科技进步的原理与农业科技进步贡献率

农业科技进步贡献率一词在国内农业科技管理活动中应用比较广泛,但从纯科技的角度认识这个概念会产生严重的误解,不切实际地使用这个词也会产生严重的偏差。文章系统阐述了科技进步的基本概念、影响因素和测定方法的发展,分析了农业科技进步的作用、模式及其机制,介绍了测定农业科技进步的基本方法。在此基础上,提出要正确理解和应用农业科技进步贡献率。     

发挥第二课堂的作用培养学生创新素质和能力

笔者通过对创新能力和创新素质内涵的各种研究观点的总结分析,初步论述了大学生第二课堂目标的核心和实质。通过对高校大学生创新素质和能力以及创新实践活动的现状分析,提出了提升大学生第二课堂主阵地效能培养学生创新素质和能力的措施。     

“绿色革命”以来大气CO2浓度升高对C3作物营养品质的影响

自20世纪60年代"绿色革命"以来,育种技术和农耕技术的发展促进了农作物产量的大幅提升,然而作物的营养品质出现下降趋势。在相似的遗传背景下,大气CO₂浓度升高会使单位体积农作物产品的营养元素含量下降,因此"绿色革命"至今,农作物产品的营养元素下降可能受大气CO₂浓度升高影响。通过植物生长箱模拟"绿色革命"初期和目前的大气CO₂浓度水平(310μmol/mol和400μmol/mol),针对主要C₃作物水稻、小麦和大豆,研究"绿色革命"以来大气CO₂浓度升高对其籽粒的C、N、Fe、Zn元素含量的影响,结果表明:CO₂浓度升高对3种作物籽粒的C元素含量几乎没有影响,变化幅度在±1.5%之间;籽粒的N、Fe、Zn元素含量普遍呈现下降趋势,但均未达到显著水平。     

盐酸羟胺促进分级Fenton氧化土壤长链原油的试验研究

H₂O₂分次投加可以提高石油烃(total petroleum hydrocarbons,TPH)去除率,本试验选用900 mmol/L H₂O₂分3次投加的方式进行分级Fenton氧化修复长链原油污染土壤。在Fe²⁺、固相铁、Fe²⁺+盐酸羟胺、固相铁+盐酸羟胺4种催化体系下进行试验,发现在向Fe²⁺体系和固相铁体系加入盐酸羟胺后,后两级反应·OH强度明显增强,是未加入盐酸羟胺体系下的3倍～4倍,TPH及长链烃氧化量也大幅提高。采用向Fenton体系中加入盐酸羟胺的方式,克服了分级Fenton氧化过程中由于Fe²⁺不足导致·OH强度较第一级显著降低、TPH及长链烃氧化量大幅下降的缺陷,促进了后两级反应过程中·OH的产生,从而大大提高了后两级TPH及长链烃的去除效果,使后两级去除效果与第一级接近,能够维持在较高水平,为急需短时间进行的土壤修复提供了一定的理论依据。     

Priority setting in research for sustainable land use: the case of the Adja Plateau,Benin

TheProjet Recherche Appliquée en Milieu Réel is situated on the Adja Plateau, Southwest Benin. The project is responsible for a FSR&D programme that aims at sustainable use of the so-calledTerres de barre. Technologies tested in this context include seasonal fallowing, usingMucuna pruriens cv. group Utilis (weed control, green manure), planted fallows using fast-growing species such asAcacia auriculiformis and hedgerow intercropping systems (various woody auxiliary species). In this paper the local farming system is analyzed to identify key parameters that determine the possibilities for technology adoption. Parameters include: function and history of fields; tenureship; the field's position with regard to fertility flows in the farming system.The paper also aims at understanding the reasons behind low crop yields, in this case maize. An analysis of the soil's chemical fertility, using a computer-based fertility assessment model and data from literature, shows some anomalies with respect to the availability of nutrients from organic matter. Data presented on the use of green manures and oil palm fallow compared to cultivated fields make it likely that organic matter management is a crucial factor in sustainable use of these soils (maintenance of soil structure and soil life). Given key parameters, a matrix is used to determine potential niches in the farming system for the various biomass production technologies mentioned previously, including the locally developed planted fallow based on oil palm.     

Effect of the time of application of nitrogen fertilizer on the total NPK content of young apple trees

Abstract

Ammonium nitrate fertilizer, whether applied in spring, summer or autumn, resulted in a rapid increase in the total N content of most tree tissues, although autumn‐applied N remained mainly in the tree roots through the winter. The total P content of the trees was increased by added N fertilizer but the total K content was decreased. Analysis showed that significantly more N was lost in the leaves abscissing from the spring and summer‐N trees than from the autumn‐N trees or controls; also more P was lost from trees given spring N.     

本溪县兴林农民专业合作联社发展经验探讨

以本溪县兴林农民专业合作联社为例,介绍联社的筹建、组织机构、基本情况及发展规划,探讨联社在扶持合作社发展、解决单一合作社普通存在的困难、增强合作社特色产业研发能力、推进特色产业发展方面取得的明显经济效益和社会效益,为联社的组建及发展提供理论参考。     

Nitrite production by Nitrosomonas europaea and Nitrosospira sp. AV in soils at different solution concentrations of ammonium

Although it remains unclear why NH₃-oxidizing bacteria (AOB) of the genus Nitrosospira dominate soil environments, and why Nitrosomonas spp. are less common, virtually no studies have compared their behavior in soil. In this study, the NH₃ oxidation rates of Nitrosomonas europaea (ATCC 19718) and Nitrosospira sp. AV were compared in three differently textured soils containing a range of extractable contents (2-11 μg soil). Soils were adjusted to pH 7.0-7.4 with CaCO₃ and sterilized with γ-radiation. Cell suspensions of each bacterium were inoculated into the soils to bring them to two-third of water-holding capacity and cell densities ∼2.5×10⁶ g^−1 soil. In virtually all cases, rates of production for both N. europaea and Nitrosospira sp. AV were linear over 48 h, and represented between 13 and 75%, respectively, of the maximum rates achieved in soil-free bacterial suspensions. Soil solution concentrations that supported these rates ranged between 0.2 and 1.5 mM. Addition of 21-36 μg soil raised soil solution levels to 1.8-2.5 mM and stimulated production to a greater extent in N. europaea (3.3-6.6-fold) than in Nitrosospira sp. AV (1-2.1-fold). Maximum rates of production were obtained by raising soil solution levels to 3-4 mM with a supplement of ∼80-90 μg soil. K_s values in soil for Nitrosospira sp. AV and N. europaea were estimated as 0.14 and 1.9 mM , respectively, and estimates of V_max were about 3.5-times higher for N. europaea (0.007 pmol h^−1 cell^−1) than for Nitrosospira sp. AV (0.002 pmol h^−1 cell^−1). The cell density of N. europaea increased in sterile Steiwer soil independent of supplemental . In the case of treatments receiving supplemental , growth yields of N. europaea calculated from either produced or consumed were similar to those reported in literature (3.5×10⁶-6×10⁶ cells μmol^−1). A higher growth yield was measured in the case of zero added (2.7×10⁷ cells μmol^−1), indicating that use of organic carbon compounds might have occurred and resulted in some energy sparing. Our results suggest that Nitrosospira spp. with a K_s similar to Nitrosospira sp. AV may have an advantage for survival in soil environments where soil solution levels are less than 1 mM. However, it is apparent that AOB like N. europaea are poised to take advantages of modest increases in extractable that raise soil solution levels to about 2.0-2.5 mM.     

The other side of the coin: A case study on the impact of financial autonomy on irrigation management performance in the Philippines

The paper assesses the impact of the removal of operating subsidies to the Philippine National Irrigation Administration on the management performance of a small canal irrigation system in Southern Luzon. It shows that in this case the creation of financial autonomy of the agency did not fully engender the often assumed positive effects regarding both accountability relationships and irrigation management performance. The conclusions specify a number of issues related to the theory of financial autonomy which require further study.     

Operation and maintenance in Asian irrigation: Reappraising government and farmer responsibilities and rights

A major policy concern in irrigation development is reducing government costs of both construction and operation and maintenance. There is increasing interest in shifting some of these costs to the farmers using the irrigation facilities. This paper discusses the opportunities for reducing certain direct costs to government by collaborative arrangements with water users so that the latter mobilize more of their own resources to implement specified O&M activities. Five propositions are discussed which suggest the prerequisites for successful collaboration: (1) reexamining the processes of design and construction now being used, (2) reorienting the policies and procedures of the irrigation agency, (3) increasing farmer involvement in operations, (4) increasing local organizational capacity, and (5) creating new financial procedures.