Biochar reduced soil extractable Cd but increased its accumulation in rice (Oryza sativa L.) cultivated on contaminated soils

Purpose

This study focused on the effects and mechanisms of biochar amendment to Cd-contaminated soil on the uptake and translocation of Cd by rice under flooding conditions.

Materials and methods

Pot and batch experiments were conducted using Cd-contaminated soil collected from a field near an ore mining area and a cultivar of Oryza sativa ssp. indica. Biochar derived from rice straw under anaerobic conditions at 500 °C for 2 h was mixed with the soil at the rate of 0, 2.5, and 5%.

Results and discussion

The application of 5% biochar reduced CaCl₂-extractable soil Cd by 34% but increased Cd concentration in brown rice by 451%. Biochar amendment decreased water-soluble Fe²⁺ in soils and formation of Fe plaques on roots and weakened the Fe²⁺-Cd²⁺ competition at adsorption sites on the root surface. Biochar increased water-soluble Cd in the soil and consequently Cd uptake by rice roots by releasing water-soluble Cl^?. Biochar application also reduced the proportion of cell wall-bound Cd in the root, which caused easier Cd translocation from the cortex to the stele in the root and up to the shoot.

Conclusions

Rice straw biochar (with high concentration of water-soluble Cl^?) reduced CaCl₂-extractable soil Cd but increased Cd concentration in rice under flooding condition.

     

Improvement of physical and hydraulic properties of desert soil with amendment of different biochars

Purpose

The objective of this study was to investigate the effects of amendment of different biochars on the physical and hydraulic properties of desert soil.

Materials and methods

Biochars were produced with woodchip, rice straw, and dairy manure at temperatures of 300 and 700 °C, respectively. Each biochar at 5% (w/w) was mixed with desert soil, and the mixtures were incubated for 120 days.

Results and discussion

The different biochar treatments greatly reduced soil bulk density and saturated hydraulic conductivity. Especially the rice straw biochar addition resulted in the lowest saturated hydraulic conductivities among the treatments. Biochar addition significantly increased water retention of desert soil at any suction. At the same suction and experimental time, the treatment with the rice straw biochar produced at the lower temperature resulted in higher water content than the other treatments. The biochar additions slightly enhanced formation of soil macro-aggregates in the early experimental time. However, the aggregate contents gradually decreased with time due to the lack of effective binding agents (e.g., soil organic matter and clay minerals).

Conclusions

The changes of hydraulic properties of desert soil were attributable to the biochar properties. The higher fine particle content, porosity, and surface hydrophilicity of rice straw biochars were the most beneficial properties to increase soil water retention and to reduce water flow in the desert soil. The improvement of hydraulic properties by biochar addition may provide a potential solution to combat desertification.

     

The amelioration effects of low temperature biochar generated from nine crop residues on an acidic Ultisol

Biochar was prepared using a low temperature pyrolysis method from nine plant materials including non‐leguminous straw from canola, wheat, corn, rice and rice hull and leguminous straw from soybean, peanut, faba bean and mung bean. Soil pH increased during incubation of the soil with all nine biochar samples added at 10 g/kg. The biochar from legume materials resulted in greater increases in soil pH than from non‐legume materials. The addition of biochar also increased exchangeable base cations, effective cation exchange capacity, and base saturation, whereas soil exchangeable Al and exchangeable acidity decreased as expected. The liming effects of the biochar samples on soil acidity correlated with alkalinity with a close linear correlation between soil pH and biochar alkalinity (R² = 0.95). Therefore, biochar alkalinity is a key factor in controlling the liming effect on acid soils. The incorporation of biochar from crop residues, especially from leguminous plants, can both correct soil acidity and improve soil fertility.     

Rice straw biochar amended soil improves wheat productivity and accumulated phosphorus in grain

Abstract

Biochar is a pyrolyzed biomass produced under limited oxygen or oxygen absent conditions. Few investigations have been conducted to determine the combined effect of biochar with chemical fertilizer on growth, yield and nutrient distribution pattern in root, shoot and grain in wheat as well as changes in soil physiochemical properties. This research was designed to study the combined effect of chemical fertilizer and rice straw-derived biochar on soil physio-chemical properties, growth, yield and nutrient distribution pattern within wheat plant tissue and grain. Results showed that rice straw biochar caused a significant decrease in soil pH and increase in soil organic matter as well as nutrients like total nitrogen (TN), potassium (K), magnesium (Mg) and boron (B) due to incubation. Result also showed that root biomass and straw did not differ between Bangladesh Agricultural Research Council (BARC) and ½ BARC?+?rice straw biochar treatment. Similarly, thousand grain weight and grain yield did not differ between the same treatments. The phosphorus concentration in wheat grain was highest in ½ BARC?+?rice straw biochar as compared to other treatments. The use of rice straw biochar in addition to the chemical fertilizers in wheat production systems is an economically feasible and practical nutrient management practice. Our findings urged that reduction of chemical fertilizer application is possible with supplementation of rice straw biochar.     

黄土旱塬长期施磷对土壤磷素空间分布及有效性的影响

对黄土旱塬定位施肥20年后土壤中不同磷素形态在土层中的空间分布及有效性进行了研究。结果表明,在不同施磷水平上,磷素在土壤表层发生累积。随着磷肥用量的增加,表层的全磷和有效磷的含量逐渐增加;而在下层土壤中虽有微量增加,但增幅不明显。说明长期合理施用磷肥可显著扩大土壤中的有效磷库。黄土旱塬区长期定位试验土壤表层中无机磷以CaP为主,占无机磷总量的80 % 以上。随着施磷量的增加,无机磷组分Ca2P、Ca8P、AlP和FeP在土壤中的含量总体上都呈增加的趋势。通过有效磷与无机磷各组分的相关性分析及通径分析看出,Ca2P和Ca8P可称为有效磷源,OP与Ca10P为潜在磷源,而AlP和FeP介于二者之间。其中,FeP主要是通过影响其它组分而间接影响有效磷的含量。     

Potentially hazardous element accumulation in rice tissues and their availability in soil systems after biochar amendments

Purpose

Biochar has shown to be a great product to control the bioavailability of potentially hazardous elements (PHE) in contaminated soils. Despite the advantages associated with the application of biochar in agricultural soils, relatively few studies have focused on the effects of biochar amendments on soil chemical properties, accumulation of arsenic, cadmium, zinc, and lead in rice tissues, and their availability in soil systems.

Materials and methods

The field experiment was conducted at the paddy soils in Hunan Province, China. The soil texture was sandy clay loam. Wheat-derived biochar was applied once to the experimental plots at the rates of 0, 10, 20, 30 and 40 t ha^?1, and referenced as A0, A10, A20, A30, and A40, respectively. For PHE determination, soil samples and plant samples were digested with a mixed solution of HCl:HNO₃ (4:1, V:V) and HCl:HClO₄ (4:1, V:V), respectively, and the arsenic, cadmium, zinc, and lead in the digest solution were measured by ICP-MS (Thermo Fisher Scientific, USA). The soil available fraction of PHE (arsenic, cadmium, zinc, and lead) was extracted by diethylenetriamine pentaacetic acid (DTPA) and measured by inductively ICP-MS.

Results and discussion

Biochar amendment increased chemical properties of soil organic matter, pH, electrical conductivity, cation exchange capacity, nitrate nitrogen, and available phosphorus. Soil DTPA extractable arsenic, cadmium, zinc, and lead concentrations were significantly reduced. Arsenic, cadmium, zinc, and lead in rice shoots, and arsenic, cadmium, and zinc in roots significantly decreased after amendment. Concentrations in rice tissues positively and negatively correlated with the soil available fraction of PHE and soil chemical properties, respectively. Soil electrical conductivity negatively correlated with the soil available fraction of PHE. Concentrations of arsenic, zinc, cadmium, and lead in rice roots declined relative to increases of cation exchange capacity (arsenic, zinc), available phosphorus (cadmium), and nitric nitrogen (lead) content. Similar relationships were observed between cation exchange capacity and PHE in shoots.

Conclusions

Biochar creates avoidance of PHE through regulating chemical properties through biochar sorption capacity. Cation exchange capacity, available phosphorus, and nitric nitrogen were the principle factors affecting roots uptake of arsenic, zinc, cadmium, and lead. Biochar soluble salts could decline availability of metals/metalloids in soils through precipitation. Wheat-derived biochar application is an alternative safe product to immobilize PHE in rice paddy soils by restricting the risk of PHE.

     

Effects of crop‐straw biochar on crop growth and soil fertility over a wheat‐millet rotation in soils of China

We conducted a pot experiment using a wheat‐millet rotation to examine the effects of two successive rice‐straw biochar applications on crop growth and soil properties in acidic oxisols and alkaline cambosols from China. Biochar was incorporated into soil at rates of 0, 2.25 or 22.5 Mg/ha at the beginning of each crop season with identical applications of NPK fertilizer. In the oxisols, the largest biochar treatment enhanced soil pH and cation exchange capacity, decreased soil bulk density, improved soil P, K, Ca and Mg availability and enhanced their uptake, and increased wheat and millet yields by 157 and 150% for wheat grain and straw, respectively, and 72.6% for millet straw. In the cambosols, biochar treatment decreased soil bulk density, improved P and K availability, increased N, P and K uptake by crops and increased wheat and millet straw yields by 19.6 and 60.6%, respectively. Total soil organic carbon increased in response to successive biochar applications over the rotation. No difference in water‐soluble organic carbon was recorded between biochar‐treated and control soils. Converting straw to biochar and treating soils with successive applications may be a viable option for improving soil quality, sequestering carbon and utilizing straw resources in China.     

Short-term effects of organo-mineral enriched biochar fertiliser on ginger yield and nutrient cycling

Purpose

Biochar has agronomic potential but currently is too expensive for widespread adoption. New methodologies are emerging to reduce the cost such as enriching biochar with nutrients that match crops and soil requirements. However, the effects of biochar-based fertilisers on plant yield and soil nutrient availability have not been widely examined. This study investigated the effects of a novel organo-mineral biochar fertiliser in comparison to organic and commercial biochar fertiliser on ginger (Zingiber officinale Canton).

Materials and methods

There were four treatments: (1) commercial organic fertiliser (5 t ha^?1), as the control; (2) commercial biochar-based fertiliser (5 t ha^?1); (3) organo-mineral biochar fertiliser at low rate (3 t ha^?1); and (4) organo-mineral biochar fertiliser at high rate (7.5 t ha^?1). A replicated pot trial was established with black dermosol soil and ten replicate pots for each treatment. Ginger was planted and grown for 30 weeks. Plant growth, biomass, foliar nutrients and water extractable soil nutrients including phosphorus (P), potassium (K) and calcium (Ca) were examined.

Results and discussion

High rate organo-mineral biochar fertiliser increased soil P and K availability at week 30 (harvest) after planting, compared to all other treatments and low rate organo-mineral biochar fertiliser performed similarly to the organic control for P and K. High rate organo-mineral biochar fertiliser increased total foliar nutrient content at week 30 in P, K and Ca compared to commercial biochar fertiliser. High rate organo-mineral biochar fertiliser improved the commercial value of ginger (+?36%) due to a shift in the proportion of higher grade rhizomes. Low rate organo-mineral biochar fertiliser plants displayed similar yield, total dry and aboveground biomass to commercial organic fertiliser. Commercial biochar fertiliser had significantly lower biomass measures compared with other treatments as the rate applied had lower nutrient concentrations.

Conclusions

Our results show organo-mineral biochar fertilisers could be substituted for commercial organic fertilisers at low rates to maintain similar yield or applied at high rates to increase commercial value where economically feasible.

     

The Impact of Woody Biochar on Microbial Processes in Conventionally and Organically Managed Arable soils

ABSTRACT

Although environmental impacts of biochar are well characterized, impacts on soil quality, nutrient availability and crop productivity, still remain a challenge due to the diverse response of different soil types to different types of biochar, namely those obtained at low temperature. The impact of an alkaline woody biochar (two doses 5% and 10%) obtained at 280°C, on soil enzyme activity, soil microbial respiration rate, mineral nitrogen (N) availability and ammonia volatilization was studied in one conventionally and one organically managed soils, with and without the addition of urea or composted farmyard manure. Biochar additions had different effects on soil enzyme activity in both soils, suggesting lower decomposing microbial activity processes promoted by biochar. Both soils showed a similar decreasing trend regarding soil respiration rates for all treatments, and significant relationships were observed between the treatments with different rates of applied biochar, but not constant for the entire incubation period. Urea application increased soil mineral N concentrations, especially nitrate concentrations when biochar was applied as well. Biochar decreased ammonia volatilization from conventionally managed soil fertilized with urea, but did not have a significant effect when compost was added to the organically managed soil. Biochar altered microbial behavior in soil, and was affected by previous soil management. So, the impact of biochar produced at low temperatures on soil biological processes is similar to those obtained at high temperature, thus proving that there is no need to increase the energy expenditure to produce biochar, to obtain a good product.     

Biochar amendment of chromium-polluted paddy soil suppresses greenhouse gas emissions and decreases chromium uptake by rice grain

Purpose

Soil chromium (Cr) pollution has received substantial attention owing to related food chain health risks and possible promotion of greenhouse gas (GHG) emissions. The aim of the present study was to develop a promising remediation technology to alleviate Cr bioavailability and decrease GHG emissions in Cr-polluted paddy soil.

Materials and methods

We investigated the potential role of biochar amendment in decreasing soil CO₂, CH₄, and N₂O emissions, as well in reducing Cr uptake by rice grains at application rates of 0 t ha^?1 (CK), 20 t ha^?1 (BC20), and 40 t ha^?1 (BC40) in Cr-polluted paddy soil in southeastern China. In addition, the soil aggregate size distribution, soil organic carbon (SOC) concentration of soil aggregates, soil available Cr concentration, and rice yield were analyzed after harvesting.

Results and discussion

Biochar amendment significantly reduced CO₂, CH₄, and N₂O emission fluxes. Compared to CK, total C emissions in the BC20 and BC40 treatments decreased by 9.94% and 17.13% for CO₂-C, by 30.46% and 37.10% for CH₄-C, and by 34.24% and 37.49% for N₂O-N, respectively. Biochar amendment increased the proportion of both the 2000–200 μm and 200–20 μm size fractions in the soil aggregate distribution. Accordingly, the organic carbon concentration of these fractions increased, which increased the total SOC. Moreover, biochar amendment significantly decreased soil available Cr concentration and total Cr content of the rice grains by 33.6% and 14.81% in BC20 and 48.1% and 33.33% in BC40, respectively. Rice yield did not differ significantly between biochar amendment treatment and that of CK.

Conclusions

Biochar application reduced GHG emissions in paddy soil, which was attributed to its comprehensive effect on the soil properties, soil microbial community, and soil aggregates, as well as on the mobility of Cr. Overall, the present study demonstrates that biochar has a great potential to enhance soil carbon sequestration while reducing Cr accumulation in rice grains from Cr-polluted rice paddies.

     

生物炭固定解鸟氨酸拉乌尔菌对紫色土磷钾有效性的影响

筛选能为解鸟氨酸拉乌尔菌（Raoultella ornithinolytica,Ro）提供适宜生存空间的生物炭,探讨固定Ro的生物炭对不同性质紫色土磷（P）钾（K）有效性的影响。采用限氧裂解法分别在不同温度（300 ℃、500 ℃和700 ℃）和原材料下（玉米秆、小麦秆和稻壳）制备生物炭。利用噻唑蓝（MTT）比色法筛选固定载体,通过傅立叶变换衰减全反射红外光谱法（ATR-FTIR）表征其性能和结构;采用室内土培试验探讨单施生物炭（BC）、Ro及固定Ro的生物炭（Ro-BC）对不同性质紫色土速效磷钾的影响。MTT结果表明,以热解温度500 ℃的玉米秸秆炭（MSC500）为最佳载体;红外光谱结果显示,500 ℃玉米秸秆炭表面官能团的C=C和－OH的伸缩振动峰较明显,C－O－C键伸缩振动峰加宽变深;室内培养试验表明,施入Ro和Ro-BC均可显著提高酸性、中性和石灰性紫色土速效磷、速效钾含量和细菌数量。以Ro-BC对土壤速效磷和细菌数量的提升效果最好,提升效果分别达61.1% ~ 276.3%和22.8% ~ 82.5%。但培养至168 h时,速效磷出现下降趋势;对速效钾而言,酸性紫色土以Ro处理对其提升效果最好（46.3%）,中性和石灰性紫色土则以Ro-BC处理提升效果最好（29.8%和71.23%）,针对不同Ro筛选适宜的固定载体可提高Ro菌株活性,改善土壤微环境,进而有助于提高土壤磷钾有效性。     

Rice-residue biochar influences phosphorus availability in soil with contrasting P status

ABSTRACT

Thermo-chemical conversion of crop residues to produce biochar is an emerging strategy in the context of sustainable phosphorous (P) use and residue management. An incubation study for 90 d was conducted to investigate the effects of rice-residue biochar (0, 10, 20 and 40 g kg^?1) in combination with inorganic-P (KH₂PO₄) (0, 25 and 50 mg kg^?1) on phosphorous availability in medium- and high-P status soils. Increasing biochar addition rates alone or in combination with inorganic-P resulted in a significant increase in P pools, i.e. plant available P or Olsen-P (from 8 to 132 mg kg^?1 in medium-P and 15 to 160 mg kg^?1 in high-P soils), microbial biomass P and various mineral-bound inorganic-P fractions in the order (Ca-P > organic-P > Al-P > loosely held/soluble-P > Fe-P > reductant soluble-P). Further, lower phosphatase activity (19–50%) with increasing rates of biochar addition in both soils elucidates the ability of biochar to act as a long-term source of available P in the experimental soils. The results demonstrate that rice-residue biochar can directly or indirectly enhance the status of available P in soils and hence can be used as a beneficial amendment to meet the crop P demand.     

Performance of biochar derived from Cymbopogon winterianus waste at two temperatures on soil properties and growth of Bacopa monneri

ABSTRACT

The present study aimed to evaluate the effect of biochar derived from the distilled waste of Cymbopogon winterianus at two different pyrolysis temperatures (450°C and 850°C) on the chemical and biological properties of sandy loamy soil (SLS) and its subsequent impact on plant growth. Pot experiments utilizing Bacopa monnieri were performed in a greenhouse with four different application rates of biochar (2%, 4%, 6%, and 8% (w/w)) for 120 days. Biochar induced alterations in soil properties (nutrients, enzymes, and microbes) and plant responses (yield, biocide and antioxidant content) to biochar addition were measured. Biochar application, notably improved the soil carbon, cation exchange capacity, and the availability of NH₄ ⁺ and phosphorus. Initially, biochar produced at the lower temperature had more effect on the available nitrogen, phosphorus, soil enzymatic properties, and plant biomass growth. After 120 days, the pyrolysis temperature had only a marginal influence on biochar-induced effects on soil pH, WHC, and soil enzymatic activities. Our results suggest that C. winterianus derived biochar amendment leads to an overall amelioration of soil fertility and plant growth improvement. In specific biochar produced at lower temperatures (450°C) was more effective for improvement of plant biomass and soil characteristics.     

Positive effects of biochar application and Rhizophagus irregularis inoculation on mycorrhizal colonization, rice seedlings and phosphorus cycling in paddy soils

Phosphorus (P) is an essential element for plant growth but is often limiting in ecosystems; therefore, improving the P fertilizer use efficiency is important. Biochar and arbuscular mycorrhizal fungi (AMF) may enhance P cycling in paddy soils that contain high content of total P but low content of available P (AP). In this study, the effects of biochar addition and Rhizophagus irregularis inoculation on the organic and inorganic P contents and phosphatase activities in paddy soils, rice seedling growth, and AMF colonization were investigated. Compared with no biochar addition, biochar addition enhanced the percentage of spore germination at day 7, hyphal length, most probable number, and mycorrhizal colonization rate of R.irregularis by 32%, 662%, 70%, and 28% on average, respectively. Biochar and R. irregularis altered soil P cycling and availability. Biochar and R. irregularis, either individually or in combination, increased soil AP content by 2%-48%. Rice seedlings treated with biochar and R. irregularis produced greater biomass, improved root morphology, and increased nutrient uptake compared with those of the control without biochar and R. irregularis. The results suggest that combined application of biochar and R. irregularis is beneficial to rice cultivation in paddy soils with high content of total P but low content of AP.     

N2O emission mitigation and microbial activity after Biochar and Cao application in a flooded nitrate-rich vegetable soil

Adding easily decomposable organic materials into flooded nitrate-rich soils can effectively decrease the soil nitrate concentration and repair nitrate-rich soil. However, nitrate reduction is usually accompanied with an increase in N₂O emission. This study was conducted to reduce N₂O emission in a nitrate-rich vegetable soil flooded for remediation and amended with biochar. Nitrate-rich vegetable soil was placed in five treatment groups: flooding (F); flooding with rice straw (F?+?RS); flooding with rice straw and 1% biochar (F?+?RS?+?1% biochar); flooding with rice straw and 3% biochar (F?+?RS?+?3% biochar); flooding with rice straw and CaO (F?+?RS?+?CaO). Biochar and CaO reduced the N₂O emission levels relative to the F?+?RS group, with the former being more effective than the latter, achieving reduction of 40.70% (3% biochar) and 17.35% (CaO) of cumulative N₂O emission. The 3% biochar was more effective than the 1% biochar. Regression analysis showed a positive correlation between the abundance of NO reductase gene (norB) and soil N₂O emission flux. In general, biochar and CaO could effectively reduce N₂O emissions from a nitrate-rich vegetable soil during flooding remediation, duo to elevating soil pH and altering denitrifying activity. The norB gene was the most important denitrifying gene driving soil N₂O emission in the remediation.     

Effects of biochar and phosphorus fertilizer rates on soil physical properties and wheat yield on clay textured soil in middle Nile Delta of Egypt

ABSTRACT

Biochar has not been adequately used by farmers to improve the clay textured soil productivities in the world. Therefore, the objective of this study is to investigate the effect of the co-application of biochar with different rates of phosphorus (P) fertilizer on selected soil physical properties and wheat yield on clay textured soil over two growth seasons. Biochar treatments occupied the main plots at a rate of 0.0 and 10 t ha^?1, while the sub-plots were devoted to phosphorus rates at rates of 0%, 50%, 100%, and 150% of recommended P fertilizers. Biochar (10 t ha^?1) and P at different rates decreased soil bulk density significantly. Meanwhile, it increased aggregate stability, saturated hydraulic conductivity and soil water retention significantly at (p < .05), and it improved the grain yield of wheat. More grain yields in the soil treated with biochar than untreated soil under all P application rates for both years were probably caused partially by more nutrients (N, P, and K) were applied from biochar itself. Grain yield of wheat in the soil-amended biochar and P did not increase significantly between the application at 50%, 100% and 150% P. The results of this study indicate that phosphorus blends with biochar can be used to decrease the bulk density of clay textured soils and to improve crop production in these soils.     

稻壳基生物炭对生菜Cd吸收及土壤养分的影响

探讨稻壳基生物炭对Cd污染土壤上叶菜吸收Cd和土壤Cd形态的影响作用,明确稻壳基生物炭对土壤Cd污染的调控效应,可为合理利用稻壳基生物炭降低叶菜Cd含量提供参考。采用盆栽试验,研究了稻壳基生物炭在不同用量水平下对2茬生菜地上部Cd含量、土壤养分含量及Cd赋存形态的影响。结果表明,在5~25 g-kg-1用量范围内,稻壳基生物炭显著降低了2茬生菜地上部和根系Cd含量,且在最大用量25 g-kg-1时效果最好,地上部Cd含量分别比未施稻壳基生物炭的对照处理降低了19.6%和45.8%,根系Cd含量分别降低了36.8%和28.0%。在25 g-kg-1用量水平下,稻壳基生物炭对土壤p H、有效磷、速效钾及有机质含量提升效果明显,但显著降低了土壤碱解氮含量。施加稻壳基生物炭对土壤有效态Cd含量及Cd化学形态也有不同影响。随着稻壳基生物炭用量的增加,土壤NH4OAc提取态Cd含量和弱酸提取态Cd含量显著降低,在用量为25 g-kg-1时,分别比对照降低17.9%和10.4%,可还原态Cd含量无显著变化,可氧化态Cd含量呈减低趋势,残渣态Cd含量增加17.6%。因此推测,提升土壤p H、降低土壤有效态Cd含量、增加残渣态Cd含量可能是稻壳基生物炭降低生菜体内Cd含量的主要原因。稻壳基生物炭可以作为土壤改良剂,抑制Cd污染土壤上叶菜对Cd的吸收,改善土壤养分状况。     

The interactive effects of biochar and cow manure on rice growth and selected properties of salt-affected soil

Salt-affected soil induces detrimental influences on paddy rice (Oryza sativa L.) growth and ameliorating the influences could be done with organic amendments, such as animal manure and biochar. The aims of the current study are: (1) to examine the interactive effects of biochar and cow manure on rice growth and on selected properties of salt-affected soil, and (2) to identify potential mechanisms related to the amendments. Saline-sodic soil was used for a net house experiment with two experimental factors: biochar (no-biochar, rice-husk, and -straw biochar) and cow manure (with and without cow manure). Without the manure, addition of both rice-hush and – straw biochar significantly increased rice growth, whereas a combination of individual biochar with manure did not show a positive synergistic effect. The interactive effect of two factors was not significant on available P and exchangeable K concentrations, but the main effects of the two factors were significant. Biochar addition resulted in higher soil cation exchange capacity (CEC) (28.8 to 29.0 cmol_c kg^?1) than the control (25.6 cmol_c kg^?1), but manure addition did not. Improved nutrient availabilities such as P and K, as well as CEC are among the potential mechanisms accounting for the enhanced rice growth with biochar.     

Effect of Sheep Manure and Its Produced Vermicompost and Biochar on the Properties of a Calcareous Soil after Barley Harvest

ABSTRACT

Conversion of manures to vermicompost and biochar may alleviate some negative effects of manure application to soil but the efficiency of the produced vermicompost and biochar as compared to their feedstocks is not well-known. In the current investigation, we compared the effects of sheep manure and its derived vermicompost and biochar (pyrolyzed at 400°C for 4 h) on the properties of a calcareous soil that planted with five cultivars of barley (Behrokh, Khatam, Reyhaneh03, Fajr 30 and Nimrooz) for 60 days. Different soil properties and availability of nutrients and barley yield were determined after plant harvest. The biochar significantly increased barley yield rather than control (4.20 vs. 3.57 g pot^?1), but sheep manure and vermicompost had no effect on it (3.51 and 3.37 g pot^?1, respectively). Fajr 30 and Nimrooz (3.52 and 3.42 g pot^?1, respectively) had significantly lower yield than other cultivars. Biochar increased soil pH up to 8.2. Soil salinity was increased by application of all organic materials (increase to 16–36%). Cation exchange capacity (CEC) and organic matter content of soil were also increased by all organic materials application (0.4–0.9 cmol kg^?1 and 0.33–0.50%, respectively). All organic materials increased total nitrogen (N), but this increase was the highest with sheep manure application (53%). The availability of phosphorus (P) and potassium (K) was increased significantly by application of all organic materials, and this increase was the highest with biochar application (19 and 309 mg kg^?1, respectively). Biochar application had no effect on the availability of micronutrients, but application of sheep manure and vermicompost increased the availability of iron (Fe) (0.62 and 0.48 mg kg^?1, respectively) and zinc (Zn) (0.18 and 0.37 mg kg^?1, respectively). Generally, organic materials may change the status of soil nutrients via change in soil pH, organic matter content, release of nutrients, increase in soil CEC and formation of soluble complex with nutrients.     

Effects of biochar application in forest ecosystems on soil properties and greenhouse gas emissions: a review

Purpose

Forests play a critical role in terrestrial ecosystem carbon cycling and the mitigation of global climate change. Intensive forest management and global climate change have had negative impacts on the quality of forest soils via soil acidification, reduction of soil organic carbon content, deterioration of soil biological properties, and reduction of soil biodiversity. The role of biochar in improving soil properties and the mitigation of greenhouse gas (GHG) emissions has been extensively documented in agricultural soils, while the effect of biochar application on forest soils remains poorly understood. Here, we review and summarize the available literature on the effects of biochar on soil properties and GHG emissions in forest soils.

Materials and methods

This review focuses on (1) the effect of biochar application on soil physical, chemical, and microbial properties in forest ecosystems; (2) the effect of biochar application on soil GHG emissions in forest ecosystems; and (3) knowledge gaps concerning the effect of biochar application on biogeochemical and ecological processes in forest soils.

Results and discussion

Biochar application to forests generally increases soil porosity, soil moisture retention, and aggregate stability while reducing soil bulk density. In addition, it typically enhances soil chemical properties including pH, organic carbon stock, cation exchange capacity, and the concentration of available phosphorous and potassium. Further, biochar application alters microbial community structure in forest soils, while the increase of soil microbial biomass is only a short-term effect of biochar application. Biochar effects on GHG emissions have been shown to be variable as reflected in significantly decreasing soil N₂O emissions, increasing soil CH₄ uptake, and complex (negative, positive, or negligible) changes of soil CO₂ emissions. Moreover, all of the aforementioned effects are biochar-, soil-, and plant-specific.

Conclusions

The application of biochars to forest soils generally results in the improvement of soil physical, chemical, and microbial properties while also mitigating soil GHG emissions. Therefore, we propose that the application of biochar in forest soils has considerable advantages, and this is especially true for plantation soils with low fertility.