生物质炭改良土壤及对作物效应的研究进展

生物质炭是作物秸秆等有机物质在限制供氧的条件下加热而成。生物质炭具有养分含量丰富、碱性和高稳定性等特点,因此可以降低土壤酸度,有效截留土壤养分,并在一定程度上促进养分吸收而提高作物产量。本文主要综述了生物质炭制备的影响因素及其施用后对土壤理化性质、作物生长发育和养分吸收等方面的影响。由于生物质炭在国内外的研究仍处于起步阶段,研究过程中所采取的方法、所用不同来源的生物质炭以及研究的具体对象等不尽相同,研究的结果显示生物质炭在某些方面的作用仍存在不同结论。目前,生物质炭的研究多集中在表面宏观现象上,对其深入的机理研究仍较欠缺,因此,需要科技工作者的进一步探索,文章最后阐述了未来对该领域研究的一些观点。

Effects of Reduced Nitrogen Fertilization and Biochar Application on CO_2 and N_2O Emissions from a Summer Maize-Winter Wheat Rotation Field in North China

This experiment was conducted in Xinxiang, Henan from June 2013 to June 2014. Total four treatments were designed including farmers ’ common practice （F, 250 kg/hm^2）, 80% F （LF, 200 kg/hm^2）, 80% F＋biochar （LFC） and no fertilizer （CK） to measure the dynamic emissions of CO2 and N2O from a summer maize-winter wheat field by static chamber-gas chromatography method. The results showed that the soil CO2 emission was 21.8-1 022.7 mg/（m^2·h）, and was mainly influenced by soil temperature and moisture content. During the growth of summer maize, the soil CO2 emission was more significantly affected by soil moisture con-tent; and in winter wheat growing season, it was more significantly affected by soil temperature in the top 5 cm. The LF and LFC treatments significantly reduced the soil cumulative CO2 emission, especial y during the growth of winter wheat. Fertiliza-tion and irrigation were the main factors influencing the soil N2O emission. The soil N2O emission during the fertilization period accounted for 73.9%-74.5% and 40.5%-43.6% of the soil cumulative N2O emission during the summer maize-and winter wheat-growing season, respectively. The peak of emission fluxes was determined by fertilization amount, while the occurrence time of emission peak and emission re-duction effect were influenced by irrigation. The LF treatment reduced the soil cu-mulative N2O emission by 15.7%-16.8% and 18.1%-18.5% during the growth period of summer maize and winter wheat, respectively. Reduced nitrogen fertilization is an effective way for reducing N2O emission in intensive high-yielding farmland. Under a suitable nitrogen level （200 kg/hm^2）, the application of biochar showed no significant effect on the soil N2O emission in a short term. The N2O emission factors of the L and LF treatments were 0.60% and 0.56%, respectively. ln the intensive high-yield-ing farmland of North China, reducing the nitrogen application amount is an appro-priate measure to mitigate greenhouse gas emissions without crop yield loss.

Effects of Different Biochar Dosages and Types on Growth, Yield and Output Value of Flue-cured Tobacco in Hanzhong Area

[Objective] This study was to investigate the effects of different biochar dosages and trpes on growth, yield and output value of flue-cured tobacco in Hanzhong. [Methods] In May-September of 2013, Xiaonanhai Town, Nanzheng County, Hanzhong City, a field experiment was carded out to study the effects of- biochardosage and type on tobacco agronomic traits, yield and output value in each growth period. [Results] Biochar application significantly increased plant height, stem diameter and leaf size in the early growth pedod, and raised tobacco yield, output value and the proportion of high grade leaf： With the increase of biochar dosage, tobacco agronom~ traits were significantly improved, and yield, output value and proportion of high-grade tobacco leaves also increased significantly, and the highest tobacco yield and output value occurred at the dosage of 900 kg/hm2. Agronomic traits of tobacco leaves with the application of rice husk char and wheat straw char were significantly better than those with the application of peanut shell char, appli- cation of rice husk char was more conducive to the development of leaves in the vigorous pedod and stems in the squaring period, but straw char was beneficial to improvement of plant height and leaf number in the vigorous period and leaf growth in the squaring period, and application of rice husk char had the best effect on the increases of yield and output value of tobacco leaves. [Conclusion] Application of biochar is an effective measure forimproving tobacco-planting soil and promoting the growth and development of tobacco in Hanzhong, biochar application amount should be controlled at about 600-900 kg/hm2, and rice husk char is the preferred choice as soil improvement material.

Cr(Ⅲ) adsorption by sugarcane pulp residue and biochar

A batch experiment was conducted to investigate the adsorption of trivalent chromium （Cr（Ⅲ）） from aqueous solutions by sugarcane pulp residue （SPR） and biochar. The results show that Cr（Ⅲ） adsorption by SPR and biochar is highly pH-dependent and Cr（Ⅲ） adsorption amount increases with the increase of pH. The adsorption kinetics of Cr（Ⅲ） fits well with the pseudo-second-order model. The maximum Cr（Ⅲ） adsorption capacities of 15.85 mg/g and 3.43 mg/g for biochar and SPR were calculated by Langmuir model. This indicates that biochar has a larger ability for Cr（Ⅲ） adsorption than SPR. The free energy change value （AG） reveals a spontaneous sorption process of Cr（Ⅲ） onto SPR and non-spontaneous sorption process onto biochar. The entropy change （AS） and enthalpy change （AH） are found to be 66.27 J/（mol＇K） and 17.13 kJ/mol for SPR and 91.59 J/（mol-K） and 30.875 kJ/mol for biochar which further reflect an affinity of Cr（Ⅲ） onto SPR and biochar. It is suggested that biochar has potential to be an efficient adsorbent in the removal of Cr（Ⅲ） from industrial wastewater.

Heat Transfer Validation and Comparative Evaluation of Biochar Yield from Pyrolysis Cook Stove

The developing world still largely depends on biomass, such as wood, animal dung and agricultural waste for domestic fuel sources that are typically burned in traditional stoves. Ethiopia has different biomass resource for biochar production, through pyrolysis cook stove co-producing biochar. Coffee husks are the major solid residues from the handling and processing of coffee in the study area. This study was to evaluate the biochar co-producing pyrolysis cook stove with respect to heat transfer through the bed and biochar yield. From allothermal type of pyrolysis cook stove, the stove design was selected for both the computational fluid dynamic （CFD） simulation and experimental measurements. ANSYS 14.5 was used for CFD simulation of the wood combustion. The production of biochar from coffee husk, corncob and sawdust at different heating times, bed and stove surface temperature were undertaken. Bulk density, pH and surface area of the biochar were measured. While good agreement between simulation and experimental result was obtained in the conduction phase during pyrolysis, deviation between the two on account of the effect of volatile gas in changing the temperature trend within the biomass bed was noticed. Within the biomass type, the maximum mean biochar yield （38.91%） was seen from coffee husk. In the case of different stove designs, the minimum mean biochar yield （27.11%） was found from normal Anila stove. The pH of biochar is found to be significantly affected by the type of biomass （9.83 mean for corncob and coffee husk, 6.43 mean for sawdust）, heating time （9.19 mean for 90 min and 8.01 mean for 30 min） and stove type （9.52 mean for normal Anila and 8.01 mean for flangeless Anila continuous feeding type）. In fact, the type of biomass is observed to significantly affect the bulk density and surface area ofbiochar.

Biochar for Soil Management： Effect on Soil Available N and Soil Water Storage

Soil management technologies for climate change adaptation and mitigation are needed to increase and sustain food production in smallholder agriculture while sequestering inert carbon in the soil. In a field studies at Crops Research Institute, Kwadaso-Kumasi Ghana, a control treatment, five inorganic fertilizer combinations （P30K60, N60P30K60, N120P30K60, NlsoP30K60 and N24oP3oK6o） and four biochar rates ＋ inorganic fertilizer （2 t/ha Biochar ＋ N60P30K60, 4 t/ha Biochar ＋ N60P30K60, 6 t/ha Biochar ＋ N6oP3oK6o and 8 t/ha Biochar ＋N6oP3oK6o） were assessed for their effect on soil moisture storage, soil available nitrogen and crop yield. The test crop was okra. Biochar amendments increased soil moisture storage by 14% relative to sole inorganic fertilizer applications. Biochar ＋ inorganic fertilizer relative to sole inorganic fertilizer increased soil available nitrate concentration by 85% at 0-15 cm soil depth but decreased soil ammonium-N by 71%. Compared to control, inorganic fertilizer （P3oK6o） resulted in more than 100% increase in okra fresh fruit yield. Addition of 60 kg N/ha to P3oK6o caused 23% decline in okra fresh fruit yield but showed 60% more okra fresh fruit yield than the control. Inorganic N rates of 120,180 kg N/ha and 240 kg N/ha combined with P3oK6o however caused a decline of 74% in okra fresh fruit yield. Biochar ＋ inorganic fertilizer increased okra fresh fruit yield by 100% compared to sole inorganic fertilizer. Biochar, an inert carbon, combined with inorganic fertilizer has tremendous potential to address food insecurity through soil moisture storage and soil N availability.

Switchgrass Biochar Effects on Plant Biomass and Microbial Dynamics in Two Soils from Different Regions

Biochar amendments to soils may alter soil function and fertility in various ways, including through induced changes in the microbial community. We assessed microbial activity and community composition of two distinct clayey soil types, an Aridisol from Colorado （CO） in the U.S. Central Great Plains, and an Alfisol from Virginia （VA） in the southeastern USA following the application of switchgrass （Panicum virgatum） biochar. The switchgrass biochar was applied at four levels, 0%,0, 2.5%, 5%, and 10%, approximately equivalent to biochar additions of 0, 25, 50, and 100 t ha^-1, respectively, to the soils grown with wheat （Triticum aestivum） in an eight-week growth chamber experiment. We measured wheat shoot biomass and nitrogen （N） content and soil nutrient availability and N mineralization rates, and characterized the microbial fatty acid methyl ester （FAME） profiles of the soils. Net N mineralization rates decreased in both soils in proportion to an increase in biochar levels, but the effect was more marked in the VA soil, where net N mineralization decreased from -2.1 to -38.4 mg kg^-1. The 10% biochar addition increased soil pH, electrical conductivity, Mehlich- and bicarbonate-extractable phosphorus （P）, and extractable potassium （K） in both soil types. The wheat shoot biomass decreased from 17.7 to 9.1 g with incremental additions of biochar in the CO soil, but no difference was noted in plants grown in the VA soil. The FAME recovery assay indicated that the switchgrass biochar addition could introduce artifacts in analysis, so the results needed to be interpreted with caution. Non-corrected total FAME concentrations indicated a decline by 457o and 34% with 10% biochar addition in the CO and VA soils, respectively, though these differences became nonsignificant when the extraction efficiency correction factor was applied. A significant decline in the fungi：bacteria ratio was still evident upon correction in the CO soil with biochar. Switchgrass biochar had the potential to cause short-term negative impacts on plant biomass and alter soil microbial community structure unless measures were taken to add supplemental N and labile carbon （C）.

Effects of Enriched Biochars Containing Magnetic Iron Nanoparticles on Mycorrhizal Colonisation,Plant Growth,Nutrient Uptake and Soil Quality Improvement

At present, there is little commercial sale of biochar, since farmers find they can not gain a return on their investment in this amendment in the first few years after its application, because of the high cost associated with large application rates. To overcome this constraint, development of artificially aged enriched biochar-mineral complexes(BMCs), having a higher mineral content, surface functionality, exchangeable cations, high concentration of magnetic iron(Fe) nanoparticles, and higher water-extractable organic compounds has been undertaken by a combined team of researchers and a commercial company. Two biochars produced under different pyrolysis conditions were activated with a phosphoric acid treatment. A mixture of clay, chicken litter, and minerals were added to the biochar, and then this composite was torrefied at either 180 or 220?C. In this study a pot experiment was carried out in glasshouse conditions to determine the effects of four different BMCs, with different formulations applied at rates of 100 and 200 kg ha-1, on the mycorrhizal colonisation, wheat growth and nutrient uptake, and soil quality improvement. It was found that the phosphorus(P) and nitrogen uptake in wheat shoots were significantly greater for a low application rate of BMCs(100 kg ha-1). The present formulation of BMC was effective in enhancing growth of wheat at low application rate(100 kg ha-1). The increase in growth appeared due to an increase in P uptake in the plants that could be partly attributed to an increase in mycorrhizal colonisation and partly due to the properties of the BMC.

Conocarpus Biochar Induces Changes in Soil Nutrient Availability and Tomato Growth Under Saline Irrigation

Thermally modified organic materials commonly known as biochar have gained popularity of being used as a soil amendment.Little information, however, is available on the role of biochar in alleviating the negative impacts of saline water on soil productivity and plant growth. This study, therefore, was conducted to investigate the effects of Conocarpus biochar(BC) and organic farm residues(FR) at different application rates of 0.0%(control), 4.0% and 8.0%(weight/weight) on yield and quality of tomatoes grown on a sandy soil under drip irrigation with saline or non-saline water. The availability of P, K, Fe, Mn, Zn and Cu to plants was also investigated. The results demonstrated clearly that addition of BC or FR increased the vegetative growth, yield and quality parameters in all irrigation treatments. It was found that salt stress adversely affected soil productivity, as indicated by the lower vegetative growth and yield components of tomato plants. However, this suppressing effect on the vegetative growth and yield tended to decline with application of FR or BC, especially at the high application rate and in the presence of biochar. Under saline irrigation system, for instance, the total tomato yield increased over the control by 14.0%–43.3% with BC and by 3.9%–35.6% with FR. These could be attributed to enhancement effects of FR or BC on soil properties, as indicated by increases in soil organic matter content and nutrient availability. Therefore, biochar may be effectively used as a soil amendment for enhancing the productivity of salt-affected sandy soils under arid conditions.

Effects of Different Biochars on Pinus elliottii Growth,N Use Efficiency,Soil N_2O and CH_4 Emissions and C Storage in a Subtropical Area of China

Intensive management of planted forests may result in soil degradation and decline in timber yield with successive rotations. Biochars may be beneficial for plant production, nutrient uptake and greenhouse gas mitigation. Biochar properties vary widely and are known to be highly dependent on feedstocks, but their effects on planted forest ecosystem are elusive. This study investigated the effects of chicken manure biochar, sawdust biochar and their feedstocks on 2-year-old Pinus elliottii growth, fertilizer N use efficiency （NUE）, soil N20 and CH4 emissions, and C storage in an acidic forest soil in a subtropical area of China for one year. The soil was mixed with materials in a total of 8 treatments： non-amended control （CK）; sawdust at 2.16 kg m^-2 （SD）; chicken manure at 1.26 kg m^-2 （CM）; sawdust biochar at 2.4 kg m^-2 （SDB）; chicken manure biochar at 2.4 kg m^-2 （CMB）; 15N-fertilizer alone （10.23 atom% 15N） （NF）; sawdust biochar at 2.4 kg m^-2 plus lSN-fertilizer （SDBN） and chicken manure biochar at 2.4 kg m^-2 plus 15N-fertilizer （CMBN）. Results showed that the CMB treatment increased P. elliottii net primary production （aboveground biomass plus litterfall） and annual net C fixation （ANCF） by about 180% and 157%, respectively, while the the SDB treatment had little effect on P. eUiottii growth. The 15N stable isotope labelling technique revealed that fertilizer NUE was 22.7% in CK, 25.5% in the NF treatment, and 37.0% in the CMB treatment. Chicken manure biochar significantly increased soil pH, total N, total P, total K, available P and available K. Only 2% of the N in chicken manure biochar was available to the tree. The soil N20 emission and CH4 uptake showed no significant differences among the treatments. The apparent C losses from the SD and CM treatments were 35% and 61%, respectively; while those from the CMB and SDB treatments were negligible. These demonstrated that it is crucial to consider biochar properties while evaluating their effects on plant growth and C sequestration.

Comparative Assessment of the Effect of Wastewater Sludge Biochar on Growth,Yield and Metal Bioaccumulation of Cherry Tomato

To investigate the potential effects of wastewater sludge and sludge biochar on growth, yield and metal bioaccumulation of cherry tomato （Lycopersicon esculentum L.）, a pot experiment was carried out under greenhouse environment with three different treatments, control soil （CP）, soil with wastewater sludge （SS） and soil with sludge biochar （SB）, to reveal the comparative effect between the amendments of wastewater sludge and sludge biochar. The soil used for pot experiment was Chromosol. Wastewater sludge and sludge biochax produced through pyrolysis process at 550 ℃ were applied at 10 t ha-1. No significant difference was found in growth and production of cherry tomatoes between wastewater sludge and sludge biochar applications to the soil. The accumulation rates of metals in the fruits were lower in the treatment with sludge biochar than in the treatment with wastewater sludge. The study highlights the benefits of risk mitigation from toxic metal accumulation in fruits using wastewater sludge and sludge biochar as soil conditioners.

Production of Biochar for Soil Application:A Comparative Study of Three Kiln Models

Biochar has potentials for soil fertility improvement, climate change mitigation and environmental reclamation, and charred biomass can be deliberately incorporated into soil for long-term carbon stabilization and soil amendment. Many different methods have been used for biochar production ranging from laboratory to industrial scales. However, in countryside of developing countries, biomass is generally used for cooking but not charred. Biochar production techniques at farmer scale have remained poorly developed. We developed and tested biochar production kilns for farmers with a dimension of 50.8 cm × 38.1 cm （height × diameter）, using three different setups for optimizing oxygen （02） limitation and syngas circulation： airtight with no syngas circulation （Model I）, semi-airtight with external syngas circulation （Model II） and semi-airtight with internal syngas circulation （Model III）. A comparative assessment of these biochar production kiln models was made considering biochar pyrolysis time, fuel to biomass ratio, biochar to feedstock ratio and thermogravimetric index （TGI）. Among the models, the best quality biochar （TGI ---- 0.15） was obtained from Model I kiln taking the longest time for pyrolysis （12.5 h） and the highest amount of fuel wood （1.22 kg kg-1 biomass）. Model III kiln produced comparatively good quality biochar （TGI = 0.11）, but with less fuel wood requirement （0.33 kg kg-1 biomass） and shorter pyrolysis time （8.5 h）. We also tested Model III kiln in a three times larger size under two situations （steel kiln and pit kiln）. The biochar to feedstock ratio （0.38） and quality （TGI =0.14） increased slightly for the larger kilns. Quality of biochar was found to be mainly related to pyrolysis time. The costs for the biochar stove and pit kiln were US$ 65-77, while it was US$ 154 for the large size steel kiln. Model III kiln can potentially be used for both cooking and biochar production at farmer scale.

Synergistic Effects of Biochar and NPK Fertilizer on Soybean Yield in an Alkaline Soil

Biochar effects on legume growth and biological nitrogen fixation have been studied extensively, mostly in acidic soils with laboratory produced biochar. In the present study, a pot experiment in a full factorial experimental design was performed to examine soybean yield and nodulation of three genotypes grown with or without biochar and NPK fertilizers in an alkaline soil. We observed synergistic effects of biochar and NPK fertilizer applications on biomass and seed yields for all three soybean genotypes. Total biomass production and seed yield increased on average by 67% and 54%, respectively, with biochar and by 201% and 182% with NPK fertilizer application compared to the control. When applications of biochar and NPK fertilizer were combined, the increases were 391% and367%, respectively. However, the biomass production in the control was very low(692 kg ha-1) due to a high soil p H(8.80). The nodulation increased with biochar and NPK fertilizer applications, and was largest with the combined application. A correlation was found between leaf chlorophyll content(single photon avalanche diode value) and nodule number. We suggested that the synergistic increase in yield was due to a decrease in soil p H caused by biochar and NPK fertilizer applications thereby increasing P availability in this alkaline soil.

Effects of Biochars and Other Organic Soil Amendments on Plant Nutrient Availability in an Ustoxic Quartzipsamment

A sandy soil, Nampong soil （classified as Ustoxic Quartzipsamment）, was incubated under controlled condition i） to compare the mineralization of major plant nutrients derived from different types of biochars and other organic soil amendments; ii） to examine their effects on soil properties and plant nutrient availability; and iii） to evaluate the plant nutrient losses in leachate from the rooting zone of soil incorporated with the different amendments. The experiment was arranged in a completely randomized design with 3 replications. Five treatments of soil amendments used were cassava stem base biochar （CSB）, rice husk biochar （RHB）, chicken manure （CM）, compost （CP）, and no amendment application （control）. The RHB treatment released the highest amounts of mineralized NO^-N, available P and K （2.30-17.26, 5.50-42.90 and 43.00-187.63 mg kg-1, respectively） while the CM treatment releasing the highest NH4＋-N in the range of 1.86-53.67 mg kg-1. The CSB and RHB treatments showed better continuity of mineralization of nutrients than the treatments of CM and CP, particularly in the case of the CSB treatment. In the soil column incubation experiment, the amounts of NH4＋-N and NO3-N in all treatments barely changed on Day 1 to Day 30 of incubation and then the amounts increased markedly on Day 60. On Day 601 the RHB treatment contained a very high amount of NO3--N （〉 250 mg kg-1）. This suggests that N would become more available 30 d after the incorporation. The CM treatment gave the highest amounts of organic matter and available P in the ranges of 4.64-8.94 g kg-1 and 14.41-36.33 mg kg-1, respectively, during the 60-d column incubation. The CSB treatment tended to have higher available K throughout the measuring period. The NO3--N was leached from the soil column quite quickly on Day 1 of incubation while the loss of NH^-N decreased slightly from Day 1 until the end of the measurement. The amounts of P and K losses varied with the type of soil amendments, and the pattern of the loss was irregular.

Biomass and Energy of Casuarina equisetiofolia Plantations in Southeast Coast of China

The biomass and energy production of Casuarina equisetifolia plantations aged 14 were studied in Huian County, Fujian Province, Southeast of China. The standing crop biomass was 152.60 t/ha, in which the biomass of bole was 67.02 t/ha, accounting for 43.94 % of the total, while that of root was 36.83 t/ha and 24.14 %, respectively. Net primary productivity was 10.17t/(ha.a).The range of gross caloric of components was 19.29～20.23 kJ/g, with the average 19.70 kJ/g. The standing crop energy was 2 987×10^6 kJ/ha. Net energy production was 196.8×10^6 kJ/ha, while solar energy conversion efficiency was 0.90%.