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土壤的给水度和自由空隙率 总被引：2，自引：0，他引：2
土壤的给水度和自由孔隙率是排水设计、地下水非稳定流计算、地下水资源评价和动态预测预报的重要参数,本文分析了给水度和自由孔隙率的不同含义,区分了完全给水度(最终给水度),瞬时给水度和平均给水度的几种概念。探讨了影响给水度的主要因素和确定方法。完全给水度等于释水水分特征曲线与饱和含水率的差值,因此其数值随地下水埋深加大而增大。在同一地下水降深时,地下水下降速度愈大,瞬时给水度愈小;当地下水位下降时间相同时,地下水位降速愈大,给水度愈大。瞬时给水度随蒸发强度的增大而增大。在水位变化速度相同时,土壤的自由空隙率大于给水度。 相似文献
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《中国农村水利水电》2016,(9)
为解决双环入渗仪只能测定原状土的渗透速度,而无法测定原状土入渗湿润锋的运移规律和入渗过程中不同高度的土壤水分含量等问题,提出了一种基于频域反射法土壤水分传感器测量原状土入渗湿润锋运移规律和不同高度土壤水分含量的方法,采用arduino mega 2560单片机开发板采集土壤水分传感器检测得到的数值,设计了圆盘式底座的原状土入渗性能检测装置,土壤水分传感器安装在检测装置上,arduino mega 2560单片机开发板能够根据检测得到的数据判定原状土入渗湿润锋的运移的位置,并根据控制策略驱动检测装置,使土壤水分传感器进入下一位置进行检测,也能够对原状土入渗过程中不同位置的土壤水分含量进行连续检测。为研究原状土的入渗过程中湿润锋的运移规律和水分迁移提供参考。 相似文献
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原状土和分散土吸附试验表明,相同条件下,前者的吸附量比后者小。原状土柱弥散试验结果说明用分散土的吸附公式,计算的浓度值偏小于实测值。从数学、物理概念出发,导出了土壤等温吸附平衡公式,克服了原有公式的局限性,用其拟合国内外几个吸附和解吸试验资料,结果是满意的。 相似文献
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农田大孔隙对土壤水运动和溶质运移的影响研究 总被引：2，自引：0，他引：2
通过农场原状土和回填土试验地块比较试验，研究了天然土壤中的大孔隙对水分和溶质在土壤中迁移的影响。运用水分及污染物耦合数值计算模型，分别模拟计算了水分及保守性污染物质在原状土和回填上中的迁移规律，模型参数反映二试验地块不同土壤结构特征，数值计算成果得到了试验资料的验证。 相似文献
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为掌握机插水稻不同育秧基质配方应用效果,以二合土为营养土对照,比较研究了3个品牌基质及其与干细土、壮秧剂混拌的不同配方基质育秧应用试验效果。结果表明,不同配方基质育秧与营养土对照相比,明显提高秧苗素质,产量结构合理,增产效果极显著。尤其是育苗基质3+二合土+壮秧剂配方增产效果最优。 相似文献
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连山区花生施肥指标体系研究 总被引：1，自引：0，他引：1
通过进行"3414"田间试验,初步建立葫芦岛市连山区花生测土配方施肥指标体系,对施肥配方及产量数据进行一元二次回归分析,得出最高产量和最佳经济条件下的推荐施肥量,为连山区花生的合理施肥提供科学依据。 相似文献
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为验证配方施肥效果，以玉米为原料，2006年在铁岭地区进行配方施肥肥效试验。试验结果表明：施用玉米配方肥能促进玉米的成长发育、提高植株的株高、减少秃尖长度、增加穗粒数和千粒质量；与常规施肥相比，玉米配方施肥有较好的增产效果．3个试验点的增产率分别为3．06％、13．43％和5．60％。经济效益分析表明，施用玉米配方肥可增收节支，适宜在铁岭地区推广应用。 相似文献
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Crop models are useful tools for integrating knowledge of biophysical processes governing the plant-soil-atmosphere system. But few of them are easily usable for water and yield management especially under specific cropping systems such as direct seeding. Direct seeding into mulch (DSM) is an alternative for conventional tillage (CT). DSM modifies soil properties and creates a different microclimate from CT. So that, we should consequently consider these new conditions to develop or to adapt models. The aim of this study was to calibrate and validate the PILOTE [Mailhol, J.C., Olufayo, A.A., Ruelle, P., 1997. Sorghum and sunflower evapotranspiration and yield from simulated leaf area index. Agric. Water Manag. 35, 167-182; Mailhol, J.C., Zaïri A., Slatni A., Ben Nouma, B., El Amami, H., 2004. Analysis of irrigation systems and irrigation strategies for durum wheat in Tunisia. Agric. Water Manag. 70, 19-37], an operative crop model based on the leaf area index (LAI) simulation, for corn and durum wheat in both DSM and CT systems in Mediterranean climate. In DSM case, simple model modifications were proposed. This modified PILOTE version accounts for mulch and its impact on soil evaporation. In addition root progression was modified to account for lower soil temperatures in DSM for winter crops. PILOTE was calibrated and validated against field data collected from a 7-year trial at the experimental station of Lavalette (SE of France). Results indicated that PILOTE satisfactorily simulates LAI, soil water reserve (SWR), grain yield, and dry matter yield in both systems. The minimum coefficient of efficiency for SWR was 0.90. This new version of PILOTE can thus be used to manage water and yield under CT and DSM systems in Mediterranean climate. 相似文献
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为了实现黄土高原地区滴灌条件下枣树园土壤含水率的小范围快捷监测,根据FAO-56水分胁迫系数的定义和相关计算公式,得到了基于土壤水分胁迫系数的黄土高原地区滴灌条件下枣树根层土壤平均含水率估算公式．2009年4-9月将该公式应用于西北农林科技大学陕西米脂孟岔试验站的枣树试验园,配置了3种不同的土壤含水率控制下限,对枣树2个重要生育期的土壤含水率进行了估算,模拟了水分动态变化过程,并对估算值和实测值进行对比和误差分析．结果表明:采用基于FAO-56水分胁迫系数的计算公式对土壤含水率的动态模拟达到了较高的精度,估算值与实测值之间误差较小:其中开花坐果期各处理(灌水下限为60％,50％,40％的田间持水率)的估算值与实测值之间的相关系数分别为0828 0,0907 3,0935 1;标准误差分别为0055,0093,0068．果实膨大期各处理的相关系数分别为0777 2,0766 7,0905 5;标准误差分别为0057,0092,0079．估算值与实测值之间的相关系数随土壤含水率的增大而减小,随土壤水分胁迫程度的增大而增大,即土壤含水率较高时对公式精度有一定的影响．该方法较适用于黄土高原半干旱地区,对农业用水管理具有一定参考价值． 相似文献
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Retrieving Soil Moisture Storage in the Unsaturated Zone Using Satellite Imagery and Bi-Annual Phreatic Surface Fluctuations 总被引：1，自引：0，他引：1
Ongoing research into net groundwateruse in Pakistan needed soil moisturestorage information to compute monthlysoil water balances. A methodology isdeveloped to retrieve soil moisture storagein the complete unsaturated zone from rootzone soil moisture content (based onthermal satellite imagery) and bi-annualphreatic surface fluctuations. A root meansquare error in volumetric soil moisturecontent of 0.05 cm3 cm-3 in theroot zone of irrigated fields was found forthe case study in Pakistan. A new simpleparameterisation of matric pressure headdistribution between the root zone and thephreatic surface was developed. Theabsolute root mean square error in dailyestimates of unsaturated zone storage forshallow (2 m) and deep groundwater tables(10 m) was found to be 7 cm (the averagetotal storage is 110 cm). It is concludedthat the spatial variation of the soilmoisture storage depends on the depth ofthe phreatic surface, whereas the temporalvariation is mainly controlled by the rootzone soil moisture changes. The resultsshow that for an area of 3 million ha, storagechanges of ± 10 cm month-1 occur,which is a significant quantity for monthlywater balance analysis. Conventionalmethods such as specific yield do notconsider moisture changes in the irrigatedtop soil when the groundwater table isdeep. The new method is, therefore, apossible alternative solution, especiallyin areas where hydrological data isscanty. 相似文献
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Wetted soil volume as a design objective in trickle irrigation 总被引：1，自引：0，他引：1
B. Zur 《Irrigation Science》1996,16(3):101-105
The restricted volume of wetted soil under trickle irrigation and the depth-width dimensions of this volume are of considerable practical importance. The volume of the wetted soil represents the amount of soil water stored in the root zone, its depth dimension should coincide with the depth of the root system while its width dimension should be related to the spacing between emitters and lines. Thus, the volume and geometry of the wetted soil under an emitter should become an objective rather than an end result of the design process. The purpose of this paper is to introduce and demonstrate an inverse design process, where a management-controlled wetted soil volume, Vm, is estimated first. The parameters which influence the value of Vm are the available water holding capacity of the soil and the peak daily crop water use representing specific field conditions. The irrigation interval and the management-allowed deficit are additional parameters which affect the wetted volume and could be changed depending on crop sensitivity as well as water and irrigation equipment accessibility. A truncated ellipsoid is assumed to best represent the geometry of the wetted soil volume under an emitter. Pairs of possible depth-width dimensions which satisfy the estimated volume of the wetted soil are then computed using the equation of a truncated ellipsoid. Finally, depth-width-discharge combinations which can yield the estimated wetted soil volume are computed using an equation proposed by Schwartzman and Zur (1986). The most suitable combination based on local irrigation practices and available emitters is then selected. Computational examples for three soil types under the same climatic conditions are presented and discussed. 相似文献
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Potential benefits of early vigor and changes in phenology in wheat to adapt to warmer and drier climates 总被引：1，自引：0，他引：1
Developing crop cultivars with novel traits could help agriculture adapt to climate change. As introducing new traits into crops is expensive and time consuming, it is helpful to develop methods which can test whether a potential new plant trait increases or maintains production in future climates. We used a crop-soil simulation model (APSIM-Nwheat) to test whether changes in physiological traits, related to early vigor and flowering time, would result in increased yield when compared to traditional cultivars of wheat grown at higher temperatures, elevated atmospheric CO2 and lower rainfall in a Mediterranean climate. Early vigor was simulated by changing four different plant traits. The impact of each trait on grain yield varied with climate scenario and soil type. Higher specific leaf area had minimal effect on yield for the historical climate, but it could increase production in future warmer climates. Increased rooting depth generally had a positive impact on yield, while lower radiation use efficiency and earlier flowering tended to reduce yield. The interaction between these traits was generally positive, and our results indicate that early vigor may improve yield for a range of future climate scenarios. However, in the low rainfall regions, early vigor is unlikely to compensate for rainfall reductions of ?30%. Yield gains for early vigor are likely to be larger on sandy loam than on heavier clay soil.The simulation of cultivars differing in flowering time showed that in drier climates earlier flowering cultivars increase potential yield while in warming climates later cultivars increase yield.In conclusion, our analyses suggest that there is great potential for adapting wheat systems to climate change by introducing cultivars with new traits. Our results also show how simulation analyses can assist plant breeders in determining which traits could be important for crop production in future climates. 相似文献