Effects of rice and corn straw biochar combined with microbial inoculant on soil health in protected vegetable production.

In order to understand the resource utilization of plant biomass, five types of biomass materials were used to produce biochar to treat wastewater containing phosphorus. The phosphorus adsorption capacity of five materials was preliminarily compared through laboratory experiments, and two materials with strong phosphorus adsorption capacity were screened out. The physicochemical characteristics of the selected biochar were analyzed using scanning electron microscopy and a BET specific surface area analyzer, and the effects of different pH values on phosphorus adsorption of the biochar were investigated. Furthermore, the phosphorus adsorption characteristics of the selected biochar were analyzed via isothermal adsorption and adsorption kinetics models. The results showed that among the five biochar materials, only rice straw and corn straw biochar had the ability to adsorb phosphorus. The Langmuir isothermal adsorption curve showed that the adsorption capacity of rice straw biochar for phosphorus in wastewater was stronger than that of corn straw biochar, and the theoretical maximum adsorption capacity was as follows:rice straw biochar (9.78 mg·g-1)>corn straw biochar (0.39 mg·g-1). The specific surface area (148.30 m2·g-1) and total pore volume (0.11 cm3·g-1) of rice straw biochar were much higher than those of corn straw biochar (8.26 m2·g-1 and 0.03 cm3·g-1, respectively), and the contents of Mg, Ca, Fe, and Al were higher in rice straw biochar. The best pH for phosphorus adsorption of rice straw biochar and corn straw biochar was acidic. In different pH ranges (3.0-11.0), the phosphorus adsorption capacity of rice straw and corn straw biochar decreased with the increase in pH. These results indicated that rice straw biochar has strong phosphorus adsorption capacity and has a better application prospect in wastewater treatment.

Properties of biochars derived from different straw at 500℃ pyrolytic temperature: Implications for their use to improving acidic soil water retention

Adsorption kinetics and isotherms of Cd2+ onto different types of biochar are studied in batch experiments. Three types of biochar (rice, wheat and corn straw biochar) and their phosphate or chitosan modified materials were used in this study. Results showed that Langmuir equation can better describe the adsorption isotherms of Cd2+ onto these biochars (r2 > 0.960). Among different types of biochars, rice straw biochar (RB) and its chitosan modified biochar (CRB) had highest adsorption capacity of Cd2+. RB, wheat straw biochar (WB) and their modified biochars were used to remediate Cd-contaminated soil. Soil pH values increased with the increasing of biochar dosage and chitosan modified biochar amended soil had the highest soil pH values. Contents of DTPA extractable Cd in soil decreased with the increase of biochar dosage and incubation time. Among different types of biochars, 5% CRB amended soil at 60 days of incubation had the lowest content of DTPA extractable Cd. This study showed that the application of modified biochars can effectively alleviate soil Cd contamination.

Soil organic carbon content affects the stability of biochar in paddy soil

This research aims to compare fresh biochar and NPK-enriched biochar and their decomposition levels and nutrient absorption efficiency in acid soil with soybean. Factorial randomized block design was used in this experiment and consisted of two factors. The first factor, biochar source, comprised four levels: B0: biochar without NPK, B1: rice straw biochar + NPK, B2: soybean straw biochar + NPK, and B3: wood biochar + NPK. The second factor, biochar enrichment, comprised four levels: D1: 0.5 tons ha<sup>-1</sup>, D2: 2.5 tons ha<sup>-1</sup>, D3: 5.0 tons ha<sup>-1</sup>, and D4: 10 tons ha<sup>-1</sup>. Each treatment was replicated three times, yielding 48 experiment units. The results showed that biochar enrichment with NPK affected the decomposition level. The percentage of increasing decomposition in enriched wood biochar (0.09%) was lower than rice (0.28%) and soybean (0.53%) straw biochar. An increase in NPK absorbance efficiency and soybean dry weight was evident in NPK-enriched biochar. The highest N absorbance efficiency occurred in wood biochar (21%), followed by soybean and rice straw biochar, respectively, while the highest P and K absorbances were found in rice straw biochar (35% and 26%, respectively), followed by wood and then soybean biochar.

Biochar is a carbon-rich solid material derived from the pyrolysis of agricultural and forest residual biomass. Previous studies have shown that biochar is suitable as an adsorbent for soil contaminants such as heavy metals and consequently reduces their bioavailability. However, the long-term effect of different biochars on metal extractability or soil health has not been assessed. Therefore, a 1-year incubation experiment was carried out to investigate the effect of biochar produced from bamboo and rice straw (at temperatures ≥500 °C) on the heavy metal (cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn)) extractability and enzyme activity (urease, catalase, and acid phosphatase) in a contaminated sandy loam paddy soil. Three rates (0, 1, and 5%) and two mesh sizes (<0.25 and <1 mm) of biochar applications were investigated. After incubation, the physicochemical properties, extractable heavy metals, available phosphorus, and enzyme activity of soil samples were analyzed. The results demonstrated that rice straw biochar significantly (P < 0.05) increased the pH, electrical conductivity, and cation exchange capacity of the soil, especially at the 5% application rate. Both bamboo and rice straw biochar significantly (P < 0.05) decreased the concentration of CaCl2-extractable heavy metals as biochar application rate increased. The heavy metal extractability was significantly (P < 0.01) correlated with pH, water-soluble organic carbon, and available phosphorus in soil. The 5% application rate of fine rice straw biochar resulted in the greatest reductions of extractable Cu and Zn, 97.3 and 62.2%, respectively. Both bamboo and rice straw biochar were more effective at decreasing extractable Cu and Pb than removing extractable Cd and Zn from the soil. Urease activity increased by 143 and 107% after the addition of 5% coarse and fine rice straw biochars, respectively. Both bamboo and rice straw biochars significantly (P < 0.05) increased catalase activity but had no significant impact on acid phosphatase activity. In conclusion, the rice straw biochar had greater potential as an amendment for reducing the bioavailability of heavy metals in soil than that of the bamboo biochar. The impact of biochar treatment on heavy metal extractability and enzyme activity varied with the biochar type, application rate, and particle size.

In order to analyse the impact of biochar in terms of reducing the bioavailability of cadmium (Cd) in soil, a study was conducted on the solidification effect of biochar on soil cadmium and its resistance to cadmium contamination in lettuce. In this study, soil which was contaminated with 10 mg/kg cadmium was used as the substrate; corn, rice, and wheat straw biochar were used as solidification and amendment materials; and lettuce (Lactuca sativa L. cv. Grand Rapids) was used as the test plant. The morphological characteristics of the biochar, soil pH, electrical conductivity, cation exchange capacity, and soil-available Cd, as well as lettuce plant height, fresh weight, and leaf Cd content, were measured and analysed. The results showed that all three types of biochar possessed distinct porous structures and functional groups such as hydroxyl, ether, and carbonyl groups. Increases in soil pH, electrical conductivity (EC), cation exchange capacity (CEC), lettuce plant height, and fresh weight were effectively promoted. Additionally, a significant reduction in the available Cd content in the soil and Cd content in lettuce leaves was observed, with the inhibitory effect becoming more pronounced as the biochar application rate increased. When 5% corn straw biochar was added (1 kg of substrate with 50 g of biochar), the best inhibitory effect on Cd contamination was observed, with a cadmium content of 4.63 mg/kg in lettuce leaves. The available Cd in the soil and the Cd content in lettuce leaves decreased by 32.00% and 49.78%, respectively, compared to the CK group (without biochar treatment). Additionally, the plant height and fresh weight of lettuce increased by 25.56% and 31.31%, respectively, compared to the CK group. This indicated that the application of straw biochar can stabilise soil Cd, reduce the availability of Cd in the soil, inhibit the transfer of Cd into lettuce, promote the growth of lettuce, and lower the ecological environmental risk of Cd. These research results can provide a theoretical basis and scientific guidance for the remediation of soil Cd contamination and the safe production of lettuce.

Two field experiments were raised at Farm of El-Sirw Agriculture Research Station, Dammitta province, Egypt through 2018 and 2019 seasons. The present study was performed to compromise the influence of rice straw biochar and other two soil amendments of rice straw compost and gypsum on rice growth and yield of three contrasting rice varieties,Giza177 (salt sensitive variety), Giza 178 (salt tolerant variety) and Giza179 new (salt tolerant variety) under saline sodic soil. The field experiments were designed in spilt plot design with four replications. The three rice varieties were scattered in the main plot, whereas the amendment treatments; control, gypsum(G), rice straw compost (RS) and rice straw biochar (RSB) were put in the subplots. The tested rice varieties were significantly different in growth parameters, yield attributes and yields in both seasons. Giza 179 as a new salt tolerant variety provided the maximum values of rice growth characteristics and most of yield contributes and yields without significant difference with Giza178 were considering yields. Applying varying soil amendments greatly improved rice growth and yields in addition to yield attributes comparing to the control treatments. Rice straw biochar surpassed significantly other two amendments, particularly in the first season, meanwhile in the second seasonthe three soil amendments were equally in increasing grain yield. Thereby, rice straw biochar could be applied each two years but rice straw compost has to apply in two successive season to get its efficiency. Two field experiments were raised at Farm of El-Sirw Agriculture Research Station, Dammitta province, Egypt through 2018 and 2019 seasons. The present study was performed to compromise the influence of rice straw biochar and other two soil amendments of rice straw compost and gypsum on rice growth and yield of three contrasting rice varieties,Giza177 (salt sensitive variety), Giza 178 (salt tolerant variety) and Giza179 new (salt tolerant variety) under saline sodic soil. The field experiments were designed in spilt plot design with four replications. The three rice varieties were scattered in the main plot, whereas the amendment treatments; control, gypsum(G), rice straw compost (RS) and rice straw biochar (RSB) were put in the subplots. The tested rice varieties were significantly different in growth parameters, yield attributes and yields in both seasons. Giza 179 as a new salt tolerant variety provided the maximum values of rice growth characteristics and most of yield contributes and yields without significant difference with Giza178 were considering yields. Applying varying soil amendments greatly improved rice growth and yields in addition to yield attributes comparing to the control treatments. Rice straw biochar surpassed significantly other two amendments, particularly in the first season, meanwhile in the second seasonthe three soil amendments were equally in increasing grain yield. Thereby, rice straw biochar could be applied each two years but rice straw compost has to apply in two successive season to get its efficiency.

Removal of Pb(II) ions from aqueous solution by manganese oxide coated rice straw biochar A low-cost and highly effective sorbent

Industrial activities can contribute to the heavy metal accumulation in soils, which could potentially threaten human health, agricultural crop productivity and the environment. This research was conducted to use metal uptake and spectroscopic analysis (X-Ray Diffraction (XRD), Energy Dispersive spectroscopy by X-rays (EDX) and Fourier Transmission Infrared Spectroscopy (FTIR) to evaluate the effect of application of both rice straw biochar and compost with different ratios on heavy metal immobilization in the canola plants grown in the contaminated soil. The results showed that the Cd, Pb, Ni and Zn uptake in the root and shoot of canola plants significantly decreased with the addition of rice straw compost (RC) and biochar (RB) to contaminated soil. The addition of 1% mixture of RC and RB gives the most effective immobilizing metals as 100% and 74.2%, reduction in Cd and Pb accumulation by canola shoots, respectively. The biochar and compost obtained from rice straw showed high carbon content, silica and a high absorption character. The use of spectroscopic analysis observed the precipitation, inner-sphere complex reaction and electrostatic attraction are the dominating mechanism for heavy metal immobilization with organic amendments. Our results indicate that the metal uptake is considered to be the effective tool to assess the efficiency of immobilizing agents on metal phyto-availability.

β-cyclodextrin functionalized biochars as novel sorbents for high-performance of Pb2+ removal.

Edible beans play a significant role in healthy dietary structures， human health， and soil improvement. Scientifically and reasonably assessing the health status of the soil where they are cultivated is crucial for achieving green， high-yield， and high-quality production. This study focused on soils from major edible bean-producing areas across the country， collecting soil samples from 0-20 cm depth and measuring 27 indicators reflecting soil physical， chemical， and biological characteristics. Principal component analysis （PCA） and network analysis （NWA） were used to obtain the minimum data set， combined with linear scoring （L） and nonlinear scoring （NL） standardization methods， as well as the integrated health index （IHI） and Nemerow quality index （NQI） integration methods， to construct eight soil health assessment methods and calculate the corresponding soil health index （SHI）. By comparing the SHI constructed from the full dataset through correlation and sensitivity analyses and combining the linear fitting results of SHI with soil organic carbon （SOC） and yield， the most suitable soil health assessment method for the major edible bean-producing areas was selected， and the soil health status was evaluated. The results indicated： ① The four SHIs （L-IHI， NL-IHI， L-NQI， and NL-NQI） based on the minimum data set obtained by NWA showed a higher correlation （r&gt;0.8） with the SHI constructed from the full dataset than those based on PCA （0.6&lt;r&lt;0.8）， better reflecting overall soil health status. ② The variation degree of the four SHIs based on NWA （60%-70%） was much higher than that of the SHI constructed from the full dataset and PCA （20%-40%）， indicating higher sensitivity for evaluating soil health in major edible bean-producing areas nationwide. ③ Among the four SHIs based on NWA， L-IHI showed the best linear fitting results with yield and SOC， indicating that NWA-L-IHI is the optimal method for evaluating soil health in major edible bean-producing areas. ④ According to the NWA-L-IHI method for evaluating soil health in major edible bean-producing areas nationwide， the results showed that the soil health level in subtropical and warm temperate regions was generally higher than that in mid-temperate regions. The soil health level in major producing areas in Yunnan and Fujian provinces was relatively high （SHI&gt;0.2）， whereas the soil health status in major producing areas in Shaanxi， Shanxi， Hebei， and Inner Mongolia provinces （autonomous regions） was relatively poor （0.05&lt;SHI&lt;0.15）. The study results clarified the soil health status in different regions， providing a scientific basis for soil management. Appropriate nutrient management， such as fertilization and providing organic cover， can address the deficiency of nitrogen， phosphorus， and micronutrients， and each province can also improve soil health by exploring locally suitable edible bean planting patterns.

Ginseng is an important cash crop. The long-term continuous cropping of ginseng causes the imbalance of soil environment and the exacerbation of soil-borne diseases, which affects the healthy development of ginseng industry. In this study, ginseng continuous cropping soil was treated with microbial inocula using broad-spectrum biocontrol microbial strain Frankia F1. Wheat straw, rice straw and corn straw were the best carrier materials for microbial inoculum. After treatment with microbial inoculum prepared with corn straw biochar, the soil pH value, organic matter, total nitrogen, available nitrogen, available phosphorus, and available potassium were increased by 11.18%, 55.43%, 33.07%, 26.70%, 16.40%, and 9.10%, the activities of soil urease, catalase and sucrase increased by 52.73%, 16.80% and 43.80%, respectively. A Metagenomics showed that after the application of microbial inoculum prepared with corn straw biochar, soil microbial OTUs, Chao1 index, Shannon index, and Simpson index increased by 19.86%, 16.05%, 28.83%, and 3.16%, respectively. Three classes (Alphaproteobacteria, Gammaproteobacteria and Sphingobacteria) were the dominant bacteria in ginseng soil, and their abundance increased by 7.87%, 9.81% and 1.24%, respectively, after treatment with microbial inoculum with corn straw biochar. Results indicated that the most effective treatment in ginseng soil would be the combined application of corn straw biochar and Frankia F1.

To compare the dynamic effects of straw and corresponding biochar on soil acidity, nutrients, and exchangeable capacity in red soil, a pot experiment was performed. The treatments included control (CK), rice straw (R1B0), rice straw biochar prepared at 350℃ (R1B1) and 550℃ (R1B2), rape stalk (R2B0), and rape stalk biochar prepared at 350℃ (R2B1) and 550℃ (R2B2). Straw at 1% and corresponding biochar were added to a strongly acidic red soil. The rice was planted as the experimental crop. Soils were collected at the seedling, tillering, filling and mature stages of rice growth, respectively. The changes in soil pH, exchangeable acidity, organic matter, nutrients (NH4+-N and NO3--N), and exchangeable cations in soils were measured. The results showed that soil pH, NH4+-N, and NO3--N concentrations decreased with the growth period of rice, while the organic matter content and cation exchange capacity (CEC) increased. Direct returning of straw and biochar could increase soil pH, organic matter content, and exchangeable cations content, and reduce the total amount of exchangeable acids. In the mature stage of rice, rice straw and rape stalk biochar at 350℃ increased the soil pH by 0.29 and 0.42, respectively, compared to the control treatment. Similarly, biochar decreased the exchangeable acidity and exchangeable Al3+ content significantly compared to the direct returning treatments of straw. The exchangeable acidity and exchangeable Al3+ contents of soils in R1B2 and R2B1 treatments decreased by 54.8% and 58.9%, respectively, compared to the control treatment. The soil organic matter (SOM) content and CEC in biochar treatments were significantly higher than those in direct returning treatments of straw. Overall, the effects of rape stalk biochar on soil properties were slightly stronger than those of rice straw. The correlation analysis showed that soil exchangeable acids had a significantly negative correlation with organic matter (R=-0.912, P<0.01), and CEC (R=-0.866, P<0.05). The CEC in soils was positively related to organic matter (R=0.833, P<0.05). Direct returning of straw and biochar applications can effectively improve soil acidity and increase nutrient contents. The effects of straw biochar on soils were stronger than the direct returning of straw in decreasing soil acidity, and increasing soil organic matter content and exchangeable capacity in acidic soils.

We analyzed the effects of rice straw biochar (RSBC) and swine manure biochar (SMBC) on N2O emission from paddy soil. The biochars were added to soil at the rates of 1% and 5% (w/w), and N2O emission, soil properties and soil enzyme activities were determined at the elongation, heading and maturation stages of rice growth. The N2O flux started within 2 h of adding the biochar, and decreased significantly thereafter during the three growth stages. The cumulative N2O emission was suppressed by 45.14–73.96% following biochar application, and 5% SMBC resulted in the lowest cumulative emission. In addition, biochar application significantly increased soil pH, soil organic carbon (SOC), NO3− levels and urease activity, and decreased soil NH4+ and nitrate reductase activity. Regression analysis indicated that cumulative N2O emission was correlated positively to NH4+, and negatively to soil pH, SOC and NO3−. SEM further revealed that biochar application weakened the denitrification process, and the NH4+ level had the most significant impact on N2O emission. Taken together, RSBC and SMBC regulated the nitrogen cycle in paddy soil and mitigated N2O emission by increasing soil pH, decreasing nitrate reductase activity and NH4+ content.