ensuring food security and imparting sustainability to modern commercial-oriented and highly intensive temperate farming systems, organic wastes from poultry and dairy industries constitute biologically viable strategy to improve crops productivity under changing climate. A field trial was undertaken to appraise the impact of broiler litter (BL = 5 tons ha−1), farm yard slurry (FYS = 10 tons ha−1), and chemical fertilizers including di-ammonium phosphate (DAP = 60 kg ha−1) and single super phosphate (SSP = 60 kg ha−1) applied solely and in conjunction with each other, along with a control treatment (NM). The synergistic fertilization regime encompassing BL+DAP triggered the vegetative growth of soybean as indicated by taller plants having thicker stems and higher leaf area per plant compared to NM. In addition, this fertilization management system improved reproductive yield attributes including pods number and 100-seeds weight which maximized the seed yield, harvest index, seed oil content, and biological yield by 66%, 5%, 31%, and 23% respectively than NM. Moreover, this fertilizers combination was followed by SSP + BL, while BL performed better than FYS and DAP remained superior to SSP. Furthermore, the correlation analyses indicated moderately stronger direct association of seed yield with vegetative growth traits and highly stronger linear relationship with reproductive yield attributes. Thus, co-application of broiler litter (5 tons ha−1) with reduced doses of DAP (60 kg ha−1) might be recommended to temperate soybean growers having access to poultry wastes.

Soybean herbage yield, nutritional value and profitability under integrated manures management

Organic manures are more preferred and environmentally friendly than chemical fertilizers for minimally contaminating soil, water and environmental resources, but the determination of right source of organic manures continues to remain an unexplored aspect. Considering the important issue, a multi-year field trial was carried out to determine the response of forage soybean to four sources of nutrients such as chemical fertilizers (IF), poultry litter (PL), bovine's farm yard slurry (BFYS) and sewage sludge (SS) and their seven binary combinations (PL+BFYS, PL+SS, PL+IF, BFYS+SS, BFYS+IF, SS+IF and PL+BFYS+SS). Supplementation of organic manures with mineral fertilizers remained superior to their sole application, particularly BFYS + IF was found significantly (p≤0.05) superior for yielding the highest fresh biomass (23.9, 26.4 and 25.7 t ha-1) with improved nutritional quality. The same combination of integrated fertilizer management also recorded higher sustainability as per sustainable forage yield index along with the highest net income and the benefit-cost ratio. PL and SS applied in conjunction with IF performed better than sole or binary application of organic manures. Therefore, BFYS + IF may be recommended for adoption to produce comparable forage yield and nutritional quality of soybean along with reducing dependency on chemical fertilizers.

Influence of Biochar Derived Nitrogen on Cadmium Removal by Ryegrass in a Contaminated Soil

Little is known about the effect of nitrogen (N) application via biochar on the removal of trace elements by crops, and the effects with chemical fertilizers are inconsistent. We determined, from a previous study, the influence of increased N addition via biochars produced from switchgrass (SGB) and poultry litter (PLB) on cadmium (Cd) removal by ryegrass. The biochar rates of 0, 0.5, 1, 2, and 4% w/w were applied to a Cd-contaminated soil before seeding in a potting experiment with a complete randomized block design (CRBD). Ryegrass yield and N and Cd removed by harvest were strongly related (p < 0.05). The ryegrass yields increased up to 1% of PLB, and Cd removal was also the highest at 1% of PLB. The biomass of ryegrass roots increased with Cd accumulation (p < 0.05). Overall, the Cd transfer factor (TF) from ryegrass roots to shoots increased when up to 206 ± 38 kg N ha−1 was removed in ryegrass shoots (p < 0.0001). The application of PLB up to 1% might be a viable option since it is a practical rate for handling operations requiring less volume of material than SGB. Additionally, the Cd concentration in the aboveground forage remained acceptable for grazing cattle. Future studies are encouraged to evaluate different sources of N fertilizers affecting Cd uptake on cash crops.