施氮对稻麦轮作系统综合增温潜势的影响

采用典型区域田间试验结合生物地球化学模型（DNDC模型）,以上海市崇明岛为例对稻麦轮作系统作物产量和温室气体排放进行了模拟研究。结果表明：DNDC模型能较好地模拟田间实测到的稻麦轮作系统温室气体排放通量。在常规用量的80%~150%之间增施氮肥对作物产量无显著增加,但稻麦轮作系统综合温室效应呈递增趋势。东滩农业园区稻麦轮作系统最优施氮量为常规用量的6298%,此时单位产量增温潜势（Global Warming Potential,GWP）最小,作物产量为12 8775 kg/(hm2〖DK〗·a),综合温室效应较常规施氮降低3670%。长江下游地区稻麦两熟制农业生态系统能够通过合理控制农田氮肥用量减少温室气体排放净通量,降低作物单位产量GWP     

Spatial and temporal projected distribution of four crop plants in Egypt

This study focuses on the management of the local agroecosystems in order to adapt planting or sowing practices for the projected climate change scenarios. It is projected that there will be increased air temperature throughout all four seasons in the coming 100 years, from the southern towards the northern parts of Egypt. The objective of this study is to investigate the influence of that increased air temperature on the spatial and temporal distribution of four of the major economic crops in Egypt. The study species are cotton (Gossypium barbadense L., cv. Giza 89), wheat (Triticum aestivum L., cv. Gemiza 9), rice (Oryza stiva L., cv. Sakha 101) and maize (Zea mays L., cv. Hybrid 10). Optimum air temperature allowing maximum growth for each of the study crop cultivars and the current and projected air temperature patterns in the future years were used for projection of the seasonal and crop distribution maps in the years 2005, 2025, 2050, 2075 and 2100. Results showed that sowing dates of a target crop may be managed in order to allow maximum predicted planting area in the same region. The current maximum area suitable for planting the Cotton crop in Egypt (104 thousand Fadden/year; one Fadden = 0.96 hectare or 0.42 acre) showed few variations over the coming hundred years. In this case, the sowing dates should be changed from the hotter months (February to April) to the cooler months (January to February). Alternatively, a great reduction in the area planted by Wheat crop was predicted in the coming 100 years. Despite the early planting, a reduction of about 147 thousand Fadden/year was projected by the year 2075. On the other hand, with earlier sowing dates, the maximum areas that are planted by Rice and Maize may not be greatly affected by the projected increase in air temperature.     

The Potential of Soil Carbon Sequestration Through Improved Management Practices in Norway

The study was conducted to assess the potential of Norwegian agricultural ecosystems to sequester carbon (C) based on the data from some long-term agronomic and land use experiments. The total emission of CO₂ in Norway in 1998 was 41.4 million metric ton (MMT), of which agriculture contributed only 0.157 MMT, or <0.4% of the total emissions. With regards to methane (CH₄) and nitrous oxide (N₂O) gases, however, agricultural activities contributed 32.5% and 51.3% of their respective emissions in Norway. The soil organic carbon (SOC) losses associated with accelerated soil erosion in Norway are estimated at 0.475 MMTC yr^–1. Land use changes and soil/crop management practices with potential for SOC sequestration include conservation tillage methods, judicious use of fertilizers and manures, use of crop residues, diverse crop rotations, and erosion control measures. The potential for SOC sequestration is 0.146 MMTC yr^–1 for adopting conservation tillage, 0.011–0.035 MMTC yr^–1 for crop residue management, 0.026 MMTC yr^–1 for judicious use of mineral fertilizer, 0.016–0.135 MMTC yr^–1 for manure application, and 0.036 MMTC yr^–1 for adopting crop rotations. The overall potential of these practices for SOC sequestration ranges from 0.591 to 1.022 MMTC yr^–1 with an average value of 0.806 MMTC yr^–1. Of the total potential, 59% is due to adoption of erosion control measures, 5.8% to restoration of peat lands, 21% to conversion to conservation tillage and residue management, and 14% to adoption of improved cropping systems. Enhancing SOC sequestration and improving soil quality, through adoption of judicious land use and improved system of soil and crop management, are prudent strategies for sustainable management of soil, water and environment resources.Readers should send their comments on this paper to: bhaskarn ath@aol.com within 3 months of publication of this issue.     

双季稻区冬种覆盖作物对土壤微生物量的影响

利用氯仿熏蒸浸提法研究了南方双季稻区4种冬季覆盖作物对土壤微生物量碳、氮周年动态的影响.结果表明:冬季种植紫云英(Astragalus sinicus L.)、黑麦草(Lolium multiflroum Lam.)和马铃薯(Solanum tuberosum L.)土壤微生物量碳含量分别为:248.8mg·kg-1、256.7mg·kg-1和238.9mg·kg-1均显著高于冬闲田的218.3 mg·kg-1(P<0.05),增幅为9.43%～17.59%;冬季种植油菜(Brassica campestris L.)土壤微生物量碳比冬闲田提高了0.63%,没有显著性差异.4种覆盖作物土壤微生物量氮含量分别为:紫云英,100.3 mg·kg-1、黑麦草,153.8 mg·kg-1、马铃薯,99.9 mg·kg-1和油菜,86.2 mg·kg-1,均显著高于冬闲田,73.5 mg·kg-1(P<0.05).对比冬闲田,各个覆盖作物均显著提高土壤有机质含量(P<0.05).说明种植冬季覆盖作物可以提高土壤有机质含量和有效养分含量,促进了土壤微生物的活动,有利于保持土壤肥力.     

Estimation of crop residue in China based on a Monte Carlo analysis

Accurate crop residue resource estimation is important for bioenergy development.This is done by the ratio of residue to grain(R/G),which is usually regarded constant and is widely used for crop residue estimation though uncertainty is inevitable in practice.In this study,a Monte Carlo algorithm was applied to estimate national crop residue by R/G taken from published reports in China.The estimated result was further mapped in pixels by geographic information system.In2009,the amount of crop residue was found to be 802.32 million tons(Mt),with 679.36 and 947.28 Mt as the lower and upper limits for 95%confidence limits.Chinese crop residue was dominated by rice,wheat,and corn,accounting for74.57%(598.29 Mt).From 1949 to 2009,the amount of crop residue increased by four times,accompanied by component change.The spatial distribution of crop residue in China is markedly heterogeneous.Compared to the shortage of crop residue in northwest China,there is an abundant crop residue of about 334 Mt in eastern China,attracting 90%of the country's electricity or heat generation plants.     

塔里木盆地东南缘绿洲区土壤砷空间分布及农作物砷富集特征

以新疆塔里木盆地东南缘的巴音郭楞蒙古自治州的若羌县、且末县和和田地区的民丰县、于田县的绿洲区为研究区,采集表层土壤3487组、土壤剖面采样点35组,农产品及根系土壤采样点93组,综合采用数理统计方法、地统计学和GIS技术,研究土壤As的空间分布特征,探讨各类农产品对As富集的影响,比较空间自相关性显著区域和空间自相关性无显著区域内农产品和根系土壤中As的含量特征.结果表明土壤As含量较低,农用地和非农用地土壤As含量均值分别为9. 81mg·kg~(-1)和7. 94 mg·kg~(-1).表层土壤As含量超过新疆土壤背景值的采样点个数为568个,占总取样点数的16. 3%;超过风险筛选值的采样点个数为5个.土壤As空间自相关的莫兰指数均大于0,空间聚集类型主要以高-高型和低-低型为主,其中高-高型聚集区主要位于各县农用地范围内.GIS空间分布显示,土壤As含量高值区呈片状集中或岛状零散分布.标准差椭圆显示,若羌县土壤As含量变化趋势方向为南北方向,且末县和民丰县土壤As含量变化趋势方向为西南-东北方向,于田县土壤As含量变化趋势方向为西北-东南方向.若羌县农用地土壤垂向剖面上As含量从地表到深层存在波动,其余各县都相对稳定.研究区农作物对As的富集能力表现为:根茎类蔬菜核桃小麦玉米红枣,玉米和红枣的As含量与根系土的As含量在0. 05水平下呈现显著正相关.空间自相关性显著区和空间自相关无显著区的农产品中的As含量无显著性差异,而两个区域根系土壤的As含量存在显著性差异.     

周年轮作休耕对土壤AMF群落和团聚体稳定性的影响

为探究轮作休耕对丛枝菌根真菌（AMF）群落组成及土壤团聚体稳定性的影响,以坡耕地红壤为研究对象,采用Illumina MiSeq高通量测序和湿筛法分别测定AMF群落组成和团聚体,研究了苕子轮作玉米（V-C）、豌豆轮作玉米（P-C）、冬闲-玉米（F-C）和周年休耕（F-F）这4个处理下AMF群落组成及其与土壤养分和团聚体稳定性之间的关系.结果表明,F-F、V-C和P-C处理的>2 mm团聚体含量、R_0.25及MWD均显著高于F-C （P<0.05）,<0.25 mm团聚体含量均显著低于F-C （P<0.05）;F-F处理的ACE、Chao1和Shannon指数较F-C分别显著提高29.56%、35.78%和45.55%;球囊霉属（Glomus）为各处理AMF群落的优势属,盾巨孢囊霉属（Scutellospora）在各处理间差异显著（P<0.05）;PCoA分析发现,PC1和PC2分别累计解释了AMF群落组成差异的29.99%和22.40%;相关性分析表明,盾巨孢囊霉属与碱解氮（AN）和有机质（SOM）呈显著负相关（P<0.05）,与速效钾（AK）呈显著正相关（P<0.05）,球囊霉属与碱解氮呈显著正相关（P<0.05）;RDA分析表明,AMF多样性（Shannon指数）和盾巨孢囊霉属分别与>2 mm和2~1 mm团聚体含量显著正相关（P<0.05）.因此,周年休耕和苕子轮作玉米有利于提高土壤团聚体稳定性和改变AMF群落组成,研究结果为我国南方周年轮作系统提高土壤质量和推行合理轮作休耕模式提供理论依据和参考.     

废弃物基水热炭改良对水稻产量及氮素吸收的影响

生物炭农田回用是实现农林废弃物资源化利用和碳封存的有效手段.近年来,水热碳化技术由于在炭产率、能耗及生产过程中的烟气排放等方面显著优于常规热解碳化技术而受到关注.为实现农林废弃物的资源化利用,明确水热炭农田应用对作物生产力的影响,本研究通过原状土柱模拟试验和表征分析,研究了4种不同类型改良水热炭对两种典型土壤的水稻产量和氮素吸收的影响及可能的驱动因素.结果表明,锯末水热炭和秸秆水热炭经物理或生物改良后,在两种类型土壤上均能够增加水稻产量和氮素吸收,减少氮素损失,且其效应不受水热炭添加量影响（5‰,15‰;质量分数）.与对照相比,水热炭添加处理的产量和氮素吸收量分别提高9.2%~20.7%和7.7%~17.0%.高C/N比的锯末水热炭更有利于高肥力土壤水稻氮素吸收量的增加;而低肥力土壤由于限制性因子较多,受水热炭类型的影响较小.通过对水热炭的表征分析发现,其表面养分元素丰富;水洗或生物改良后其表面孔隙结构有较大改善,C元素相对含量明显降低,N和O元素相对含量明显增加,这对养分的固持/供应可能产生影响.因此,水热炭改良后孔隙结构的改变和N、O元素含量的增加可能是其施用后水稻产量和氮素吸收增加的关键驱动因素.结果说明,水热碳化材料改良后应用农田可以在实现农林废弃物资源化利用的同时,提高作物生产力,减少农田氮素环境损失.     

我国典型秸秆露天燃烧黑碳的高时间分辨率排放特征及其排放清单

农作物秸秆燃烧是大气中黑碳(black carbon,BC)气溶胶的主要来源之一。目前农作物秸秆燃烧排放黑碳的研究主要集中在通过离线样品分析获得的BC排放特征,缺少实时在线排放特征的研究。本研究收集了我国具有代表性的4种农作物秸秆(小麦秸秆、水稻秸秆、玉米秸秆和大豆秸秆),通过在实验室燃烧平台模拟农作物秸秆露天燃烧的过程,利用黑碳仪获得农作物秸秆燃烧过程中BC的实时浓度排放变化;利用质量重建,获得BC在线排放因子。结果表明:农作物秸秆在明燃过程中BC的排放因子较为稳定。通过平均排放因子的计算,获得小麦秸秆、水稻秸秆、玉米秸秆和大豆秸秆的BC排放因子分别为(0.32±0.05) g?kg~(-1)、(0.31±0.13) g?kg~(-1)、(0.31±0.09) g?kg~(-1)和(0.44±0.01) g?kg~(-1)。在排放因子的基础上,结合我国农作物秸秆露天燃烧量,最终建立了2015年我国省级(不含港澳台地区)典型农作物秸秆燃烧的BC排放清单。     

华北平原不同农田管理措施对于土壤碳库的影响

华北平原是我国重要的粮食生产基地,土壤碳氮水平直接作用于区域的土壤肥力和粮食生产.通过长期定位实验,研究了包括自然恢复(F)、清茬翻耕(N)、秸秆还田免耕(S)和秸秆还田翻耕(TS)这4个处理下土壤有机碳(SOC)、无机碳(SIC)、全碳(TS)、全氮(TN)含量和储量以及13C和15N分布状况.结果表明,与F相比,在0~20 cm土层,N、S和TS的土壤有机碳储量分别降低21.6%、12.3%和3.4%,土壤无机碳储量变化不显著.在20~40 cm土层,土壤有机碳储量变化不显著,而3个农田耕作处理的土壤无机碳储量较F分别增加4.1%(N)、7.3%(S)和5.0%(TS),无机碳增加主要是次生碳酸盐的贡献,农田土壤PIC增加了97%~261%.与自然恢复地相比,农田土壤表层δ15N、δ13CSIC、δ13CSOC偏高且δ13CSOC达显著差异,20~40 cm土层δ15N、δ13CSIC偏低而δ13CSOC偏高.该地区农田土壤中原生碳酸盐以分解作用为主,土壤-作物系统通过增加CO_2含量促进次生碳酸盐的形成,秸秆还田是恢复农田耕作引起土壤碳库储存下降的有效措施.对于华北平原,今后应加强关于秸秆还田和耕作措施对土壤有机碳和无机碳影响的综合研究,对于表层以下层次土壤的碳转化和变化规律需要更多的长期观测.