Efficacy of rapeseed residue and eggshell waste on enzyme activity and soil quality in rice paddy

Addition of plant residue into soils improves soil physiochemical properties and its fertility. Rapeseed residue is an emerging N source to paddy soils via rice-rape double-cropping practice. The objective of this study was to evaluate the effects of rapeseed residue and eggshell waste on chemical changes and enzyme activity in the rice paddy soil. The powdered eggshells at 0, 1, 3, and 5% were applied once to 7.0 kg paddy repacked soils in each pot treated with the rapeseed residue or the conventional N, P, and K fertilisers. Eight rice seedlings (Oriza sativa L. cv. Ilmibyeo) (40 days after sowing) were transplanted to the treated each pot. The contents of total C (TC) and N (TN), and organic matter (OM) were significantly increased in soils treated with the rapeseed residue compared to the N, P, and K fertilisers. With the addition of eggshell containing ～92% CaCO₃, a considerable increase of soil pH was observed in soils treated with the rapeseed residue and the N, P, and K fertilisers, compared to the untreated soil. Activities of β-glucosidase, urease, and arylsulfatase enzymes were higher in soils treated with the rapeseed residue than soils treated with the N, P, and K fertilisers. The eggshell additions at 1, 3, and 5% into soils treated with the rapeseed residue increased enzyme activity mainly resulting from N mineralisation, whereas no change in enzyme activity was observed in the soils treated with the NPK fertiliser. The combined use of the rapeseed residue and the eggshells can be beneficial to improve soil environment.     

Assessment of land degradation and its impact on crop production in the Dry Zone of Myanmar

Land degradation in terms of soil degradation is a major environmental issue posing threat to sustainable livelihood in the semi-arid region of Central Myanmar. However, the studies on soil degradation status and its impacts in this region are very scanty. The objective of this study was to determine the impact of land degradation on crop production both in terms of area and yield in the Dry Zone of Myanmar. Remote sensing and geographic information system-based modelling was utilized to assess and map soil erosion rates. Household survey was conducted to understand the causes of land degradation and its impacts on crop productivity and livelihoods. It has been found out that the current rate of soil erosion ranged from 0 to 114 t ha^–1 yr^–1, and that the average rate of soil erosion increased from 14.2 to 54.6 t ha^–1 yr^–1 over a period from 2000 to 2012. The major types of land degradation were physical and chemical soil degradation. Farmers identified topographic condition, soil types, improper crop management practices and climatic factors as the main causes of soil erosion. The observed crop yields of monsoon rice, groundnut, sesame and cotton in the highly degraded area were 3–12 times lower compared with the yields of these crops grown in less degraded area. Livelihoods of the farmers in the high-degraded area were affected by crop yield reduction, increased cultivation cost and increased uncultivable land area. The impact of land degradation on crop production was dependent on the severity of degradation. This suggests that advanced conservation measures are immediately required and the supportive policy strategies need to be implemented to educate farmers and to strengthen extension services for sustainable land management in the Dry Zone of Myanmar.     

Emission factors of gaseous carbonaceous species from residential combustion of coal and crop residue briquettes

Experiments were performed to measure the emission factors (EFs) of gaseous carbonaceous species, such as CO₂, CO, CH₄, and non-methane volatile organic compounds (NMVOCs), from the combustion of five types of coal of varying organic maturity and two types of biomass briquettes under residential burning conditions. Samples were collected in stainless steel canisters and 2,4-dinitrophenylhydrazine (DNPH) cartridges and were analyzed by GC-FID/MS and HPLC, respectively. The EFs from crop residue briquette burning were generally higher than those from coals, with the exception of CO₂. The dominant NMVOC species identified in coal smoke were carbonyls (41.7%), followed by C2 unsaturated hydrocarbons (29.1%) and aromatics (12.1%), while C2 unsaturated hydrocarbons were the dominant species (68.9%) emitted from the combustion of crop residue briquettes, followed by aromatics (14.4%). A comparison of burning normal crop residues in stoves and the open field indicated that briquettes emitted a larger proportion of ethene and acetylene. Both combustion efficiency and coal organic maturity had a significant impact on NMVOC EFs from burning coal: NMVOC emissions increased with increasing coal organic maturity but decreased as the combustion efficiency improved. Emissions from the combustion of crop residue briquettes from stoves occurred mainly during the smoldering process, with low combustion efficiency. Therefore, an improved stove design to allow higher combustion efficiency would be beneficial for reducing emissions of carbonaceous air pollutants.     

甘肃省陇东塬区土壤及农作物中微量元素的分布特征

通过测定甘肃省陇东塬区马岭、西峰和华庆油田区土壤以及小麦、苹果、油菜中Cu、Ni、Cd、Pb、Cr、Zn等6种微量金属元素质量分数,研究塬区土壤中微量元素的空间分布特征及其在植物体内的转移、富集能力.结果表明:塬区土壤中w(Zn)明显高于其他5种元素,其平均值达111.64 mg/kg;w(Cd)最小,在1.64～3.38 mg/kg之间;其余4种元素(Cr、Pb、Ni、Cu)质量分数在20～70 mg/kg之间.当地主要农作物对土壤中微量元素的富集系数均小于1,富集能力一般,其中根部的富集能力相对较大,地上部位均较小.      

滨海滩涂不同围垦年代垦区农作物重金属累积特征及其与氮、磷的关系

为探明滨海滩涂围垦区农作物重金属累积特征及其与围垦年代、作物氮磷含量及化学计量比的关系,采集盐城地区不同围垦年代(围垦20、30、40、60年)农田4种主要作物(大麦、小麦、油菜、蚕豆)样品63个,测定了其根、茎叶和籽粒中Cd、Cu、Zn、Pb、Hg、As及全氮(N)、全磷(P)和粗蛋白(CP)含量,分析了重金属累积特征及与围垦年代、N、P、CP及N/P比的关系,并采用单因子污染指数法和内梅罗综合污染指数法对重金属污染程度和安全水平进行了评价。结果表明,1)围垦农田作物整株各指标含量分别为Cd (0.52±0.94)、Cu (12.98±16.00)、Zn (34.93±27.91)、Pb (3.50±5.88)、Hg (0.0063±0.0063)、As (1.94±3.72) mg·kg~(-1)及N(13.69±8.27)、P (5.98±2.24)、CP (79.55±49.54) g·kg~(-1);籽粒中则分别为(0.0059±0.020)、(1.83±1.48)、(11.13±4.45)、(0.09±0.30)、(0.0023±0.0036)、(0.0021±0.0048) mg·kg~(-1)及(19.21±7.68)、(6.04±1.64)、(111.78±47.81) g·kg~(-1); 2)作物重金属均表现为根茎叶籽粒,N和CP与之相反,表现为根茎叶籽粒,而P则表现为根籽粒茎叶; 3)不同围垦年代之间作物重金属、N、P、CP含量、N/P比及综合污染指数(Pz)均没有显著差异(P0.05); 4)各作物籽粒6种重金属单因子污染指数均值均小于1,除个别样品Pb超标(超标率11%)外,其他重金属均未超标; 5)作物籽粒重金属Pz均值为0.38,表明该地区作物重金属总体处于安全级,但大麦、小麦、油菜籽粒均有样品Pb含量超过警戒线,个别样品甚至达到重度污染水平; 6)作物整株各重金属之间、重金属与P之间均存在显著正相关(P0.01),而重金属与N、CP、N/P存在显著负相关(P0.01),在籽粒中则相关性均不显著(P0.05)。以上结果显示,盐城滨海滩涂围垦区作物重金属累积与围垦时间关系不大,其含量目前尚处于可接受范围内,但Pb污染值得关注,作物重金属与P之间存在一定的相互促进作用,而与N存在一定的拮抗作用,高氮低磷的机体养分状况有助于降低重金属含量。     

哈尼梯田地区农户粮食作物种植结构及驱动力分析

哈尼稻作梯田系统作为全球重要农业文化遗产（GIAHS）,具有极高的生态、经济、文化价值。近年来,以粮食产量增长为导向的农耕技术和作物品种单一化趋势,给哈尼梯田地区带来了严重的生态和食品安全问题。论文以农户生产行为作为切入点,从主要粮食作物的经济效益、耕地资源特征、村落发展类型、农户的家庭特征与资源禀赋进行实证研究,分析了哈尼梯田地区农户粮食作物种植结构现状及驱动因素。结果表明：1）调查涉及的41.23 hm²有效耕地中,按种植总面积排序,杂交稻、玉米、水果类作物位居前三。2）本地传统粮食作物--梯田红米,种植总面积和户均种植面积远小于经济效益较高的杂交稻和兼有饲料用途的玉米。同时,农户倾向于将其种植在质量较差、海拔较高的耕地上。3）作物的经济效益和耕地海拔及质量对替代性作物（如杂交稻和红米）的种植选择影响较大;个体农户层面上,农户特征与资源禀赋在不同程度上对不同作物的种植选择产生影响。     

成都平原氮磷化肥施用强度空间分布及影响因素分析

掌握化肥施用强度的空间分布及影响因素,对施肥的精准管理和污染防控意义重大.以往研究多限于人为因素的探讨而缺乏自然地理因素对化肥施用强度空间分布的影响分析.基于成都平原23492个点位的化肥调研数据,结合地统计学方法和地理信息系统（GIS）技术,探究该区域2010~2015年均氮和磷化肥施用强度的空间分布特征及影响因素.结果表明：①研究区2010~2015年均氮和磷化肥施用强度总体处于120~360 kg·hm^-2和60~180 kg·hm^-2的中低风险强度.高风险强度主要分布在郫都、彭州、什邡、龙泉驿和金堂等粮（果）蔬种植区,相对低值区多分布在南部和东北部;②氮和磷化肥施用强度的块金系数为66.17%和41.60%,其空间分布受结构性和随机性因素共同作用决定,呈中等空间自相关性;③人为和自然因素均对氮和磷化肥施用强度的空间分布影响显著.种植作物类型（细分类）能独立解释12.90%和25.10%的施氮和施磷空间变异,是影响氮和磷施用强度空间分布的主控因子;成土母质的重要性仅次于种植作物类型,且对于施磷强度独立解释能力约是施氮强度的3.6倍.在种植作物类型起主要决定作用时,成土母质仍深刻制约和影响研究区氮和磷化肥施用强度的空间分布.因此,进行化肥施用管理和环境风险分析时需重点考虑种植作物类型和成土母质的综合作用,在磷肥施用方面更应关注成土母质的影响.     

中国各区域秸秆资源可能源化利用的潜力分析

在我国能源需求迅速增长并日益依赖国际市场的背景下,能源化利用秸秆资源是我国缓解能源短缺的重要选择之一。论文在综合相关研究成果的基础上,对我国不同区域农作物秸秆可能源化利用的潜力及资源密度进行了分析。研究表明,2009年中国农作物秸秆理论资源量为7.48×10⁸ t,可获得资源量为6.34×10⁸ t,可能源化利用量为1.52×10⁸ t。中国可能源化利用秸秆资源区域分布极不均匀。长江中下游、东北、华北等区域可能源化利用秸秆潜力较大,分别为0.42×10⁸、 0.37×10⁸和0.35×10⁸ t,青藏高原、黄土高原和西南可能源化利用秸秆资源潜力较低。根据各区域可能源化利用秸秆资源密度,论文对不同省份建造较大规模秸秆发电企业或燃料乙醇企业的适宜性进行了分析。     

论全球生态经济系统的不可持续性——基于农业生态系统承载力视角

运用3种方法预测的作物产量潜力分别为：（1）利用作物历年单产回归拟合后进行趋势外推,得出多数作物的未来产量潜力极限大约将是现在单产的2～3倍;（2）运用＂国际应用系统研究所＂（IIASA）与＂联合国粮农组织＂（FAO）共同开发的＂农业生态区划＂（AEZ）模型计算我国主要粮油作物的区域单产最高潜力,得出水稻、小麦、玉米、马铃薯、油菜和大豆的单产潜力分别是它们2005年全国平均单产的1.2、2.2、2.2、2.9、2.0、1.9倍;（3）运用自然界中植物的最大光能利用率计算世界主要粮油作物单产的光合潜力,得出水稻、小麦、玉米、马铃薯、油菜、大豆产量的最大光合生产潜力大约分别是目前高产地区单产的1.4、2.5、1.2、1.8、1.9、2.2倍。据此：从作物产量潜力极限出发,阐述了农业生态系统的承载力;再从＂封闭＂系统特性出发,论述了全球生态经济系统的不可持续性。人类所能做的是尽力延缓＂终点＂的出现：行动越早,效果越好。     

吉林省主要覆膜作物地膜残留情况调查

通过文献调研、问卷调查和典型样点采集的方法对吉林省3种主要覆膜作物的地膜残留情况进行调查分析,结果表明：地膜残留量与覆膜年限、地膜回收方式以及种植作物种类密切相关。随覆膜时间的延长地膜残留量有增加的趋势。3种模式地膜残留量由高到低为：瓜菜模式〉玉米连作模式〉花生连作模式,连续覆膜10年,3种模式的地膜残留量分别为30、28.35 kg·hm^-2和15.9kg·hm^-2。以一级污染水平作为标准（75 kg·hm^-2）,覆膜量每年按75～150 kg·hm^-2、年残留率按1.2%～4.02%计,估算吉林省安全使用地膜的年限约为12～83年。