Column Holdup Formula of Soil Solute Transport

The shortcomings of the present two formulae for describing column holdup are analyzed and deductions are made to find a new formula. The column holdup, Hw, described by the new formula is dimensional,and related to soil solute transport kinesis and column physical properties. Compared with the other two column holdups, Hw is feasible to describe dimensional column holdup during solute transport process. The relationships between Hw and retardation factor, R, in different solute transport boundary conditions are established.     

控制土壤含水量对蔬菜产量及露地菜田水分渗漏量的影响

【目的】通过揭示不同土壤含水量对蔬菜产量及蔬菜地土壤水分渗漏量的影响,为蔬菜生产中合理灌溉提供指导。【方法】通过3年田间试验,利用TDR连续监测土壤含水量,运用田间定位通量法计算土体水分渗漏量,分析不同水分处理下蔬菜产量和土体水分渗漏量之间的差异。【结果】传统水分处理下蔬菜地水分累积渗漏量为982mm,其中蔬菜生长期内累积渗漏量为748mm,占蔬菜生长期内供水量的36%;优化水分处理和充分水分处理下蔬菜地水分累积渗漏量230mm和468mm,其中蔬菜生长期内水分累积渗漏量分别144mm和293mm,占各处理下供水量的9%和17%。除2002年优化和充分水分处理下花椰菜产量高于传统水分处理下花椰菜产量并达到显著水平外,其余年份蔬菜产量并无显著差异。【结论】保持土壤含水量在蔬菜生长有效土壤含水量50%～80%的优化水分处理在蔬菜生产中有很大的推广价值。     

Responses of Lowland,Upland and Aerobic Rice Genotypes to Water Limitation During Different Phases

Rice yield reduction due to water limitation depends on its severity and duration and on the phenological stage of its occurrence. We exposed three contrasting rice genotypes, IR64, UPLRi7 and Apo (adapted to lowland, upland and aerobic conditions, respectively), to three water regimes (puddle, 100% and 60% field capacity) in pots during the vegetative (GSI), flowering (GSII) and grain filling (GSIII) stages. Stress at all the three stages significantly reduced yield especially in lowland genotype IR64. Effect of water limitation was more severe at GSII than at the other two stages. Stress at GSI stage reduced both source activity (leaf area and photosynthetic rate) and sink capacity (tiller number or panicle number per pot). When stress was imposed at GSII, spikelet fertility was most affected in all the three genotypes. In both GSII and GSIII, although leaf area was constant in all the three water regimes, estimated relative whole-plant photosynthesis was strongly associated with yield reduction. Reduced photosynthesis due to stress at any given stage was found to have direct impact on yield. Compared to the other genotypes, Apo had deeper roots and maintained a better water relation, thus, higher carbon gain and spikelet viability, and ultimately, higher biomass and productivity under water-limited conditions. Therefore, screening for these stage-dependent adaptive mechanisms is crucial in breeding for sustained rice production under water limitation.     

排沙漏斗中的二次流及其影响

根据理论分析和现有试验成果相结合的方法,研究了排沙漏斗中二次流在排沙中的重要作用。应用二次流理论解释了一些排沙漏斗结构设计的内在原因,从二次流的角度去说明排沙漏斗是如何实现高效排沙的,得到了一些被试验和实践证实了的结论。着重地阐述了排沙漏斗在处理以悬移质为主的泥沙和以推移质为主的泥沙时排沙漏斗直径大小调整的原因。提出了平衡悬移质所需的水流临界径向速度公式,它为定量地判断水流能否向中心输移悬移质颗粒提供参考。     

鄱阳湖水位特征与湿地生态保护

从分析江湖关系入手，研究鄱阳湖的水位及湿地生态特征，并提出人工控湖等加强湿地生态保护的对策建议。     

施用磷肥对环境的影响探讨

磷肥的施用与环境质量密切相关。本文讨论了过量施用磷肥加剧了农业非点源污染,农业非点源磷的累积增加了水体富营养化的风险,同时,磷肥中的重金属随磷肥的施用进入土壤环境,对土壤环境质量和农产品品质以及人体健康也有一定的影响。     

Effect of aggregate size and soil water content on emergence of soybean (Glycine max, L. Merr.) and maize (Zea mays, L.)

Rapid wetting of irrigated soils often leads to slaking and slumping, and on drying a surface crust and hard-set conditions may occur. This results in reduced crop emergence unless the surface is kept moist. The effect of aggregate size and water content on the emergence of soybean and maize from an Entic chromustert (heavy cracking clay) was determined using pots of sieved aggregates with size ranges less than 1, 1–2, 2–5 and 5–15 mm at soil water contents of 15, 20 and 25 g (100 g)⁻¹. Unsieved soil was used as a control. Greatest emergence tended to occur from fine (1–2 mm) seedbeds compared with coarse (5–15 mm) seedbeds for both crops. A covered treatment, simulating a stubble mulch, resulted in greater emergence than an uncovered treatment for all water contents and aggregate sizes. Earlier emergence occurred from finer (less than 1 mm and 1–2 mm) seedbeds than from coarse (5–15 mm) seedbeds, and at the greatest water content used. Soil strength, measured with a shear vane, decreased with increasing water content and tended to be less on fine (1–2 mm) seedbeds compared with very fine (less than 1 mm) or coarse (5–15 mm) seedbeds. It is recommended that, for good emergence from this Entic chromustert, seedbeds be brought to a water content of 25 g (100 g)⁻¹ by capillary wetting to prevent hardsetting and consist of 1–2 or 2–5 mm aggregates for soybean and maize, respectively, and have a stubble mulch on the surface. This corresponds to an equivalent depth of water of 15 mm and 9 mm for soybean and maize, respectively, in the top 50 mm of the profile.     

河北二季作区马铃薯节水灌溉研究初报

为研究河北二季作区马铃薯整个生育期不同灌水量对其生长发育的影响,以该地主栽品种为材料,根据不同生育期需水规律,设定5个不同水量梯度的滴灌处理和1个常规沟灌处理(CK);调查分析了不同处理间物候期、重要农艺性状、病害发生情况和产量等相关指标。结果表明,处理3(采用滴灌模式,水量为110 m3)与常规沟灌相比,马铃薯生长势、总产量和商品薯产量无显著差异,生育期提前,病害较轻,商品薯率提高7.2%,节水35.41%,综合表现优于其他处理,为试验地区最佳灌水量。     

新世纪首都水源区发展战略研究报告

作为首都郊区的密云县 ,应该自觉找准本县在首都经济中的战略地位 ,找到一条持续快速健康发展的道路。新世纪首都水源区的发展战略应该是 :着眼首都未来发展对水源和环境的高标准要求 ,切实履行高质量保护水源和环境的特殊职责 ;走环境立县、引进强县、科教兴县和依法治县之路 ;努力建设清洁优美的自然环境、先进完善的设施环境、高效规范的体制环境和健康和谐的人文环境 ;构建以高新技术工业、绿色农业、生态旅游业和环保节能型建筑建材房地产业为支柱的首都水源区经济体系 ;突出县工业开发区、密云卫星城与中心镇建设、旅游西线开发和畜牧业产业化四个战略重点 ,促进经济持续快速健康发展 ,实现强县富民的目标。     

磁处理水添食对家蚕若干数量性状影响的初步试验

研究了用不同强度磁处理水添食对家蚕生长及若干数量性状影响的生物效应。结果表明 ,从 3龄起连续添食磁处理水后与对照区比较 ,蚕体增长率提高 ,健康性和生命力有所增强 ,龄期经过缩短 1～ 2d ,茧质调查表明 ,全茧量、茧层量、茧层率等性状也都不同程度表现了正向效应 ,其中以场强为 2 0 0～ 30 0mT的磁处理水添食 ,作用效果较为显著