生物质炭添加对华南双季稻田碳排放强度的影响

中国农田有机物料资源化利用是一项巨大挑战。为研究生物质炭农田施用的生态效应,探讨华南双季稻田碳排放强度(greenhouse gas intensity,GHGI)对生物质炭添加的响应,开展了基于静态箱-气相色谱法的连续两年野外观测。田间试验共设6个处理,即当地农民习惯(CK,化肥,无稻草还田),3个不同用量生物质炭添加处理,即BC1(5 t/hm2)、BC2(10 t/hm2)和BC3(20 t/hm2),和2个稻草还田处理(直接还田和稻草+腐熟剂还田)。结果表明,相比当地农民习惯和稻草还田处理生物质炭添加有效抑制了双季稻田温室气体排放(平均降低温室气体排放当量49.87%),显著降低了土壤容重,增强作物的碳氮养分吸收能力,稳定了水稻产量(平均增产3.54%),降低了稻田碳排放强度(平均降低52.13%)。4个生长季平均而言,相比CK、RS和RI,生物质炭3个处理分别降低稻田100a尺度上温室气体排放当量27.53%,58.65%和63.43%(P0.05),分别增产3.21%,5.11%和2.29%(P0.05),进而分别降低100a尺度上GHGI 30.57%,61.00%和64.82%(P0.05),综合而言,BC3具有较好的减排增产潜力。相关矩阵和主成分分析可视化表达了在生物炭添加影响下,稻田碳排放强度与水稻生长参数及土壤理化特性的关系。生物质炭添加影响着水稻产量、收获指数、土壤有机质、总碳和植株吸氮量等环境变量的分布。通过多元决策回归树分析,发现可通过水稻收获指数(0.5)定量判别其碳排放强度。该研究结果表明,通过优化田间管理,适量生物质炭回田(20 t/hm2)利用是增强土壤固碳、稳定水稻产量、降低稻田碳排放强度和应对气候变化不利影响的可行途径。该研究可为中国秸秆资源科学利用提供基础研究案例。     

生物炭的10年土壤培肥效应

大量短期的室内试验和田间试验研究表明,施用生物炭可以增加土壤碳固定,提升土壤肥力和作物产量,然而关于生物炭的长期土壤肥力效应尚不明确。为此,依托持续10年的生物炭的田间定位试验[4个处理:对照(CK)、生物炭4. 5 t·hm-2·年-1(B4. 5)、生物炭9 t·hm-2·年-1(B9. 0)、秸秆还田(SR)],研究了长期施用生物炭对土壤肥力状况的影响。结果显示,与对照相比,长期施用生物炭和秸秆还田对土壤p H值没有显著影响,但容重降低了2. 2%～8. 2%,施用生物炭的土壤电导率降低了1. 5%～7. 8%,而秸秆还田处理土壤电导率提高了4. 7%～13. 4%。施炭和秸秆还田使土壤有机质(SOM)含量增加57. 7%～123. 1%,总氮含量提高11. 3%～21. 9%,总磷没有显著性变化。不同处理土壤NH+4-N含量的差异不显著,而施用生物炭和秸秆还田土壤NO-3-N含量增加3. 8%～67. 1%,且高炭处理的效果显著。土壤有效磷含量显著降低了23. 1%～42. 0%,速效钾含量上升了2. 0%～23. 1%。总体而言,长期施用生物炭提升了土壤肥力,尤其是对土壤有机质的提升有显著的效果。     

Effects of compost,biochar and manure on carbon mineralization of biogas residues applied to soil

Biogas residues contain microbial biomass, which contributes to the formation of soil organic matter. Whether the potential of biogas residues to increase soil organic matter can be enhanced by co‐application with compost, biochar or manure is unknown, however. The aim of this paper is to evaluate the effects of co‐amendment on the mineralization of biogas residues, carbon dioxide emissions and the carbon flow within the microbial food web. We determined the fate of ¹³C‐labelled microbial biomass present in biogas residues applied together with compost, biochar and manure to soil, by analysing CO₂ and biomarker phospholipid fatty acids. Although the rate of mineralization constant of the slowly degrading carbon pool was not affected by co‐amendments, co‐amendment with manure resulted in a larger rate of mineralization constant of the readily degrading carbon pool of biogas residues. The incorporation of carbon was mainly to Gram‐negative biomass and was the smallest with manure co‐amendment, which indicated differences in bioavailability of the carbon source.     

Initial and subsequent effects of hydrochar amendment on germination and nitrogen uptake of spring barley

The application of hydrochars as soil amendments could be an option to ameliorate soil quality by enhancing nutrient and water‐holding capacity of sandy soils. But when hydrochar application is directly followed by sowing, it can decrease the soil mineral‐N concentration and the germination rate of crops. We currently lack evidence, whether these effects are persistent or transient and thus can be avoided by adjusting the application strategy, e.g., by prolonging the period between application and sowing. A set of pot trials with spring barley (Hordeum vulgare L.) was performed to study the initial and subsequent effects of different hydrochar amendments on germination, biomass production, and plant N availability. To this end, two subsequent cultivations of barley were grown on hydrochar‐amended soil–peat substrates. The first barley cultivation was sown directly after hydrochar application. After the harvest, the same substrates were cultivated with barley again. Germination, biomass production, and N concentration in the biomass were reduced when sowing directly followed the application of hydrochars. Differences in germination rate and biomass production between hydrochar treatments depended on the hydrochar feedstock. A recultivation of the hydrochar‐amended substrates 9 weeks after hydrochar application showed no significant effects on germination and biomass production. The N concentration in plants was still lower in the hydrochar treatments despite additional fertilization. The N immobilized during the first cultivation period was not released in the following weeks. We conclude that the germination‐inhibiting substances in hydrochars were removed in the weeks after soil incorporation. This is probably due to microbial degradation of hydrochar components and a consecutive immobilization of mineral N. Hydrochar amendment had only short‐term effects on germination and biomass production of barley that can be avoided by applying hydrochar at least 4 weeks prior to sowing. The N concentration in plants was persistently low even 4 months after hydrochar application which can only be redeemed by adjusting the fertilization strategy.     

Hydrochar amendment promotes microbial immobilization of mineral nitrogen

Hydrochars and biochars are products of the carbonization of biomass in different conversion processes. Both are considered suitable soil amendments, though they differ greatly in chemical and physical composition (e.g., aromaticity, inner surface area) due to the different production processes (pyrolysis, hydrothermal carbonization), thus affecting their degradability in soil. Depending on the type, char application may provide soil microorganisms with more (hydrochars) or less (biochars) accessible C sources, thus resulting in the incorporation of nitrogen (N) into microbial biomass. A soil‐incubation experiment was conducted for 8 weeks to determine the relationship between mineral‐N concentration in the soil solution and microbial‐biomass development as well as soil respiration. An arable topsoil was amended with two hydrochars from feedstocks with different total N contents. Biochars from the same feedstocks were used for comparison. Both char amendments significantly decreased mineral‐N concentration and promoted microbial biomass compared to the nonamended control, but the effects were much stronger for hydrochar. Hydrochar application increased soil respiration significantly during the first week of incubation, simultaneous with the strongest decrease in mineral‐N concentration in the soil and an increase in microbial biomass. The amount of N detected in the microbial biomass in the hydrochar treatments accounted for the mineral N “lost” from the soil during incubation. This shows that microbial immobilization is the main sink for decreasing mineral‐N concentrations after hydrochar application. However, this does not apply to biochar, since the amount of N recovered in microorganisms was much lower than the decrease in soil mineral‐N concentration. Our results demonstrate that while both chars are suitable soil amendments, their properties need to be considered to match the application purpose (C sequestration, organic fertilizer).     

Soil organic and inorganic carbon sequestration by consecutive biochar application: Results from a decade field experiment

Biochar addition can expand soil organic carbon (SOC) stock and has potential ability in mitigating climate change. Also, some incubation experiments have shown that biochar can increase soil inorganic carbon (SIC) contents. However, there is no direct evidence for this from the field experiment. In order to make up the sparseness of available data resulting from the long‐term effect of biochar amendment on soil carbon fractions, here we detected the contents and stocks of the bulk SIC and SOC fractions based on a 10‐year field experiment of consecutive biochar application in Shandong Province, China. There are three biochar treatments as no‐biochar (control), and biochar application at 4.5 Mg ha^?1 year^?1 (B4.5) and 9.0 Mg ha^?1 year^?1 (B9.0), respectively. The results showed that biochar application significantly enhanced SIC content (3.2%–24.3%), >53 μm particulate organic carbon content (POC, 38.2%–166.2%) and total soil organic carbon content (15.8%–82.2%), compared with the no‐biochar control. However, <53 μm silt–clay‐associated organic carbon (SCOC) content was significantly decreased (14%–27%) under the B9.0 treatment. Our study provides the direct field evidence that SIC contributed to carbon sequestration after the biochar application, and indicates that the applied biochar was allocated mainly in POC fraction. Further, the decreased SCOC and increased microbial biomass carbon contents observed in field suggest that the biochar application might exert a positive priming effect on native soil organic carbon.     

生物质炭施用对马铃薯产量和品质的影响

通过田间试验,观测分析不同生物质炭用量(0、20和40 t/hm~2)下马铃薯产量、品质和土壤肥力的变化及其年际效应,为生物质炭在马铃薯生产过程中的应用提供理论依据。结果表明,低剂量生物质炭施用(20 t/hm~2)显著提高了马铃薯总产量和商品率,生物质炭施用后第一年马铃薯总产量比对照提高了41.08%。当生物质炭用量为40 t/hm~2时,马铃薯产量与对照没有显著差异但降低了一些品质指标,其中2016年干物质和淀粉含量比对照降低了18.47%和24.03%。生物质炭施用显著提高了土壤有机碳、有效磷和速效钾含量,并增加了土壤C/N和电导率;而对土壤p H和全氮含量的影响与生物质炭施用年限有关。生物质炭施用量和施用年限显著影响马铃薯产量和品质。低剂量生物质炭施用能显著提高马铃薯产量,但第二年无增产效果;随着生物质炭用量增加马铃薯增产效果消失,还可能会降低马铃薯品质。生物质炭施用后马铃薯产量变化与土壤紧实度改善无必然联系。     

Effects of biochar amendment on greenhouse gas emissions,net ecosystem carbon budget and properties of an acidic soil under intensive vegetable production

Biochar addition to soils has been frequently proposed as a means to increase soil fertility and carbon (C) sequestration. However, the effect of biochar addition on greenhouse gas emissions from intensively managed soils under vegetable production at the field scale is poorly understood. The effects of wheat straw biochar amendment with mineral fertilizer or an enhanced‐efficiency fertilizer (mixture of urea and nitrapyrin) on N₂O efflux and the net ecosystem C budget were investigated for an acidic soil in southeast China over a 1‐yr period. Biochar addition did not affect the annual N₂O emissions (26–28 kg N/ha), but reduced seasonal N₂O emissions during the cold period. Biochar increased soil organic C and CO₂ efflux on average by 61 and 19%, respectively. Biochar addition greatly increased C gain in the acidic soil (average 11.1 Mg C/ha) compared with treatments without biochar addition (average ?2.2 Mg C/ha). Biochar amendment did not increase yield‐scaled N₂O emissions after application of mineral fertilizer, but it decreased yield‐scaled N₂O by 15% after nitrapyrin addition. Our results suggest that biochar amendment of acidic soil under intensive vegetable cultivation contributes to soil C sequestration, but has only small effects on both plant growth and greenhouse gas emissions.     

Does soil amended with biochar and hydrochar reduce ammonia emissions following the application of pig slurry?

Combining amendments to the soil made by biochar or hydrochar with nitrogen (N) fertilizer can modify soil N dynamics and availability. Such a response suggests that these amendments would affect ammonia (NH₃) emissions from slurry similarly, and potentially reduce volatilization of NH₃. This study measured the potential emissions of NH₃ following application of pig slurry to the surface of silt‐loam and loam soils amended with biochar and hydrochar (both derived from Miscanthus × giganteus (Greef et Deu)) at a rate of 3% soil dry weight (16 t ha^?1 soil area, on average) and 60% water‐filled pore space (WFPS). The experiment was carried out in a dynamic chamber connected to a photo‐acoustic trace gas analyser in a controlled climate (20°C) for 48 hours. Statistically significant differences (P < 0.05) in total emissions were observed between both treatment and soil types. Surprisingly, both amendments increased emissions of NH₃ compared with the control; cumulative NH₃ emissions averaged 38.7 and 23.5% of applied total ammonium nitrogen (TAN) for hydrochar and biochar, respectively, whereas it was 18.2% for the control. The larger emissions in hydrochar‐amended soil were attributed to the reduced ability to absorb NH₄⁺ associated with greater hydrophobicity and strong pH buffering of the slurry. Furthermore, final soil analyses with deionised water extracts showed significant differences (P < 0.05) in mineral N concentration between treatments. The smaller ammonium concentrations in biochar‐amended soil suggest that some NH₄⁺‐N was immobilized by adsorption on to biochar surfaces. This study observed that biochar and hydrochar properties, as well as soil characteristics, play important roles in controlling NH₃ emissions from surface slurry applications. The results obtained identified circumstances where these amendments even enhance volatilization, which provides new information on and insight into the extent and limitations of the potential of biochar and hydrochar for the mitigation of emissions.     

城市园林废弃物生物质炭对小白菜生长、 硝酸盐含量及氮素利用率的影响

【目的】我国温室种植蔬菜迅速发展,温室种植中肥料利用率低及蔬菜硝酸盐积累等问题日益突出。同时,我国城市化快速发展,城市园林废弃物日益增多,这些木质废弃物的处理也成为城市可持续发展的挑战。本文采用城市园林废弃物制成的生物质炭用于温室栽培生产,分析其对温室蔬菜产量和品质以及养分保持的影响,从而探索一种为绿色环保的现代城市农业服务的技术。【方法】本研究采用温室盆栽试验方法,以小白菜为研究对象,设置5个生物质炭添加水平。 C0 (0 g/kg, CK)、 C1(20 g/kg)、 C2(40 g/kg)、 C3(60 g/kg)和C4(80 g/kg)。研究生物质炭对小白菜产量、 植株硝酸盐含量、 土壤氮素含量与形态以及氮素保持效应的影响。【结果】与对照相比,添加不同比例的生物质炭均显著提高小白菜产量,其中,C3和C4处理下增产幅度达到75%,生物质炭添加量与产量呈显著正相关关系;生物质炭对小白菜植株地上部和地下部的影响并不一致,其中收获指数显著增加,提高幅度在2.5%～9.5%之间,有随着生物质炭用量增加而增加的趋势;对照处理小白菜地上部硝酸盐含量达504 mg/kg,各处理植株硝酸盐含量介于161～256 mg/kg之间,显著降低50%以上,特别是C1处理降低硝酸盐含量的幅度达到68%,而不同生物质炭添加量之间植株硝酸盐含量差异不显著;生物质炭的添加增加了土壤中总氮素的含量,氮素损失率由不施炭处理的5.6%降低到了3.3%以下,显著降低了42%,同时土壤氮素生产率较对照提高幅度大于35%;与C0相比较,生物质炭添加显著降低了土壤NO-3-N的积累,降低幅度在60%以上,生物质炭用量在4%左右时降低作用最大,达到80%,同时土壤NH+4-N在生物质炭添加下降低了77%,生物质炭对降低土壤中铵态氮和硝态氮的累积作用并不与其用量呈正相关,铵硝比随着生物质炭添加量而呈下降的趋势;同时从研究结果看,产量与土壤NH+4-N和NO-3-N含量呈负相关关系,与土壤全氮呈正相关关系,而蔬菜植株硝酸盐含量与土壤NH+4-N和NO-3-N含量具有相关性,但与土壤全氮含量相关性不显著。【结论】温室大棚栽培小白菜的土壤中, 加入不同量的生物质炭能显著提高小白菜产量,同时降低小白菜植株的硝酸盐含量,添加量在2%时效果最好;土壤硝态氮和铵态氮积累随生物质炭施入而降低;生物质炭显著降低氮素损失率而提高氮素生产率。本研究得出生物质炭通过降低损失、 吸持更多氮素而提高了氮素的持续供应,在增产的同时降低了蔬菜硝酸盐积累,提高了品质。因此,在温室大棚蔬菜生产的土壤中添加一定量生物质炭(本试验下添加2%～4%)可以达到高产和优质。     

Impact of pyrochar and hydrochar on soybean (Glycine max L.) root nodulation and biological nitrogen fixation

The aim of this study was to identify effects of carbonized organic material (“biochar”) on soybean growth, root nodulation and biological nitrogen fixation, and to elucidate possible underlying mechanisms. Soybean (Glycine max L.) was grown in four arable soils amended with carbonized organic material produced from wood or maize as feedstocks, by pyrolysis (“pyrochar”) or hydrothermal carbonization (“hydrochar”). Nodulation by Bradyrhizobium , biological nitrogen fixation (BNF) assessed by ¹⁵N techniques, plant growth, nutrient uptake and changes in chemical soil properties after soil amendment were determined. Data were analyzed by means of a three way ANOVA on the factors soil, carbonization technique and feedstock. It turned out that soybean root nodulation and BNF was influenced by the carbonization technique used to prepare the soil amendment. Hydrochar, in average and across all soils, increased nodule dry matter and BNF by factors of 3.4 and 2.3, respectively, considerably more than pyrochar, which led to 1.8 and 1.2 fold increases, respectively. Nodule dry matter and BNF correlated positively with available soil sulfur and negatively with available soil nitrogen. Hydrochars provided more available sulfur than pyrochars, and hydrochars caused a decrease in nitrogen availability in the soil solution, thereby exerting a positive influence on nodulation and BNF. Pyrochar amendment increased soil pH but had no effect on nodulation and BNF. Plant growth was affected by the soil and by the feedstock used for the “biochar”, and increased slightly more in treatments with pyrochar and hydrochar made from maize, which was richer in nitrogen and potassium. The results show that carbonized organic materials, and specifically hydrochar, have the capacity to increase BNF in soils. We suggest that this enhancement in BNF in response to soil amendments with carbonized organic materials is due to an increase in available sulfur and a reduction of available soil nitrogen.     

Maize straw is more effective than maize straw biochar at improving soil N availability and gross N transformation rate

Soil nitrogen (N) transformation is vital in determining farmland N availability. Although many studies have investigated the effect of biochar on N retention and loss via leaching and gaseous emissions, few have determined the dynamics of gross N transformation during crop growth in long-term biochar-amended soils and compared the effect of the biochar with that of its feedstock. In this study, we conducted a five-time field measurement of soil gross N turnover rates via ¹⁵N isotope pool dilution during maize growth in 2021. Three treatments were employed, including no amendment, biochar and straw applied annually at rates of 2.63 and 7.50 t ha⁻¹, respectively, since 2013. The results showed that biochar did not change the rate of gross N mineralisation when compared with no amendment, but straw increased it by 139% in August, resulting in significantly higher cumulative gross N mineralisation than biochar and no amendment (701 vs 489 and 499 mg kg⁻¹ in 200 d). The inconsistent influence was attributed to the fact that inherent biochar-N was recalcitrant and could not be mineralized like the straw. The gross nitrification rate was decreased by 72.9% and 77.4% by biochar and straw application, respectively, in June relative to no amendment, but then it increased from July to August in the straw treatment as a result of the elevated gross N mineralisation rate. The decreased nitrification in the biochar treatment was an outcome of the synergetic effect of a low ammonium pool (−59.4%) and a high gross ammonium immobilisation rate (+263%), which was likely due to excessive fertilizer N loss and abiotic adsorption to biochar. Meanwhile, biochar amendment inhibited bacterial 16S and fungal ITS genes, as well as ureC and bacterial and archaea-amoA gene copies. In conclusion, straw is more effective than biochar at improving soil N transformation and availability in the long term.     

生物炭与氮肥对稻田甲烷氧化菌和产甲烷菌数量和潜在活性的影响

基于稻田中氮肥配施生物炭的田间定位试验,研究了施用生物炭与氮肥对旱季稻田土壤理化性质、甲烷氧化与产生潜势及甲烷氧化菌和产甲烷菌丰度的影响。田间试验共设置5个处理：单施生物炭、单施氮肥、氮肥配施生物炭（生物炭设置两个水平）以及对照。结果表明：施用生物炭三年后显著提高了有机碳和微生物生物量碳含量（p﹤0.05）,与单施氮肥处理相比,氮肥配施生物炭后可显著提高土壤pH。与对照相比,单施生物炭显著提高土壤甲烷氧化潜势。在施氮条件下,甲烷氧化潜势与生物炭施用量之间存在正相关关系,与氮肥配施20 t hm-2处理相比,40 t hm-2生物炭处理甲烷氧化潜势增长53.8%。氮肥配施高倍生物炭与配施低倍生物炭处理相比产甲烷潜势由0.001提高至0.002 mg kg-1 h-1;氮肥施用一定程度上抑制了甲烷氧化菌数量的增长,单施氮肥处理中产甲烷菌数量较对照处理显著增加了3.0%;单施或配施低水平生物炭显著增加土壤甲烷氧化菌数量。氮肥显著降低了甲烷氧化菌与产甲烷菌基因丰度比（pmoA/mcrA）。而在同氮肥水平下施加生物炭显著增加了土壤pmoA/mcrA比值,即生物炭对甲烷氧化菌的促进作用显著高于产甲烷菌,提高了旱季稻田土壤的甲烷氧化能力,因此有助于减少稻田土壤甲烷的排放。     

Effect of labile and recalcitrant carbon on heterotrophic nitrification in a subtropical forest soil

Carbon (C) is an important factor controlling heterotrophic nitrification in soil, but the effect of individual C components (e.g., labile and recalcitrant C) is largely unclear. We carried out a C amendment experiment in which either labile C (glucose) or a recalcitrant C (cellulose and biochar) was added to a subtropical forest soil. A ¹⁵N-, ¹³C-tracing and MiSeq sequencing study was performed to investigate soil gross heterotrophic nitrification rates, carbon utilization for soil respiration and microbial biomass production and microbial composition, respectively. After 2 days, results showed a significant increase of gross heterotrophic nitrification rate in glucose (GLU) (on average 3.34 mg N kg⁻¹ day⁻¹), cellulose (CEL) (on average 0.21 mg N kg⁻¹ day⁻¹) and biochar (BIO) (on average 0.13 mg N kg⁻¹ day⁻¹) amendment in comparison with the unamended soil (CK) (on average 0.01 mg N kg⁻¹ day⁻¹; p < 0.05). The contribution of heterotrophic nitrification to total soil nitrification was significantly larger in GLU (average 85.86%), CEL (average 98.52%) and BIO (average 81.25%) treatments compared with CK (average 33.33%; p < 0.01). After 2-month amendment, the gross rates remarkably decreased in GLU (average 0.02 mg N kg⁻¹ day⁻¹), and the contribution to total nitrification (average 8.73%) were significantly lower than that in CK (p < 0.05). A decrease in the proportion of heterotrophic nitrification to total nitrification in soil was also observed in CEL (average 38.40%) and BIO (6.74%) treatments. Nevertheless, BIO amendment (compared to CK, GLU and CEL) showed the highest gross heterotrophic nitrification rate, accompanied by a notably higher abundance of specific heterotrophic nitrifiers, i.e. Trichoderma, Aspergillus and Penicillium. These results point to a stimulatory effect of C addition on soil heterotrophic nitrification in the short term, while the stimulatory impact of C amendment diminishes with the decline in easily available C. In addition, a shift of the microbial composition in the long term can possibly be sustained for longer if additional recalcitrant C is available to heterotrophic nitrifiers. The dynamic response of heterotrophic nitrification to labile and recalcitrant C in this study offered an explanation for the positive effect of plantation and plant root exudation on the process.     

生物质炭和秸秆长期还田对红壤团聚体和有机碳的影响

要 ：秸秆还田和施用生物炭是提高土壤有机碳含量和改良土壤团聚体结构的有效方法,但长期施用生物炭与秸秆还田改良土壤的效率研究仍然缺乏比较。本研究针对中亚热带典型的旱地红壤,基于等碳量不同碳源投入的5年野外定位试验,研究秸秆还田、秸秆-猪粪配施和生物炭还田对红壤团聚体组成、稳定性和有机碳分布的影响,为建立红壤地力快速提升的有机培肥措施提供科学依据。本试验共设置对照、单施化肥、秸秆还田、秸秆-猪粪配施和生物炭还田五个处理,采用干筛和湿筛法分析了连续施用不同碳源5年后对土壤团聚体组成、稳定性和有机碳分布的影响。研究表明,施用等碳量的不同有机碳源5年后显著增加了土壤有机碳含量,其增幅顺序为：生物炭还田>秸秆-猪粪配施>秸秆还田。干筛法分析结果表明：与单施化肥处理相比,秸秆-猪粪配施和生物炭还田处理显著增加>0.25 mm机械稳定性团聚体含量(R_0.25)、平均重量直径(mean weight diameter, MWD)和几何平均直径(geometric mean diameter, GMD);秸秆还田和生物炭还田处理显著增加了0.25-2 mm团聚体对土壤有机碳的贡献率。湿筛法分析结果表明：与单施化肥处理相比,秸秆还田和秸秆-猪粪配施处理显著增加R_0.25、MWD和GMD,但生物炭还田处理和单施化肥处理相比差异不显著;秸秆还田和秸秆-猪粪配施处理显著降低团聚体破坏率(PAD),生物炭还田处理显著增加了PAD;秸秆配施猪粪处理和秸秆还田处理显著增加了>2mm团聚体对土壤有机碳的贡献率。总体上,秸秆配施猪粪协同提高团聚体有机质含量和团聚体稳定性的作用比秸秆还田和生物炭还田要强。     

杉木凋落物及其生物炭对土壤微生物群落结构的影响

以福建建瓯万木林自然保护区内的杉木人工林土壤为研究对象,设置单独添加生物炭、单独添加凋落物以及混合添加凋落物和生物炭处理,进行一年的室内培养实验,研究不同添加物处理对土壤性质及微生物群落结构的影响。结果表明:与对照(S)相比,单独添加凋落物与混合添加凋落物和生物炭均使土壤磷脂脂肪酸(PLFA)总量、真菌丰度以及真菌/细菌比值显著增加;单独添加生物炭与混合添加凋落物和生物炭均使革兰氏阳性细菌/革兰氏阴性细菌比值显著增加。混合添加凋落物和生物炭处理的放线菌丰度显著高于单独添加凋落物处理的。主成分分析表明,不同添加物处理的土壤微生物群落结构存在显著差异;典范对应分析表明,不同添加物处理通过改变土壤p H、全碳、全氮、C/N、可溶性有机碳(DOC)和可溶性有机氮(DON)等性质,进而影响土壤微生物群落结构。     

Long‐term effect of compost and inorganic fertilizer on activities of carbon‐cycle enzymes in aggregates of an intensively cultivated sandy loam

The activities of carbon‐cycle enzymes were measured in soil and aggregates to understand compost and inorganic fertilizer amendment effects on soil organic carbon accumulation in an intensively cultivated upland field. Soil samples were collected from a long‐term field experiment with seven treatments: compost, half‐compost N plus half‐fertilizer N, fertilizer NPK, fertilizer NP, fertilizer NK, fertilizer PK and no fertilizer control. The 18‐yr continuous application of compost increased organic C content in soil and three aggregate sizes by 72–124 and 78–234%, respectively, compared with the control. Fertilization also significantly increased organic C contents in soil, macroaggregates and the silt + clay fraction, but not in microaggregates. Compost application significantly reduced the specific activities of polyphenol oxidase (activity per unit organic C) in soil and three aggregate sizes compared with control, whereas fertilization had a much weaker effect. Compost amendment also significantly lowered the specific activities of invertase in macroaggregates and the silt + clay fraction, and this effect was more pronounced than the addition of fertilizer NPK. In contrast, inorganic fertilizer and compost application significantly increased the specific activities of cellobiohydrolase in soil, macroaggregates and microaggregates (but not in the silt + clay fraction), and xylosidase in microaggregates. The application of fertilizer NPK had a more pronounced effect than compost. We considered that the increase in organic C in compost‐amended soil was therefore probably associated with the accumulation of lignocellulose and sucrose in macroaggregates, lignocellulose and hemicellulose in microaggregates and lignin (its derivative) and nonstructural carbohydrates in the silt + clay fraction. However, the application of fertilizer NPK enhanced organic C probably due to an increase in the content of lignin (its derivative) and sucrose in macroaggregates and the silt + clay fraction. Therefore, the application of compost with high lignocellulose should be effective to increase soil organic C in the North China Plain.     

Impacts of straw biochar additions on agricultural soil quality and greenhouse gas fluxes in karst area,Southwest China

Understanding and improving environmental quality by reducing soil nutrient leaching losses, sequestering carbon (C), reducing greenhouse gas (GHG) emissions, and enhancing crop productivity in highly weathered or degraded soils have always been the goals of agroecosystem researchers and producers. Biochar production and soil incorporation strategies have been recently proposed to help attain these goals. However, the effect of such approaches on soil GHG fluxes is highly uncertain and needs to be further assessed before biochar can be used on a large scale. In addition, the duration of these GHG reductions is not known and is of pivotal importance for the inclusion of biochar in climate abatement strategies. In a field trial cultivated with Chinese cabbage (Brassica campestris ssp. pekinensis) and radish (Daucus carota L. var. Sativa Hoffm), rapeseed (Brassica campestris L.) and maize (Zea mays L.) straw-derived biochar was added to the soil at rates of 0, 26, 64 and 128 t ha^?1, in the whole growing season (October 2011–March 2012) to monitor the effect of treatments on soil GHG production/consumption and soil quality 16 months after biochar addition. The results showed that biochar amendment increased soil pH, nitrate nitrogen content, available phosphorus content and soil water content, but decreased soil bulk density. In biochar-treated plots, soil carbon dioxide (CO₂) fluxes were from 20.1 to 87.0% higher than in the control. Soil methane (CH₄) uptakes were increased significantly, by 33.2 and 80.1%, between the biochar amendment at the rate of 64 and 128 t ha^?1 and the control. Soil nitrous oxide (N₂O) fluxes showed no significant difference between biochar amendment and the control. Overall only the CH₄ uptake-promoting effect continued into the long term, 16 months after biochar incorporation. This study demonstrates that the beneficial effects of biochar addition might first come through soil quality improvement and carbon sequestration, rather than through effects on the repression of soil C mineralization or the nitrogen cycle.     

长期不同量秸秆炭化还田下水稻土孔隙结构特征

  【目的】  生物炭被认为是一种能够提高土壤固碳能力、改善土壤结构和减缓全球气候变化的土壤改良剂。土壤孔隙结构直接影响土壤中水、气、热的运动,因此,研究长期施用生物炭对土壤孔隙结构特征的影响,以期为秸秆炭化还田提供理论依据。  【方法】  研究基于2013年建立的水稻秸秆炭化还田长期定位试验,选取在等氮磷钾条件下不施用生物炭 (C0)、施用低量生物炭 (1.5 t/hm2,C1.5)、高量生物炭 (3.0 t/hm2,C3.0)的 3个处理。利用X射线CT扫描和图像处理技术,分析了土壤孔隙结构参数,包括土壤孔隙度、土壤孔隙大小分布、孔隙连通性指数 (欧拉特征值)、各向异性、分形维数、最紧实层孔隙度和最紧实层平均孔隙直径等参数。  【结果】  C1.5和C3.0处理均能显著增加土壤有机碳含量和土壤总孔隙度,降低土壤容重,平均增加或降低比例分别为15.5%、10.5%和7.4%。C1.5与C3.0处理之间的总孔隙度没有显著差异,但孔隙大小分布存在差异。C1.5处理显著增加了大孔隙中当量孔径为100～500 μm和 > 500 μm的孔隙度,增幅分别为81.6%和275.3%,而C3.0处理显著降低了大孔隙中当量孔径100～500 μm的孔隙度,降幅为32.9%。C3.0处理当量孔径 < 25 μm的孔隙度显著大于C0处理和C1.5处理,增幅分别为13.8%和16.3%。C1.5处理的欧拉特征值最低,分形维数、最紧实层孔隙度和平均孔隙直径最大。各处理土壤孔隙的各向异性没有显著差异。  【结论】  长期施用水稻秸秆生物炭能够显著增加稻田土壤有机碳含量和总孔隙度,降低土壤容重。施用适量生物炭会增加土壤大孔隙度和土壤孔隙的连通性,但是过量施用生物炭可能会降低土壤大孔隙度和土壤孔隙的通气导水能力。炭化秸秆还田量与孔隙结构之间的定量关系还需深入研究。     

Effects of hydrochar application on the dynamics of soluble nitrogen in soils and on plant availability

Before hydrochars can be applied as soil amendments in agriculture, information about how hydrochar application affects soil nutrient cycles and plant growth are necessary. In this study, incubation experiments were performed to investigate hydrochar effects on N concentrations (NO$ _3^- $ , NH$ _4^+ $ ) in soils with different N pools (soil N, fertilizer N). A set of pot trials with three crop species (barley, phaseolus bean, leek) was conducted to determine hydrochar effects on plant N availability and biomass production after mineral‐N fertilization. Results of the incubation experiments show that hydrochar reduced the concentration of mineral N in soil within the first week after incorporation, especially that of nitrate. This was particularly evident, when hydrochars with high C : N ratio, high DOC and low mineral‐N contents were applied. Hydrochars promoted biomass production of barley and phaseolus bean in pot trials, which can be partly attributed to an increase in soil pH after hydrochar incorporation. Dry‐matter yield of leek tended to decrease after hydrochar application. Hydrochars with high C : N ratio decreased the plant's N content, an effect that was strongest with increased hydrochar concentration. Hydrochars with low C : N ratio did not affect the crop's N uptake. Our results show that the use of hydrochars as amendment in arable field or horticultural pot production will require an adjustment of N‐mineral‐fertilization strategies.