膜下滴灌条件下不同灌溉量对番茄根系分布和产量的影响

采用分层挖掘法,对膜下滴灌5 426 m³·hm^-2（W1)、4 419 m³·hm^-2（W2）、3 700 m3·hm^-2（W3）3个灌溉量下番茄根系分布特征和产量进行了研究。结果表明：随灌水量的减少,番茄根系表现出向深层发展的趋势,符合“水大根小”的特征,根长、根表面积、根长密度随着土壤深度的增加均呈“单峰型”曲线：即灌水量愈少,根长、根表面积、根长密度的峰值愈位于土壤的深层;番茄根冠比也随着灌水量的减少而呈增大的趋势,W2处理、W3处理分别比W1处理提高了26.53%和70.71%;适度的控制灌溉水量可以促进根系的生长发育,扩大水分吸收空间,有利于番茄增产,4 419 m³·hm^-2灌溉量是膜下滴灌最适宜灌溉水量。     

Topographic differentiation simulation of crop yield and soil and water loss on the Loess Plateau

De-farming slope farmland has been an effective measure in recent years for the improvement of the eco-environment and the mitigation of soil and water loss on the Loess Plateau. This paper, taking the Yangou Basin as a case study and using day-by-day meteorological data of Yan’an station in 2005, simulated and analyzed the quantitative relation between crop yield, soil and water loss and topographic condition with the aid of WIN-YIELD software. Results show that: 1) topographic gradient has important influence on crop yield. The bigger gradient is, the lower the crop yield. Yields of sorghum and corn decrease by 15.44% and 14.32% respectively at 25° in comparison to the case of 0°. In addition, yields of soya, bean and potato decrease slightly by 5.26%, 4.67% and 3.84%, respectively. The influences of topographic height and slope aspect on crop yield are slight. 2) Under the same topographic condition, different crops’ runoff and soil loss show obvious disparity. Topographic gradient has important influence on soil and water loss. In general, the changing trend is that the soil and water loss aggregates with the increase of gradient, and the maximal amount occurs around 20°. The influence of topographic height is slight. Topographic aspect has a certain effect, and the fundamental characteristic is that values are higher at the aspect of south than north. 3) Topographic gradients of 5° and 15° are two important thresholds. The characteristic about soil and water loss with the variation of topographic gradients show that: the slope farmland with gradient less than 5° could remain unchanged, and the slope farmland more than 15° should be de-farmed as early as possible.     

供水管井设计出水量的确定

论述了管井出水能力的概念及确定管井出水量的理论依据。科学合理的出水量设计和避免过量抽水,是确保管井良好运行、延长管井使用寿命的关键。并以孟加拉国Barapukuria电厂水源地为例,对管井出水量的设计方法进行了详细说明。      

设施番茄产量和品质对不同浓度CO2的响应

为了明确设施番茄对CO₂的生理响应及需求规律,以“美红2号”为试验材料,测定增施600、900、1 200 mg/kg的CO₂后,番茄的开花量、单株果数、果重、含糖量、含酸量及维生素C含量。结果表明：增施CO₂可以提高番茄花量25%～50%,提高单株结果数量,增产28.29%～51.04%,但对平均果重没有影响。与对照相比,增施CO₂20 d后,600、900、1 200 mg/kg处理的果实含糖量分别为5.27、5.49、5.65 g/kg,明显高于对照4.71 g/kg的含糖量;含酸量分别为2.48、2.23、2.02 g/kg,显著低于对照区3.03 g/kg的含酸量;维生素C含量分别为356.38、420.38、348.38 mg/kg,显著高于对照区260.88 mg/kg的含量,其中900 mg/kg处理对维生素C的提升效果最好。在温室中增施CO₂不但能提高番茄产量,还能有效改善番茄品质,适宜的剂量以900 mg/kg为宜。     

RUNOFF GENERATION AND SOIL EROSION IN SMALL AGRICULTURAL CATCHMENTS WITH LOESS-DERIVED SOILS

Over a two-year period, rainfall, runoff and sediment output were measured in six small agricultural catchments (3–10 ha) in south Limburg (The Netherlands). These measurements were needed for validation of an erosion model for South Limburg (LISEM). In this paper, results of the measurements are presented and processes that determine surface runoff and sediment yield during winter and summer rainfall are identified. Before the start of the measurement programme, surface slaking and crust formation on the erodible loess soils were thought to be the main cause of overland flow and soil erosion in South Limburg. This was the starting point for soil conservation measures in the area. The measurement results discussed in this paper show that in some catchments much runoff occurred in winter and that soil moisture storage capacity may be just as important for runoff generation as infiltration capacity. Therefore, when modelling soil erosion and optimizing erosion control measures for South Limburg, runoff generation through Hortonian as well as through saturation overland flow must be considered.     

分布式侵蚀产沙模型研究进展

随着计算机技术与地理信息系统(GIS) 技术的发展, 分布式侵蚀产沙模型成为当今土壤侵 蚀领域研究重点与发展方向。本文在分析国内外几个主要的分布式侵蚀产沙模型基础上, 探讨了 分布式侵蚀产沙模型的技术路线与技术实现, 最后指出目前我国分布式侵蚀产沙模型研究存在 的主要问题: ( 1) 分布式水文模型的深入研究为分布式侵蚀产沙模型提供了不少借鉴, 但如何在 分布式水文模型的基础上开发侵蚀模块还存在一些问题; ( 2) 目前国内分布式土壤侵蚀模型大都 基于黄土高原而得出, 模型有一定的局限性; ( 3) 当前的大多侵蚀产沙的关系式( 尤其是坡面侵蚀 关系式) 是经验型的, 汇沙的过程考虑得过于简单, 没有深入探讨水文与土壤侵蚀之间的关系; ( 4) 目前大多数分布式土壤侵蚀模型没有考虑次暴雨产流的时间变化与空间变化。     

Study on Site Specific Design Earthquake Ground Motion of Nuclear Power Plants in China

The main technical backgrounds and requirements are introduced with regard to earthquake ground motion design parameters in several domestic and American standards, codes and guides involved in the seismic analysis and design activities of nuclear power plants in China. Based on the research results from site seismic safety evaluation of domestic nuclear power plant projects in the last years, characteristics and differences of site specific design spectra are analyzed in comparison with standard response spectra, and the suitability of standard response spectra for domestic nuclear power plant projects is discussed.     

管道穿越黄土陡坡斜井工程稳定性分析

长输油气管道工程频遇黄土冲沟,给管线的施工和安全运营带来了困难。基于邓肯-张非线性弹性本构模型,利用数值模拟方法,对斜井开挖法穿越边坡的井周及坡体的受力变形规律进行了系统的研究和分析。结果表明,在确保斜井布设在边坡潜在的最危险滑动面以外的前提下,坡顶斜井入口越接近坡肩,斜井井周及坡体的稳定性越好。鉴于黄土斜井拱顶易出现塌落的问题,基于多工况数值模拟分析结果,结合响应面方法,构建了拱顶屈服区深度的预测公式,经验证相关性良好,可用于对斜井穿越黄土冲沟或陡坡的支护设计。     

柔性和刚性浅基础的地基承载能力分析

为了研究刚性和柔性加载面下地基的破坏机制和极限承载力,着重对比分析了不考虑土体自重条件下柔性基础、基底完全光滑或完全粗糙的刚性基础的地基,采用关联流动的Mohr-Coulomb内切圆屈服准则,通过增量加载的有限元方法,全程模拟了地基由初始的线弹性状态逐渐过渡到塑性流动的极限破坏状态的过程。通过对这3种基础类型下地基的计算结果的对比分析,并结合国内外模型试验成果,得到如下结论：柔性和刚性浅基础地基在不考虑土体自重的条件下有相近的地基极限承载力,但基底水平面上竖向应力和位移的发展规律、临塑荷载及滑动面有着明显的区别。