长期秸秆还田对潮土真菌群落、酶活性和小麦产量的影响

为了研究秸秆还田对黄淮海平原潮土真菌群落的影响,开展连续10 a田间定位试验,设置不施肥（NF）、单施化肥（NPK）和秸秆还田配施化肥（NPKS）这3个处理,通过网络分析和结构方程模型,揭示真菌群落对土壤肥力、酶活性和小麦产量的影响机制.结果发现,NPKS处理土壤有机质（SOM）较NPK处理和NF处理分别升高9.20%和34.75%,碱解氮（AN）升高12.03%和39.17%,脱氢酶（DHA）升高37.21%和50.91%,β-葡糖苷酶（β-GC）升高17.29%和73.48%,小麦增产16.22%和125.53%.不同施肥处理真菌α-多样性并未发生显著变化,却导致β-多样性出现明显分异.冗余分析表明,速效磷（AP）、SOM和AN是潮土真菌群落组成变化的主要调控因素.差异物种分析表明,NF处理富集了Mortierella、Aspergillus、Ceriporia和Acremonium等具有溶磷/解钾功能的物种,以及Leohumicola和Hyalodendriella等植物共生菌;NPK处理中Sarocladium、Fusarium和Fusicolla等植物病原菌丰度显著升高;NPKS处理则激发了Pseudogymnoascus和Schizothecium等抑病菌生长,并提高Trichocladium和Lobulomyces等秸秆降解物种丰度.网络分析发现整个网络由4个主要模块组成,其中模块2物种累积丰度在NPKS处理显著升高,且与DHA和β-GC呈线性正相关关系.结构方程模型结果进一步表明小麦产量主要受SOM直接正向调控,而模块2物种可通过正向调节DHA和β-GC,间接影响SOM和小麦产量.综上所述,黄淮海平原潮土区秸秆还田可通过调节真菌种间互作关系,刺激特定物种集群生长,抑制病原菌活性,提高土壤酶活性,促进SOM累积,最终获得作物高产.     

秸秆还田配施化肥对土壤养分及冬小麦产量的影响

为探究关中地区秸秆还田配施化肥对土壤养分和冬小麦产量的影响,研究采用裂区试验设计,主区为：秸秆不还田（S₀）和秸秆还田（S）;副区为：不施肥（WF）、氮肥（NF）和氮磷肥（NPF）.应用生态化学计量的方法,探究秸秆还田配施化肥下土壤碳氮磷含量变化及其和产量的关系.结果表明,秸秆和施肥互作对表层（0~20 cm）土壤有机碳、全氮和全磷含量均产生显著影响（P<0.05）.与S₀WF处理相比,SNPF处理显著提高表层（0~20 cm）土壤有机碳和全氮含量（P<0.05）.秸秆和年份互作对表层（0~20 cm）土壤全氮含量产生显著影响（P<0.05）,随着秸秆还田时间的增加,在2021年SWF处理下表层（0~20 cm）土壤全氮含量显著高于S₀WF （P<0.05）.秸秆和施肥及其互作对20~40 cm土层有机碳和全氮含量无显著影响（P>0.05）,但对20~40 cm土壤全磷含量产生显著影响（P<0.05）,与SWF处理相比,SNPF处理显著增加了20~40 cm土层全磷含量（P<0.05）.秸秆还田配施化肥对土壤化学计量特征也产生显著影响.与S₀WF处理相比,S₀NPF处理能够降低表层（0~20 cm）土壤C：N,提高表层（0~20 cm）土壤C：P和N：P.与SWF处理相比,SNF处理能够降低表层（0~20 cm）土壤C：N.秸秆还田配施化肥对冬小麦产量也产生显著影响,2020年和2021年SNPF处理与S₀WF处理相比分别增产24.23%和28.9%.相关性分析表明,产量与C：N （P<0.05）和C：P （P<0.01）呈显著正相关关系.全氮和N：P与处理年份呈极显著正相关关系（P<0.001）.综上所述,在关中地区秸秆还田配施氮磷肥处理（SNPF）会改善土壤养分,改变土壤化学计量特征,同时提高产量.因此,本研究结果表明秸秆还田配施氮磷肥（SNPF）是优化区域农田养分管理,提高粮食生产能力的有效途径.     

秸秆还田、地膜覆盖及施氮对冬小麦田N2O和N2排放的影响

为探究不同耕作方式及施氮水平下黄土高原地区旱地冬小麦田N₂O排放规律,运用静态箱-气相色谱法研究了冬小麦田N₂O排放动态.以冬小麦‘小偃22’为材料,采取双因素裂区试验设计,主区为3种耕作模式：常规耕作（CT）、秸秆还田（SM）和平膜覆盖（FM）;副区为3种氮水平处理：不施氮、减氮20%(144 kg·hm^-2)和常规施氮(180 kg·hm^-2).以常规耕作（CT）为对照,探讨不同施氮水平下FM和SM对土壤N₂O排放产生的影响,同时分析环境因子与N₂O排放通量的相关性,并根据经验公式估算N₂排放量.结果表明,各施氮处理的土壤N₂O的排放主要集中在施肥后20 d内,且N₂O排放通量峰值出现在施肥后两周之内.冬小麦田的平均N₂O通量为1.92～22.75μg·（m²·h）^-1,累积排放量为0.10～0.46 kg·hm^...     

An effective approach to improve ethanol productivity by simultaneous saccharification and fermentation of rice straw

Fuel ethanol was produced using rice straw with the simultaneous saccharification and fermentation (SSF) method. The influence of cellulose liquefaction pretreatment and Fe²⁺ quantity on ethanol productivity was investigated in detail. At the same time, the optimized conditions including fermentation temperature, Fe²⁺ amount, yeast inoculation quantity, and the inoculated cellulose enzyme dosage in the SSF process were systematically investigated by analyzing fuel ethanol yield. The result indicated that fuel ethanol yield was 0.319 g per gram rice straw by SSF approach when appropriate amount of Fe²⁺ was added into the reaction system. The optimal technology parameters were: fermenting temperature of 36°C, Fe²⁺ amount of 4 mg · g^?1, inoculating proportion of 20%, cellulose enzyme of 20 IU · g^?1, and Pachysolen tannophilu/saecharomyces cerevisiae of 1:2 ratio. The ethanol yield under the best conditions was larger than that of the control group. We hope that this research can facilitate to achieve large-scale comprehensive utilization for rice straw.     

Energy balance and global warming potential of corn straw-based bioethanol in China from a life cycle perspective

As the second largest corn producer in this world, China has abundant corn straw resources. The study assessed the energy balance and global warming potential of corn straw-based bioethanol production and utilization in China from a life cycle perspective. The results revealed that bioethanol used as gasoline and diesel blend fuel could reduce global warming potential by 10%–97% and 4%–96%, respectively, as compared to gasoline and diesel for transport. The total global warming potential, net global warming potential, net energy, and Net Energy Ratio per MJ ethanol generated from corn straw-based bioethanol system are estimated to be 0.20 kg CO₂-eq, 0.012 kg CO₂-eq, 0.60 MJ, and 1.87, respectively. By using sensitivity analysis, we found that the collected coefficient and compressing density of straw have a more obvious influence on energy balance; transportation distance has a more obvious influence on global warming potential emission factor. The by-products may be utilized as fertilizer, animal feed, cement replacement, or high-value lignin chemicals, which make a contribution to offsetting 0.28 MJ per MJ ethanol of energy consumption.     

稻草浸泡液对藻类抑制作用机制

室内研究了不同降解方式和降解时间的稻草浸泡液对铜绿微囊藻生长的抑制效果及其抑藻机制.结果表明,稻草本身存在抑藻活性物质,低温浸泡4 d的无菌稻草液在2.5 g/L投加量下,对微囊藻的抑制作用达到了69.3%.在稻草浸泡液抑藻过程中,稻草产生的化学物质作用和生物作用同时存在,其相对大小取决于稻草的降解方式和降解时间.对于厌氧降解浸泡液而言,主要通过化学物质的作用抑藻,其抑藻效果随稻草厌氧降解时间的延长明显减弱,如厌氧浸泡15　d和30 d的稻草液在1.5 g/L浓度下其抑制率分别为83％和46％;好氧降解浸泡液主要通过生物作用抑藻.其抑藻效果随稻草好氧降解时间的延长而增强,如1.5 g/L投加量下,15和30 d好氧降解带生物相的稻草浸泡液对微囊藻的抑制率分别为81％和93％.     

稻秸沼渣矿化特征及对青菜生长和品质的影响

以稻秸沼渣和商品有机肥为原料,采用室内培养和盆栽实验方法,研究了稻秸沼渣中碳、氮等养分释放特性以及对蔬菜产量和品质的影响.结果表明,稻秸沼渣施入土壤后可明显提高土壤有机碳矿化速率和微生物生物量碳,秸秆发酵半年的沼渣的矿化特性优于发酵一年的秸秆沼渣.秸秆沼渣有机氮的矿化特性主要表现为氮的固定,秸秆厌氧发酵越充分,沼渣矿化时有机氮越不容易被固定.相比商品有机肥,添加稻秸沼渣青菜的产量略低,但显著提高了青菜中维生素C和水溶性糖含量,降低了硝酸盐含量,提高了青菜品质.因此,秸秆沼渣农肥化对提高蔬菜产量和品质有很好的效果.     

长期秸秆还田对塿土耕层土壤有机碳库的影响

在关中平原塿土(土垫旱耕人为土)上施用化肥的条件下,进行不同用量玉米秸秆直接还田(低秸9 375 kg·hm^-2,中秸18 750 kg·hm^-2,高秸37 500 kg·hm^-2)、间接还田(厩肥,37 500 kg·hm^-2)的长期定位试验21 a,观测和分析了耕层土壤有机碳的储量及氧化稳定性等的变化。结果显示,与单施化肥相比,秸秆直接或间接还田均可显著提高土壤有机碳含量,耕层土壤有机碳储量分别增加了12%(低秸)、24%(中秸)、41%(高秸)和39%(厩肥)。施用秸秆和厩肥21 a,土壤有机碳累积系数平均分别为5.6%和7.2%。秸秆直接还田和厩肥均使土壤有机碳的氧化稳定性降低,胡敏酸的能态升高且保持相对稳定。以上结果表明,秸秆直接或间接还田不仅能显著提高土壤有机碳储量,也能明显改善土壤有机碳的活性和质量,是提高农田固碳能力、促进农业可持续性的重要措施。     

Online single particle analysis of chemical composition and mixing state of crop straw burning particles: from laboratory study to field measurement

Fresh straw burning (SB) particles were generated in the laboratory by the combustion of rice straw and corn straw. The chemical composition and mixing state of the fresh SB particles were investigated by an Aerosol Time-of-Flight Mass Spectrometer (ATOFMS). Based on the mass spectral patterns, the SB particles were clustered into four major types: Salt, Organic Carbon (OC), Elemental Carbon (EC), and internally mixed particles of EC and OC (EC-OC). In addition, particles containing ash, polycyclic aromatic hydrocarbons, heavy metals or nicotine were also observed. Physical and chemical changes of the SB particles immediately after the emission were analyzed with highly time-resolved data. During the aging processes, the average particle size increased steadily. Freshly emitted organic compounds were gradually oxidized to more oxygenated compounds in the OC-containing particles. Meanwhile, an important displacement reaction (2KCl+ SO42−→ K₂SO₄ + 2Cl⁻) was observed. The marker ions for SB particles were optimized and applied to identify the SB particles in the ambient atmosphere. The fluctuation of the number fraction of ambient SB particles sorted by ATOFMS agrees well with that of water soluble K⁺ measured by an online ion chromatography, demonstrating that the optimized marker ions could be good tracers for SB particles in field measurements.     

外源葡萄糖对麦秸厌氧发酵产沼气的影响

为进一步阐释混合厌氧发酵的内在机制,在中温(35±1)℃条件下,以麦秸为原料,以葡萄糖为外源易分解有机碳,采用批式发酵方式,进行了葡萄糖不同添加量和不同添加方式对秸秆厌氧发酵产沼气影响试验。结果表明,在试验初始添加葡萄糖可提高日产气量,但葡萄糖添加量太少对提高秸秆总固体(TS)产气量无促进作用,当葡萄糖添加量为秸秆TS质量的6%时获得最大秸秆TS产气量,为303.13 m L·g-1,继续增加葡萄糖添加量,秸秆TS产气量反而降低;在秸秆厌氧发酵日产气量下降阶段一次性或者分次添加葡萄糖对促进秸秆厌氧发酵产沼气均无效果,仅在试验初始一次性添加秸秆TS质量6%的葡萄糖时对秸秆厌氧发酵产沼气有促进作用,秸秆TS产气量较对照提高9.24%;添加葡萄糖对秸秆厌氧发酵过程产气中甲烷含量无明显影响,但提高累积产气中甲烷平均含量,且在日产气量下降后添加葡萄糖的效果更好,但这种促进效果与对照间差异并不显著。综合以上结果,在试验初始一次性添加秸秆TS质量6%的葡萄糖可以获得最佳的产气效果。