不同生育期干旱对冬小麦产量及水分利用效率的影响

用盆栽对冬小麦不同生育阶段进行不同程度水分调亏试验结果表明 :拔节—孕穗期、抽穗—扬花期和灌浆—成熟 3个阶段内 RW上限为 4 0 %、5 0 %、60 %的水分亏缺均引起了产量的极显著下降 ,而且水分亏缺越严重 ,产量降低越大。在 3个生育阶段内进行 RW上限为 4 0 %的水分调亏减产幅度都很大 ,而且 3个生育阶段之间差异不明显 ;进行 5 0 %、60 %水分调亏 ,其减产程度则与生育期有关。灌浆—成熟期的减产程度大于前二个时期 ,这可能与前二个阶段复水后作物的补偿生长有关。不同生育期水分亏缺对冬小麦产量构成因素的影响也不同 ,拔节—扬花期水分亏缺主要减少了穗粒数 ,灌浆—成熟阶段的水分亏缺主要减少了千粒重     

基于多周期同步测量的涡轮式流量测试研究

涡轮流量计是泵试验中常用的流量测试仪表之一。文章在讨论涡轮流量计的结构和基本原理的基础上,分析了“测频法”和“测周法”流量测试方法存在的精度不等的问题,提出了多周期同步测量技术在涡轮式流量测试中的应用,从而进一步提高了流量测试精度。     

罗湾水电站引水系统过渡过程研究

为了对罗湾水电站增容前后的引水系统过渡过程和机组增容改造对引水系统建筑物的影响进行研究，应用水击计算方法中的电算法进行计算，得出了调压室最低、最高涌浪水位，蜗壳处最大压力水头和机组转速最大升高。结果表明，电站增容后引水系统完全能满足有关规范和设计的要求。     

Managing secondary dryland salinity: Options and challenges

Salt occurs naturally at high levels in the subsoils of most Australian agricultural land. As a result of clearing native vegetation, groundwater tables have risen, mobilising the stored salt and causing adverse impacts on farmland, infrastructure, water resources, and biodiversity. The main action required to prevent groundwater tables from rising is establishment of perennial plants, either herbaceous (pastures or crops) or woody (trees and shrubs). Recent technical and economic research has emphasised how difficult it will be to establish sufficient perennials to get control of groundwater tables. Where watertables are already shallow, the options for farmers are salt-tolerant plants (e.g. saltbush for grazing) or engineering (e.g. deep open drains). The existing options for farm-level salinity management are reviewed, with mixed but somewhat disappointing findings regarding their suitability for addressing salinity. However, there are also a number of good prospects for development of new and better options for plant-based management of salinity, and these are described.     

Irrigation and food security in the 21st century

Global food projections indicate that food prices in the next threedecades will likely be stable or decline, but progress inreducing malnutrition in developing countries will be slow. Smallshortfalls in crop productivity growth would lead to rising foodprices and worsening malnutrition. Increased food production fromirrigation is essential, and will require expansion of irrigatedarea and water supplies, and improved efficiency of use of existingwater supplies. Neither of these growth factors will prove easy, andboth will require complex institutional and policy reforms. Failureto meet food production needs through efficient expansion andintensification of irrigated agriculture would increase pressure onland resources and hasten the process of environmental degradation.Irrigation and water development strategies have been hampered bya lack of understanding of the links between water scarcity, foodproduction, food security, and environmental sustainability.Research to improve this understanding would have high payoffs.     

灌溉渠系水利用系数的分析与计算

灌溉渠系的布置形式一般可分为串联渠系、等效并联渠系和非等效并联渠系 ,对这 3种灌溉渠系水利用系数进行了理论研究。用实例验证了上述的理论分析。研究成果可应用于实际灌溉工程     

Intensification or extensification? Factors affecting technology use in peri-urban lowlands along an agro-ecological gradient in West Africa

The paper analyses whether the increased use of lowlands in proximity to urban centres in West Africa is associated with technological intensification or extensification. Technologies are typified in terms of their orientation – land or labour saving – and market dependence for their procurement and reviews the factors driving and modifying their use in lowlands. The factors associated with technology use are analyzed empirically using geo-referenced lowland data around four urban centers along an ecological gradient in Côte d’Ivoire and Mali. The technologies analyzed include both external inputs (fertilizer, pesticide, herbicide, improved varieties) and crop management practices (plot level bunding, rice transplanting and rice direct seeding). Results from binomial logit models highlight the prominent positive and non-linear role of proximity to urban markets for the technological intensification of lowlands – an issue associated with factor scarcities and the transaction costs for procurement and marketing. Technology use in lowlands is also associated with the agro-ecological gradient, lowland development and non-native lowland users. A common thread linking these variables is that they modify resource scarcity and therefore intensification incentives. Lowlands are not always as valuable as they may seem and there may be limited incentives to intensify. Instances of significant lowland cultivation and intensification in the study sites tend to be associated with specific opportunities – driven by market opportunities and modified by seasonal, institutional or development-induced relative land scarcity. Market access is therefore a necessary but not sufficient factor for the technological intensification of lowland use. There is a need for better targeting of development efforts in terms of enabling lowland intensification or extensification as appropriate.     

Evaluation of the RZWQM-CERES-Maize hybrid model for maize production

The root zone water quality model (RZWQM) was developed primarily for water quality research with a generic plant growth module primarily serving as a sink for plant nitrogen and water uptake. In this study, we coupled the CERES-Maize Version 3.5 crop growth model with RZWQM to provide RZWQM users with the option for selecting a more comprehensive plant growth model. In the hybrid model, RZWQM supplied CERES with daily soil water and nitrogen contents, soil temperature, and potential evapotranspiration, in addition to daily weather data. CERES-Maize supplied RZWQM with daily water and nitrogen uptake, and other plant growth variables (e.g., root distribution and leaf area index). The RZWQM-CERES hybrid model was evaluated with two well-documented experimental datasets distributed with DSSAT (Decision Support System for Agrotechnology Transfer) Version 3.5, which had various nitrogen and irrigation treatments. Simulation results were compared to the original DSSAT-CERES-Maize model. Both models used the same plant cultivar coefficients and the same soil parameters as distributed with DSSAT Version 3.5. The hybrid model provided similar maize prediction in terms of yield, biomass and leaf area index, as the DSSAT-CERES model when the same soil and crop parameters were used. No overall differences were found between the two models based on the paired t test, suggesting successful coupling of the two models. The hybrid model offers RZWQM users access to a rigorous new plant growth model and provides CERES-Maize users with a tool to address soil and water quality issues under different cropping systems.     

梳穗收获飞溅损失的分析和试验

梳穗收获时梳穗齿和穗头的梳脱位置对梳穗收获机的性能影响较大．本文对梳穗收获的飞溅损失进行了初步分析与探讨．确定降低飞溅损失的最佳梳脱区和有效梳脱区并进行了试验，找出了影响飞溅损失的主要参数。     

支持向量机在水质评价中的应用

介绍了支持向量机算法的原理，建立了基于支持向量机的水质评价多层次分类检测模型，通过提取水质评价标准中的物质成分为特征参数，利用几个SVM分类器的串联组合，实现对水质的分类和识别，同时，引入类权重因子，解决训练样本类别数量不平衡而导致的错分问题，实验结果显示该方法提高了水质评价的准确性和效率。