Combined effects of biochar and chicken manure on maize (Zea mays L.) growth, lead uptake and soil enzyme activities under lead stress

Impacts of poultry manure and biochar amendments on the nutrients in sweet potato leaves and the minerals in the storage roots

Poultry manure (PM) has demonstrated its potential to enhance crop nutritional quality. Nevertheless, there remains a dearth of knowledge regarding its synergistic effects when combined with wood biochar (B) on the nutrient concentrations in sweet potato leaves (Ipomoea batatas L.) and the mineral content stored in sweet potato storage roots. Hence, a two-year field trial was undertaken during the 2019 and 2020 cropping seasons in southwestern Nigeria, spanning two locations (Owo-site A and Obasooto-site B), to jointly apply poultry manure and wood biochar as soil amendments aimed at enhancing the nutritional quality of sweet potato crop. Each year, the experiment involved different combinations of poultry manure at rates of 0, 5.0, and 10.0 t ha-1 and biochar at rates of 0, 10.0, 20.0, and 30.0 t ha-1, organized in a 3 × 4 factorial layout. The results of the present study demonstrated that the individual application of poultry manure (PM), biochar (B), or their combination had a significant positive impact on the nutrient composition of sweet potato leaves and minerals stored in the sweet potato storage roots, with notable synergistic effects between poultry manure and biochar (PM × B) in enhancing these parameters. This highlights the potential of biochar to enhance the efficiency of poultry manure utilization and improve nutrient utilization from poultry manure. The highest application rate of poultry manure at 10.0 t ha-1 and biochar at 30.0 t ha-1 (PM10 + B30), resulted in the highest leaf nutrient concentrations and mineral composition compared to other treatments at both sites. Averaged over two years, the highest application rate of poultry manure at 10.0 t ha-1 and biochar at 30.0 t ha-1 (PM10 + B30) significantly increased sweet potato leaf nutrient concentrations: nitrogen by 88.2%, phosphorus by 416.7%, potassium by 123.8%, calcium by 927.3%, and magnesium by 333.3%, compared to those in the control (PM0 + B0). The same treatment increased the concentration of sweet potato root storage minerals: phosphorus by 152.5%, potassium by 77.4%, calcium by 205.5%, magnesium by 294.6%, iron by 268.4%, zinc by 228.6%, and sodium by 433.3%, compared to the control. The highest application rate of poultry manure at 10.0 t ha-1 and biochar at 30.0 t ha-1 yielded the highest economic profitability in terms of gross margin (44,034 US$ ha-1), net return (30,038 US$ ha-1) and return rate or value-to-cost ratio (VCR) (263). The results suggested that the application of poultry manure at 10 t ha-1 and biochar at 30 t ha-1 is economically profitable in the study areas and under similar agroecological zones and soil conditions.

Arsenic fractionation and speciation in different textured soils supplied with farmyard manure and accumulation by sunflower under alkaline calcareous conditions

Arsenic (As) is a naturally occurring element that is found in soil, water, and rocks. However, it can also be released into the environment through human activities. Arsenic is considered an environmental hazard because it is toxic to humans and animals and can cause serious health problems. Additionally, As-contaminated soil can limit plant growth and reduce crop yields, leading to economic losses for farmers. So, decreasing metal/metalloid solubility in soil by synthetic and organic amendments leads to better crop productivity on contaminated soils. The current study aimed to evaluate farmyard manure (FYM)-mediated changes in soil arsenic (As) behavior, and subsequent effects on achene yield of sunflower. Treatment plan comprised of two As levels, i.e., As-60 (60 mg kg-1) and As-120 (120 mg kg-1), four FYM levels (0, 20, 35, and 50 g kg-1), three textural types (sandy, loamy and clayey), and replicated thrice. Seven As fractions including water soluble-As (WS-As), labile-As (L-As), calcium-bound As (Ca-As), aluminum-bound As (Al-As), iron-bound As (Fe-As), organic-matter-bound As (OM-As), and residual-As (R-As) were determined which differed significantly (P ≤ 0.05) with FYM and soil texture. FYM supplementation decreased WS-As, L-As, Ca-As, and Al-As while increased Fe-As, OM-As, and R-As. The immobilizing effect of FYM increased with increasing its rate of application, and maximum effect was found in clayey soil. As speciation in soil also significantly (P ≤ 0.05) affected by FYM and soil texture, with a reduction in arsenate while increase in arsenite, mono-methyl arsenate, and di-methyl arsenate with increasing the rate of FYM supplementation. Bioaccumulation factor reduced with FYM addition, and highest reduction of 38.65 and 42.13% in sandy, 34.24 and 36.26% in loamy while 29.16 and 35.10% in clayey soils at As-60 and As-120, respectively, by 50 g kg-1 FYM compared with respective As treatments without FYM. As accumulation in plant parts was significantly (P ≤ 0.05) reduced by FYM with the subsequent improvement in achene yield.

Compost with spent mushroom substrate and chicken manure enhances rice seedling quality and reduces soil-borne pathogens

Using cultivated soils for rice seedlings can reduce the sustainability of arable land and thus giving negative impacts to food production. As a substitute, spent mushroom compost (SMC), which has high water-holding capacity and nutrient content, shows great potentials. To determine the impacts of the proportion of SMC and paddy soil on seedling quality, rhizosphere microbial characteristics, and fungal pathogens in rice seedling substrates, we conducted a 21-day pot experiment for rice seedling under five treatments: CK, 100% paddy soil; R1, 20% SMC and 80% paddy soil; R2, 50% SMC and 50% paddy soil; R3, 80% SMC and 20% paddy soil; and R4, 100% SMC. The results showed that incorporating SMC into the substrate, especially at 50% volume (R2), increased seedling growth and vitality at the seedling growth stage without external fertilization. Moreover, the SMC amendment increased microbial activity and promoted rice seedling recruitment of plant growth-promoting rhizobacteria (PGPR) and fungi (PGPF). In addition, using SMC significantly reduced the abundance of pathogenic fungi, especially Magnaporthe grisea. Overall, the multi-faceted benefits exhibit the strong possibilities of using SMC in sustainable rice productions.

Heavy metal stabilization remediation in polluted soils with stabilizing materials: a review

The remediation of soil contaminated by heavy metals has long been a concern of academics. This is due to the fact that heavy metals discharged into the environment as a result of natural and anthropogenic activities may have detrimental consequences for human health, the ecological environment, the economy, and society. Metal stabilization has received considerable attention and has shown to be a promising soil remediation option among the several techniques for the remediation of heavy metal-contaminated soils. This review discusses various stabilizing materials, including inorganic materials like clay minerals, phosphorus-containing materials, calcium silicon materials, metals, and metal oxides, as well as organic materials like manure, municipal solid waste, and biochar, for the remediation of heavy metal-contaminated soils. Through diverse remediation processes such as adsorption, complexation, precipitation, and redox reactions, these additives efficiently limit the biological effectiveness of heavy metals in soils. It should also be emphasized that the effectiveness of metal stabilization is influenced by soil pH, organic matter content, amendment type and dosage, heavy metal species and contamination level, and plant variety. Furthermore, a comprehensive overview of the methods for evaluating the effectiveness of heavy metal stabilization based on soil physicochemical properties, heavy metal morphology, and bioactivity has also been provided. At the same time, it is critical to assess the stability and timeliness of the heavy metals' long-term remedial effect. Finally, the priority should be on developing novel, efficient, environmentally friendly, and economically feasible stabilizing agents, as well as establishing a systematic assessment method and criteria for analyzing their long-term effects.

Impacted Application of Water-Hyacinth-Derived Biochar and Organic Manures on Soil Properties and Barley Growth

The biochar application can improve the physiochemical properties of both sandy and clayey loam soils and is considered a potential adaptation tool toward climate change. Therefore, the current study is novel in combining water-hyacinth-derived biochar with organic manures as a suggested effective way of treating the soil with biochar under arid and semiarid conditions. Water hyacinth weeds were slow pyrolyzed at a temperature of 300 °C, which resulted in nonalkaline biochar with a pH value of 6.31, which is suitable for alkaline soils. A pot experiment was established to study the impact of the solo application of nonalkaline water-hyacinth-derived biochar (WHB) and its combined application with farmyard (WHB/FM) and poultry manure (WHB/PM) at a rate of 1.5 and 3%, respectively, on some chemical and physical properties of sandy and clay loam soils and some barley’s growth parameters. WHB, WHB/FM, and WHB/PM significantly affected the soil pH at different application rates (1.5 and 3%) in sandy soil. A considerable alteration in water-stable aggregates (WSA), dispersion ratio (DR), available water content (AWC), and cation ratio of soil structural stability (CROSS) index resulted from combining manures (FM and PM) with biochar better than the solo application of biochar. WHB/PM treatments had a superior effect in improving barley’s growth. Relative increases were by 37.3 and 11.0% in plant height and by 61.6 and 28.5% in the dry matter in sandy and clayey loam soils, respectively. Under the conditions of this study, we can conclude that treating the soil with WHB/PM at a rate of 1.5 and 3% is the most effective application. The current study may have a vital role in Egyptian agriculture sustainability by enhancing the soil characteristics of the old agricultural and the newly reclaimed lands.

Acid-Modified Biochar Impacts on Soil Properties and Biochemical Characteristics of Crops Grown in Saline-Sodic Soils

Soil salinity and sodicity is a potential soil risk and a major reason for reduced soil productivity in many areas of the world. This study was conducted to investigate the effect of different biochar raw materials and the effects of acid-modified biochar on alleviating abiotic stresses from saline-sodic soil and its effect on biochemical properties of maize and wheat productivity. A field experiment was conducted as a randomized complete block design during the seasons of 2019/2020, with five treatments and three replicates: untreated soil (CK), rice straw biochar (RSB), cotton stalk biochar (CSB), rice straw-modified biochar (RSMB), and cotton stalk-modified biochar (CSMB). FTIR and X-ray diffraction patterns indicated that acid modification of biochar has potential effects for improving its properties via porous functions, surface functional groups and mineral compositions. The CSMB treatment enhanced the soil’s physical and chemical properties and porosity via EC, ESP, CEC, SOC and BD by 28.79%, 20.95%, 11.49%, 9.09%, 11.51% and 12.68% in the upper 0–20 cm, respectively, compared to the initial properties after the second season. Soil-available N, P and K increased with modified biochar treatments compared to original biochar types. Data showed increases in grain/straw yield with CSMB amendments by 34.15% and 29.82% for maize and 25.11% and 15.03% for wheat plants, respectively, compared to the control. Total N, P and K contents in both maize and wheat plants increased significantly with biochar application. CSMB recorded the highest accumulations of proline contents and SOD, POD and CAT antioxidant enzyme activity. These results suggest that the acid-modified biochar can be considered an eco-friendly, cheaper and effective choice in alleviating abiotic stresses from saline-sodic soil and positively effects maize and wheat productivity.

Calcium-Rich Biochar Stimulates Salt Resistance in Pearl Millet (Pennisetum glaucum L.) Plants by Improving Soil Quality and Enhancing the Antioxidant Defense

Shrimp waste is rich in organic compounds and essential plant nutrients, e.g., calcium (Ca), and converting these wastes to organic fertilizer is important for environmental preservation and to achieve sustainable agricultural management. In the current study, Ca-rich biochar was prepared from shrimp wastes (SWB) by pyrolysis at 300 °C. We hypothesized that the Ca-rich biochar will help in solving the problem of plant growth in saline soil by reducing sodium (Na) uptake and mitigating oxidative stress. The current study aimed to investigate the effect of SWB on the quality of saline sandy soil and the mechanism of salt resistance in pearl millet (Pennisetum glaucum L.). Pearl millet plants were planted in saline sandy soil (10 dS m^-1) in wooden boxes (1.3 × 0.8 m size and 0.4 m height), and 5 doses (0, 1.0, 1.5, 2.0, and 2.5% (w/w)) of SWB were added. SWB application increased the soil quality and nutrient uptake by pearl millet plants. The highest rate of SWB increased the soil microbial biomass carbon and the activity of dehydrogenase enzyme by 43 and 47% compared to the control soil. SWB application reduced the uptake of sodium (Na⁺) and chloride (Cl^-) and increased the K/Na ratio in the leaf tissues. SWB addition significantly increased the activity of antioxidant enzymes, e.g., ascorbate peroxidase (APX), polyphenol oxidase (PPO), and pyrogallol peroxidases (PPX). The application of 2.5% SWB to the saline soil increased the soluble carbohydrates and proline in plant leaves by 75 and 60%, respectively, and reduced the malondialdehyde (MDA) by 32% compared to the control. SWB enhanced the antioxidant defense and mitigated oxidative stress by improving the synthesis of osmoprotectants, e.g., soluble carbohydrates and proline. Sandy saline soils in arid and semiarid areas suffer greatly from low organic matter contents, which reduces the soil quality and increases the risk of salt during plant growth. The high organic matter and calcium content (30%) in the shrimp waste-derived biochar improved the quality of the saline sandy soil, reduced the uptake of toxic salts, and increased the quality of the forage material. The addition of recycled shrimp waste to saline low-fertility soils improves soil productivity and is safe for soil health.