稻鳅共生种养模式试验研究

[目的]稻鳅共生是典型的稻田综合利用模式,符合生态农业发展方向。通过对稻鳅共生生态系统的生理生态学机制开展试验研究,为进一步推广稻鳅共生种养模式提供科学依据。[方法]采用田间试验方法,以水稻单作为对照,研究了不同泥鳅养殖密度下的稻鳅共生对水稻农艺性状、土壤理化性质、水稻产量构成的影响,并对稻鳅共生种养模式进行了经济效益分析。[结果]与对照处理相比,水稻长势在株高、有效分蘖率、根长等方面有一定提高。养殖田水稻株高增高了3%,有效分蘖率提高了8%~11%,根长提高了8.8%~31.3%。在土壤理化性质方面,与对照相比,土壤容重降低了7.1%~21.2%,孔隙度增加了4.1%~14.7%。实验前后养殖田内土壤有机质增加了3.5%~26.5%,对照田降低了2.5%~5.8%。土壤肥力(氮、磷、钾)减少,但减少幅度小于对照处理。稻鳅共生种养模式下水稻产量提高了5%~25%,同时稻田增收泥鳅1 725~3 375kg/hm2,净收入为1.836 0万~2.307 0万元/hm2,经济效益提高了3.65~4.84倍。稻鳅共生种养模式中泥鳅的养殖密度为30万尾/hm2时稻田的生态效益和经济效益最佳。[结论]稻鳅共生有效改善了土壤理化性质,促进了水稻的生长,提高了稻田产量和产值。     

中国农药施用与农业经济增长脱钩状态：时空特征与影响因素

[目的]明确农药施用与农业经济增长关联状态及其影响因素,为实现"控药减害增收"的目标提供借鉴。[方法]基于2005—2015年数据利用脱钩理论和对数平均分解指数法分解进行分析。[结果]中国农业经济增长伴生大量农药施用,仅少数省域表现出农药施用和农业经济增长扩张绝对脱钩的理想状态,东北西北部分省域农业经济增长则以更大幅度的农药投入增长为代价。中西部地区劳动力规模和技术进步效应是推动农药施用与农业经济增长脱钩的因素;东部地区种植规模变化、劳动力规模和技术进步因素均是推动农药施用和农业经济增长脱钩的因素;东北地区仅劳动力规模效应成为推动脱钩的力量。[结论]推动农药施用与农业经济增长脱钩需要强化农业科技的创新与普及,完善农业生产过程中的技术支撑,推动农业病虫害监测预警,加大对环境友好型低污染农药和肥料的推广度;构建农户施药的多重约束机制,完善农业病虫灾害保险减少农户对生产过程的风险感知,发挥农业合作社对农户施药行为的规制作用,完善产品分级认证和安全准入制度;通过农地合理流转和农业机械化等方式集约利用农业生产资源;因地制宜推动农药施用与农业经济增长脱钩,结合区域资源优势和农业发展阶段有针对性地设计对策措施。     

A Meta‐Analysis on the Elasticity of Demand for Pesticides

There is an increasing policy interest in pesticide taxation schemes as a measure to reduce harmful effects of pesticide use. The effectiveness of such tax depends, however, on the price elasticity of demand for pesticides. Moreover, information on these demand elasticities and their determinants is of crucial relevance for policy‐making and normative modeling approaches. In this article, we present a meta‐analysis based on studies that have estimated pesticide demand elasticities in Europe and North America. Our meta‐analysis reveals that the own‐price elasticities of demand for pesticides are, with a median of ?0.28, significantly smaller than zero, but also significantly larger than ?1, i.e. to be inelastic. We find that the demand for pesticides for special crops is less elastic than that for arable and grassland. In addition, the demand for herbicides is more elastic than for other pesticides. Studies that consider only short‐term horizons and little flexibility for farmers to adjust to price changes generate significantly less elastic pesticide demands. The results also indicate that more recent studies identify lower pesticide price elasticities of demand. Furthermore, we find that peer‐reviewed studies tend to find more inelastic results compared to grey literature.     

农田污染对粮食生产的影响研究——以四川为例

作为农业生产的根本,农田质量对于粮食生产而言至关重要,因此农田污染的相关防治已经成为我国农业可持续发展、农产品安全以及我国生态环境保护的重要措施。目前我国农田污染主要特征为农田污染物成分复杂,农田污染程度不断扩大。同时由于农田污染导致土壤肥力下降进而导致相关农作物的产量以及品质不断下降。文章以四川省为例,探究农田污染对粮食生产的影响,结果发现,目前四川省农田污染主要来源于农药化肥的不合理使用,水体以及土壤受工业废水污染严重,畜牧业废弃物污染等。农田污染导致可耕种土地面积不断减少,粮食生产受到严重影响。基于此,该文针对四川省农田污染现状提出农田污染综合立体防控策略,并在此基础上通过合理规划农业生产,减少农药化肥使用量,提高生物防治在病虫害防治当中的比例等措施减少农田污染对粮食生产的影响,以期为我国农田保护以及粮食生产提供一定的理论以及政策依据。     

化学工程与工艺专业面向21世纪人才培养方案研究与实践

化学工程与工艺专业培养高素质、适应21世纪要求的本科教学培养方案,在理论教学、实践环节和课外科技活动等方面进行了系列的整合。整合课程包括人文社科、自然科学、机械、电子与电工、化学、化工、专业特色课程以及工程设计等,基本实现了数学、英语、计算机、工程实践等的不断线,既压缩课时,又有利加强学生综合素质,培养创新能力。     

Access to credit and heterogeneous effects on agricultural technology adoption: Evidence from large rural surveys in Ethiopia

Modern agricultural technologies hold huge potential for increasing productivity and reducing poverty in developing countries. However, adoption levels of these technologies have remained disappointingly low in Africa. This paper analyzes the effect of access to credit on the likelihood of adoption and use intensity of chemical fertilizers using data from large rural surveys in Ethiopia. Using a heteroscedasticity-based identification strategy to address the endogenous nature of access to credit, we find that access to credit has significant positive effects on adoption and intensity of use of chemical fertilizers. However, important heterogeneities are observed. Credit obtained from formal sources is more important for the intensity of use than for the decision to adopt chemical fertilizers. Credit taken with the primary purpose of financing agricultural inputs is more likely to promote adoption of chemical fertilizers than credit taken per se. Furthermore, reported credit effects are larger when estimated against the sample of credit-constrained non-users as compared with the pool of the whole sample of credit non-users. The results remain robust to several sensitivity analyses. Our results yield useful implications for the design, promotion, and targeting of credit services to leverage their effect on adoption of agricultural technologies.     

当前炼化企业清洁生产的特征与措施

通过分析炼化企业清洁生产现状，勾勒出目前炼化企业清洁生产的基本特征，提出清洁生产的主要对策措施。并以某大型炼化企业为实例，介绍了该企业的在实施清洁生产过程中的一些实践活动。     

中国化工和石化业近期发展现状与进展

中国化学品市场销售额现已位居世界第4，不久将超过德国而成为世界第三大化学品市场。“人世”以来，反倾销力度明显加大，化工园区建设速度正在加快，石化扩能开始走向经济规模，跨国公司全方位投资中国石化业，中国化工和石化业正在融入世界、走向世界。     

垃圾焚烧飞灰双重稳定资源化的研究

为实现垃圾焚烧飞灰的无害化和资源化，先将绿矾溶液与飞灰混合后氧化稳定飞灰中的重金属，然后将处理后的飞灰与水泥混合、养护，使焚烧飞灰在双重稳定化的同时，得到的水泥砌块浸出浓度低，具有相当的强度，可以在特殊场合安全利用。还以Pb、Cd和Cr为代表，检验双重稳定化过程中一些反应条件的选用对重金属的稳定效果，并对比了双重稳定化所获得的砌块与直接水泥固化所得砌块的强度。研究结果表明，自然淡水可为化学处理介质，洗去盐分有利于重金属固化，化学稳定化后再与水泥混合获得的砌块试件强度明显提高。     

化工专业计算机实验教学与机房管理

计算机辅助教学是实现教学现代化的重要手段。为了提高学生计算机的应用能力,为专业实验教学服 务,必须加强计算机机房的建设与管理。