Short-Term Effect of Nitrogen Intensification on Aggregate Size Distribution, Microbial Biomass and Enzyme Activities in a Semi-Arid Soil Under Different Crop Types

There is a lack of quantitative assessments available on the effect of agricultural intensification on soil aggregate distribution and microbial properties. Here, we investigated how short-term nitrogen(N) intensification induced changes in aggregate size distribution and microbial properties in a soil of a hot moist semi-arid region(Bangalore, India). We hypothesised that N intensification would increase the accumulation of macroaggregates 2 mm and soil microbial biomass and activity, and that the specific crop plant sowed would influence the level of this increase. In November 2016, surface(0–10 cm) and subsurface(10–20 cm) soil samples were taken from three N fertilisation treatments, low N(50 kg N ha~(-1)), medium N(75 and 100 kg N ha~(-1) for finger millet and maize, respectively),and high N(100 and 150 kg N ha~(-1) for finger millet and maize, respectively). Distribution of water-stable aggregate concentrations,carbon(C) and N dynamics within aggregate size class, and soil microbial biomass and activity were evaluated. The high-N treatment significantly increased the concentration of large macroaggregates in the subsurface soil of the maize crop treatment, presumably due to an increased C input from root growth. Different N fertilisation levels did not significantly affect C and N concentrations in different aggregate size classes or the bulk soil. High-N applications significantly increased dehydrogenase activity in both the surface soil and the subsurface soil and urease activity in the surface soil, likely because of increased accumulation of enzymes stabilised by soil colloids in dry soils. Dehydrogenase activity was significantly affected by the type of crop, but urease activity not. Overall, our results showed that high N application rates alter large macroaggregates and enzyme activities in surface and subsurface soils through an increased aboveground and corresponding belowground biomass input in the maize crop.     

基于大数据视域下农业科研院所行政管理体系的改革探究

在现代化的农业科研院所行政管理体系中,融入信息化、便捷化、数字化的大数据理念,可使该体系能够提供更全面、更细致的管理服务,提高行政管理的精准性和管理效率。文章阐述了大数据可助推农业科研院所行政管理体系多元共治的结构创新、有助于优化农业科研院所行政管理体系中的资源配置机制,分析了大数据时代背景下农业科研院所行政管理的现状,从思想观念、管理方式、人事制度、财务体系、行政服务等角度,探讨基于大数据视域下的农业科研院所行政管理体系创新途径。     

玉米秸秆循环流化床气化炉气化工艺参数优化

为实现秸秆类农业生物质废弃物的高效清洁能源化转化利用,采用带有二级返料系统的循环流化床气化炉对玉米秸秆进行了气化试验。在二级返料系统开启及闭合条件下,选取空气当量比为0.20～0.35,研究空气当量比对玉米秸秆气化特性的影响,结果表明二级返料系统开启及闭合两种工况均在空气当量比为0.26时取得较优值,二级返料系统开启时具有较好的气化效果,碳转化率与气化效率最大值分别达到93.54%与77.06%。在二级返料系统开启状态下,试验研究了水蒸气配比对玉米秸秆气化特性的影响,结果表明以空气为主气化介质,辅助以水蒸气气化,可以有效改善气化燃气品质,提升气化效率。当空气当量比为0.26、水蒸气配比为0.2时,玉米秸秆空气—水蒸气气化具有较好的气化特性,燃气热值与气化效率分别达到最大值5.89MJ/m3与81.45%。典型工况条件下的焦油蒸馏馏分分析结果表明,提高气化炉反应温度,并保持一定的水蒸气气化环境,可促进焦油裂解转化。试验可为秸秆类生物质的高效清洁转化利用提供参考依据。     

鸡粪生物炭表征及其对水和土壤镉铅的修复效果

采用缺氧控温法,在200、400、600和800℃条件下制备鸡粪生物炭(BC200、BC400、BC600和BC800),利用比表面积及孔径分析仪(BETacceleratedsurfaceareaandporosimetrysystem)、扫描电镜(scanningelectron microscopy)、透射电镜(transmission electron microscope)、傅里叶红外光谱仪(Fourier transform infrared spectroscopy)等对其理化性质和结构特征进行表征,并研究了鸡粪不同温度处理下生物炭对水体和土壤中Cd、Pb污染修复效果。结果表明,鸡粪生物炭灰分含量、pH值、BET比表面积及孔径随热解温度的升高而增加,表面出现大量无规则的孔隙结构,且以介孔为主,而生物炭产率则随温度升高而显著降低(P0.05)。鸡粪生物炭对Cd2+、Pb2+的吸附分为快速吸附和慢吸附2个阶段,Elovich模型能更好地模拟Pb2+、Cd2+的动力学过程,平衡时最大吸附量分别达到52.02 mg/g (BC600)和242.59 mg/g (BC800)。添加鸡粪生物炭显著提高了土壤pH值(P0.05),而TCLP提取态Pb、Cd含量降低,最大较对照分别降低16.5%和14.5%。与对照相比,鸡粪生物炭不同程度上降低了Pb、Cd弱酸提取态、可还原态以及可氧化态比例,其残渣态比例则分别增加了5.49%～15.14%和2.51%～6.30%。综上所述,鸡粪生物炭对重金属Pb、Cd具有较强的钝化效果。     

膨润土褐铁矿改性白云石催化松木棒气化工艺优化

针对白云石催化剂在生物质催化气化过程中易碎、易产生积碳失活问题,为提高其催化活性、抗积碳和再生性能,采用固定床下吸式气化炉试验系统,以Fe-Dol-Ben(膨润土/褐铁矿改性白云石)为催化剂,松木屑废料经成型为棒状颗粒为原料,进行高温水蒸气催化气化试验。研究气化温度(700～1000℃)、铁含量(质量分数为5%～20%)以及催化剂使用次数(1～4)等因素对松木棒催化气化性能及催化剂表面积碳影响。试验结果表明,水蒸气和松木棒的质量比(气料比)为1,催化剂的铁质量分数为15%,气化温度为900℃时气化气中氢气的体积分数达到最大值58.38%,Fe-Dol-Ben催化剂积碳量随气化温度升高逐渐减小,试验区间内1 000℃时达到最小值,较700℃减少了80%。气化气中氢气的体积分数随铁含量增加呈先增加后降低的趋势,积碳量呈先降低后增加,在铁质量分数为15%催化效果较好。Fe-Dol-Ben催化剂较相同条件下分别用膨润土及改性前白云石催化时积碳量分别减少了80.6%和53.6%。对催化剂进行再生再利用试验表明,使用后的Fe-Dol-Ben催化剂进行700℃煅烧再生后,其晶相与催化前基本相同,将其多次再生循环利用,随着使用次数的增加气化气中氢气的体积分数逐渐降低,催化剂的积碳量逐渐增大,使用4次并用于催化气化时氢气的体积分数仍接近50%,保持较好催化效果。综合气化效果、积碳量及经济性因素,Fe-Dol-Ben铁质量分数为15%,气化温度选取900℃为较理想工况。该研究可为改性白云石Fe-Dol-Ben催化剂的研制及生物质高温水蒸汽催化气化技术提供参考。     

Characterization of biochar and their influence on microbial activities and potassium availability in an acid soil

Application of biochar to soil has increased considerably during recent years because of its effectiveness as a soil amendment causing beneficial effects on soil health. However, the effects have been reported to vary and depend upon types of feedstock and pyrolysis conditions during biochar production. Therefore, characterization of biochar is extremely important for its efficient utilization as a soil amendment. In the present study, biochar was prepared from agro-industrial by-products (rice husk and sugarcane bagasse) and weeds (Parthenium and Lantana) under similar pyrolysis conditions. Lantana biochar (LBC) showed the highest pH (10.4) while the lowest value (8.5) being recorded in rice husk biochar (RHBC). The energy-dispersive X-ray spectroscopy (EDS) analysis indicated that LBC and Parthenium biochar (PBC) were superior with respect to potassium (K) content than sugarcane bagasse biochar (SBBC) and RHBC. The Fourier-Transform Infrared Spectroscopy (FTIR) study exhibited the existence of different functional groups in biochar. All the biochar treated soils showed significantly higher microbial activities with different degrees. Application of LBC and PBC at 4.50 g kg^?1 soil significantly increased K availability in soil. Lantana biochar and PBC amended the soil at 9 g kg^?1 significantly increased the soil pH thus makes these biochar as potential liming materials.     

Influence of nitrogen application on dry biomass allocation and translocation in two maize varieties under short pre-anthesis and prolonged bracketing flowering periods of drought

Plants have evolved different mechanisms to survive under stress conditions. This field study was conducted to evaluate the influence of nitrogen (N) application on dry biomass allocation and translocation in two maize varieties under short pre-anthesis and prolonged bracketing flowering period of drought. Two maize varieties, ‘Pioneer 30B80? and ‘Suwan 4452? receiving N at 0 (control), 160 (optimal) and 320 (supra-optimal) kg ha^?1 were subjected to short pre-anthesis and prolonged bracketing flowering periods of drought. Prolonged bracketing flowering period of drought had more suppressive effect on anthesis-silking interval, dry matter allocation and translocation, leaf greenness, contribution of current assimilates to grain (CCAG), kernel number, kernel weight and kernel yield of two maize varieties than a short pre-anthesis drought. Nitrogen application at optimal level was the best for all traits, except CCAG. The maize variety ‘Pioneer 30B80? performed better under both drought types due to more root xylem vessels of large size and more accumulation of dry matter in leaves and roots than the variety ‘Suwan 4452?. Therefore, the variety ‘Pioneer 30B80? may be planted in drought prone environments and may be used in breeding program aimed at developing drought-tolerant cultivars.     

广东主要乡土阔叶树种单木生物量生长模型

【目的】选择广东主要乡土阔叶树种樟树Cinnamomum camphora、木荷Schima superba和枫香Liquidambarformosana为研究对象,建立3个树种的单木生物量生长模型,快速精确计量和监测森林碳汇造林项目的碳储量变化。【方法】每个树种按10个径阶均匀分配伐倒90株样木(共270株),以样木的生物量数据为单木生物量,以立木年龄为自变量,分别建立不同起源(天然林和人工林) 3个树种的地上和地下4种方程生物量生长模型,并选择最优模型通过联立方程组总量控制法解决地上各组分(干材、树皮、树枝、树叶)的生长模型相容性问题。【结果】天然林和人工林起源条件下,相同树种在同一生物量生长模型形式下生物量增长的上限值和最大增速年龄均有差异。各方程在相同起源和树种条件下所得的生物量上限和拐点年龄差异明显。估计地上生物量时,各树种最优方程形式不同。选择Logistic方程对3个树种地上各组分生物量联立方程组建立相容性生长模型,3个树种干材生物量方程的R_(adj)~2为0.560～0.768,平均预估误差(MPE)为3.05%～6.73%;树皮生物量方程的R_(adj)~2为0.552～0.866,MPE为2.02%～6.27%;树枝生物量方程的R_(adj)~2为0.309～0.706,MPE为3.01%～14.33%;树叶生物量方程的R_(adj)~2为0.495～0.767,MPE为4.16%～7.14%。【结论】比较4种模型的参数及评价指标可知,地上生物量生长最优模型为Logistic方程,地下生物量生长最优模型为Schumacher方程。地上各组分生物量在立木生长的周期中占地上总生物量的比例随着年龄的增长而不断变化。选择Logistic方程对3个树种地上各组分生物量联立方程组建立相容性生长模型,干材和树皮的生物量方程拟合效果相对于树枝和树叶更好。该模型主要适用于在已知年龄的人工碳汇造林的生物量估计;结合含碳系数,可预估未来一定时期内的碳储量及碳汇量。     

青冈栎混交林生物量及碳储量分布特征

以湖南永顺43年生青冈栎混交林为研究对象,采用平均木法和样方收获法测定乔木层生物量和林下植被层生物量,采用重铬酸钾—水合加热法测定样品碳素含量,对林分各组分的生物量和碳储量分布特征进行研究。结果表明:青冈栎混交林单位面积生物量为320.03t/hm~2,各组分单位面积生物量由大到小的排列顺序为乔木层、枯落物层、灌木层和草本层。林分单位面积碳储量高达389.43t/hm~2,其中植被层和土壤层分别为249.02,140.41t/hm~2。林分内青冈栎、栲树和杉木单株平均蓄积分别为0.156 1,0.2912,0.296 0m~3,单株平均碳储量分别为103.85,99.15,97.90kg。青冈栎属于生长速度较慢但木材密度大的树种,单株平均蓄积仅有栲树和杉木的单株平均蓄积的1/2左右,但其单株平均生物量和碳储量却比栲树和杉木的单株平均生物量和碳储量要高,表明树种碳汇能力的高低并不完全取决于树种生长速度的快慢,这对今后生态公益林树种的选择提供了一个新的方向。     

等高反坡阶对滇中云南松林乔木层碳储量及碳增量分配格局的影响

通过标准地调查和生物量实测相结合的方法,对布设等高反坡阶后滇中云南松林乔木层碳含量、生物量、碳储量及分配特征进行了估算,并分析了8年后各器官碳增量及分配格局特征。结果表明:布设等高反坡阶后云南松各器官碳含量变幅为41.01%～47.35%,平均碳含量高低排列依次为干叶枝皮粗根中根细根。10～15龄的云南松林在布设等高反坡阶后地上部分总生物量比对照高32.75%,等高反坡阶显著提高了10～15龄和15～30龄地下部分生物量(30.73%和35.71%),总生物量随着龄组的增加而显著增加。等高反坡阶显著提高了10～15龄云南松林地上部分碳储量(32.79%)和15～30龄地下部分碳储量(35.60%);布设等高反坡阶8年后显著增加了10～15龄、15～30龄地上部分碳增量(53.33%和20.45%)和地下部分碳增量(53.70%和73.43%)。综上,人工造林时应对等高反坡阶予以高度关注,适度发展等高反坡阶措施,在等高反坡阶基础上因地制宜地进行人工造林,增加山地造林面积和植被碳储量,从而保护当地生态环境。