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1.
Moisture content and bulk density largely characterize physical and mechanical soil status and behaviour. A nondestructive determination of these soil properties is essential. Time domain reflectometry (TDR), although widely accepted for determination of volumetric water content, θ, has its limitations, and recently a frequency domain (FD) sensor has been developed and tested. An equation relating relative permittivity, ?′, to gravimetric water content, w, and bulk density, p, was established for three soil types (sand, sandy loam and clay). If ?′ and w are known, our model can be used to calculate bulk density and associated volumetric water content, θ, keeping in mind that θ= pw. Utilization is found in long-term monitoring of moisture fluctuations or short-term detection of traffic-induced soil compaction. 相似文献
2.
A new coaxial line cell for the determination of dielectric spectra of undisturbed soil samples was developed based on a 1.625‐inch ‐ 50 Ω coaxial system. Undisturbed soil samples were collected from a soil profile of the Taunus region (Germany) and capillary saturated followed by a step‐by‐step de‐watering in a pressure plate apparatus as well as oven‐drying at 40°C. The resultant water contents of the soil samples varied from saturation to air‐dry. Permittivity measurements were performed within a frequency range from 1 MHz to 10 GHz with a vector network analyser technique. Complex effective relative permittivity or electrical conductivity was obtained by combining quasi‐analytical and numerical inversion algorithms as well as the parameterizing of measured full set S‐parameters simultaneously under consideration of a generalized fractional dielectric relaxation model (GDR). The measurement of standard materials shows that the technique provides reliable dielectric spectra up to a restricted upper frequency of 5 GHz. For the soil samples investigated, the real part of complex effective relative permittivity ?′r,eff and the real part of complex effective electrical conductivity σ′eff decreased with increasing matric potential or decreasing water contents. Soil texture and porosity affect the dielectric behaviour at frequencies below 1 GHz. For frequencies above 1 GHz minor texture effects were found. The presence of organic matter decreases ?′r,eff and σ′eff. At 1 GHz, the empirical model of Topp et al. (1980) is in close agreement with the experimentally determined real part of the effective permittivity with RMSEs ranging from 1.21 for the basal periglacial slope deposit and 1.29 for bedrock to 3.93 for the upper periglacial slope deposit (Ah). The comparison of the experimental results with a semi‐empirical dielectric mixing model shows that data, especially for the organic‐free soils, tend to be under‐estimated below 1 GHz. The main advantage of the new method compared with conventional impedance and coaxial methods is the preservation of the natural in‐situ structure and properties such as bulk density of the investigated soil samples. 相似文献
3.
基于介电特性与SPA-SVR算法的水稻含水率检测方法 总被引：2，自引：2，他引：0
为提高基于介电法水稻含水率的检测精度,以北粳3号水稻为研究对象,利用阻抗分析仪及自制同轴圆柱型电容器测量了不同含水率水稻在1 kHz～1 MHz频率下的相对介电常数ε′及介质损耗因数ε"。采用x-y共生距离法划分了72个样本校正集和48个样本预测集。利用无信息变量消除法及连续投影法选取介电参数(ε′、ε"及ε′和ε"两者结合)的特征变量,分别利用所提取的特征变量以及单频、全频下的介电参数来建立预测水稻含水率的多元线性回归及支持向量机回归模型,分析模型的预测性能,并对最佳模型的含水率预测结果进行温度补偿。结果表明:基于ε′与ε"两者结合并利用连续投影法提取特征变量建立的支持向量机回归模型预测效果最佳,其预测集决定系数为0.980,预测均方根误差为0.403%。最佳预测模型对不同品种水稻的含水率预测值与烘干法测得的含水率实测值的绝对误差集中分布在±0.5%内,该研究可为粮食含水率的检测提供参考。 相似文献
5.
东北黑土区农业机械化水平高,农机作业压实导致的土壤结构和物理性状退化问题日益严重,压缩特性是定量分析土壤压实过程的有效手段,但目前黑土压缩特性随初始含水量和初始容重的变化规律尚不明确。为了解初始含水量和初始容重对黑土压缩特性的影响程度及其变化关系,该研究以重塑黑土为对象,设0.15、0.20、0.25、0.30、0.35、0.40 g/g共6个初始含水量水平,设1.00、1.10、1.20、1.30、1.45、1.60 g/cm3共6个初始容重水平,使用固结仪进行单轴压缩试验测定土壤压缩曲线,分析初始含水量和容重对压缩特性影响。结果表明,土壤初始含水量、容重及两者交互作用均极显著影响重塑黑土压缩特性(P<0.001),据此建立了预测压缩特性的土壤传递函数。黑土的预固结压力为10.42～1 106.17 kPa,与初始含水量显著线性正相关、与初始容重显著线性负相关(P<0.05);压缩指数为0.311～0.852,与初始含水量和容重呈二元多项式方程的关系,随初始容重的增大而降低,在中等含水量时最大;回弹指数为0.007～0.321,与初始含水量正相关,与... 相似文献
6.
干旱区盐渍土介电常数特性研究与模型验证 总被引：2，自引：3，他引：2
常用的土壤介电模型一般都是针对非盐渍化土壤提出来的,对于干旱区盐渍化土壤,模型对于介电常数虚部的描述与实际测量情况有一定差距。为了更好地深入研究干旱区盐渍化土壤介电常数特性,该文选择盐渍土介电模型(修正的含水含盐土壤Dobson介电模型)作为典型研究区盐渍化土壤介电常数的基础模型,模拟分析土壤介电常数对模型参数的响应,在野外实测数据的支持下验证了盐渍土介电模型的适用性。研究结果表明:1)在低频区域(0.5相似文献
7.
基于介电特性与IRIV-GWO-SVR算法的番茄叶片含水率检测 总被引：10，自引：8，他引：2
为了探究利用介电特性检测作物水分状况的可行性,研究了一种基于介电特性的有效、快速、精确检测番茄叶片含水率的方法。以300片不同含水率的番茄叶片为研究对象,通过LCR测量仪测定叶片在0.05~200 k Hz下的相对介电常数ε′和介质损耗因数ε″,并采用干燥法测量叶片含水率。利用迭代保留信息变量法(iteratively retains informative variables,IRIV)对介电参数进行特征变量选取,并与连续投影算法(successive projections algorithm,SPA)进行比较,利用支持向量回归机(support vector regression,SVR)分别建立叶片全变量、2种特征变量与叶片含水率的关系模型。结果表明,基于迭代保留信息变量法选取特征变量的支持向量回归模型(IRIV-SVR)具有良好的预测能力,但预测精度仍需提高,故引入灰狼优化算法(grey wolf optimizer,GWO)优化模型的参数c(惩罚因子)和g(核函数参数)。最终,经GWO优化后的模型(IRIV-GWO-SVR)的预测集决定系数R2与均方根误差RMSE分别为0.963 8,0.020 7。因此,利用介电特性结合IRIV-GWO-SVR算法预测番茄叶片含水率是可行的,同时为其他叶片含水率检测提供了一种新的方法和思路。 相似文献
8.
采煤沉陷后风沙土理化性质变化及其评价研究 总被引：10，自引：0，他引：10
对毛乌素沙地南缘补连塔矿采煤沉陷后风沙土理化性质的变化进行了研究。与对照区相比,沉陷2a间沉陷区土壤含水量普遍显著减小(p<0·05),而在沉陷2a后,沉陷区的地表沉陷边界处风沙土孔隙度显著增大(p<0·05),而容重、硬度显著减小(p<0·05),沉陷区局部地表开裂地段全氮、全磷含量显著减小(p<0·05),全钾与有机质含量无显著变化(p>0·05)。通过主成分分析得到研究区样地前2个主成分值的散点图,用以反映沉陷后风沙土理化性质的综合变异性,对采煤沉陷后土壤质量评价进行了探索。 相似文献
9.
P. O. Aina 《植物养料与土壤学杂志》1980,143(3):317-323
A greenhouse study was conducted to evaluate the performance of maize (Zea mays L.) on Iwo Soil in relation to different levels of soil moisture, soil compaction and K fertilization. Reductions in dry matter yields of maize were closely associated with soil moisture stress and compaction. There was significant interaction between soil moisture and bulk density, with highest yields occurring at 17% and 21% soil moisture levels for 1.6 and 1.2 g/cm3 bulk densities, respectively. Moisture stress and compaction resulted in greater reductions in the yield of roots than that of shoot. Yield and K uptake were more adversely affected by compaction compared to soil moisture stress. Addition of K increased yield and plant K content but the 60 ppm and 120 ppm rates were not significantly different in terms of improving crop performance. Implications of the results relative to long-term management of Iwo Soil are discussed. 相似文献
10.
基于同心轴圆筒式电容传感器的花生仁水分无损检测技术 总被引：3，自引：2，他引：1
为了实现花生仁含水率的快速准确检测,设计了以MSP430单片机为控制芯片的花生仁含水率检测仪,利用圆筒式电容传感器、温度传感器和称质量传感器分别检测花生仁的电容、温度和容积密度,通过信号检测调理电路进行测量信号电容到频率的转换,单片机进行数据处理后计算出花生仁含水率,在液晶屏上显示检测结果,并将检测数据存储到内存卡中。进一步研究了含水率、温度和容积密度对频率的影响规律,建立了描述含水率与差频、温度的数学模型,并验证了基于电容法检测花生含水率的可行性和模型的可靠性。试验表明,在含水率6.4%~18.2%、温度10~40℃范围内,该检测仪的测量相对误差绝对值小于0.5%。该研究为快速无损检测花生仁含水率提供了参考。 相似文献
11.
电介质型水分传感器测定栽培基质含水率的标定模型 总被引：2，自引：1，他引：1
土壤与基质的理化特性相差较大,土壤水分传感器测定基质含水率时有较大误差,不能直接用于基质含水率测定。为实现栽培基质水分快速检测,在不同配比的基质中采用电介质型EC-5土壤水分传感器进行了适应性测试。试验研究了温度、体积质量和电导率对传感器输出值的影响,采用多项式和线性回归处理方法,建立了基于温度、体积质量影响下的基质含水率标定模型。试验表明,经标定后,EC-5电介质型土壤水分传感器的测定含水率与实际含水率之间有较好的线性关系（R2＞0.9791）,且最大误差小于13%,因此,EC-5电介质型土壤水分传感器经标定后可作为基质的快速检测设备。 相似文献
12.
以小兴安岭阔叶红松林林隙为研究对象,采用地统计学方法对林隙0～20 cm和20～40cm土层土壤物理性质的微环境异质性进行分析。结果表明:阔叶红松林林隙表层土壤含水量、饱和持水量、毛管持水量和孔隙度均大于下层,但土壤密度相反;表层土壤物理性质有相对高的极差和变异系数。土壤物理性质总空间异质性程度和由空间自相关引起的异质性均为表层土壤高于下层。土壤含水量表现出明显各向异性,土壤孔隙度趋近于各向同性,其他3个物理因子随空间距离增大而表现出各向异性。表层土壤物理性质在空间自相关范围内变异函数相互影响较小。不同层次土壤物理性质空间分布均以中低等级斑块为主,相对较高等级的斑块仅分布在020cm土层中,并位于林隙中心以北的范围内。 相似文献
13.
This study was conducted to develop a ready‐to‐eat extruded food using a single‐screw laboratory extruder. Blends of Indian barley and rice were used as the ingredients for extrusion. The effect of extrusion variables and barley‐to‐rice ratio on properties like expansion ratio, bulk density, water absorption index, hardness, β‐glucan, L*, a*, b* values, and pasting characteristics of extruded products were studied. A central composite rotatable design was used to evaluate the effects of operating variables: die temperature (150–200°C), initial feed moisture content (20–40%), screw speed (90–110 rpm), and barley flour (10–30%) on properties like expansion ratio, bulk density, water absorption index (WAI), hardness, β‐glucan, L*, a*, b* values, and sensory and pasting characteristics of extruded products. Die temperature >175°C and feed moisture <30% resulted in a steep increase in expansion ratio and a decrease in bulk density. Barley flour content of 10% and feed moisture content of <20% resulted in an increased hardness value. When barley flour content was 30–40% and feed moisture content was <20%, a steep increase in the WAI was noticed. Viscosity values of extruded products were far less than those of corresponding unprocessed counterparts as evaluated. Rapid visco analysis indicated that the extruded blend starches were partially pregelatinized as a result of the extrusion process. Sensory scores indicated that barley flour content at 20%, feed moisture content at 30%, and die temperature at 175°C resulted in an acceptable product. The prepared product was roasted in oil using a particular spice mix and its sensory and nutritional properties were studied. 相似文献
14.
Extrusion with CO2 injection was developed to simplify the process of producing vacuum‐puffed yukwa (rice snacks). The effects of feed moisture content and CO2 injection on the characteristics of extruded pellets (maximum viscosity and degree of gelatinization) and vacuum‐puffed yukwa (expansion ratio, bulk density, hardness, and color) were investigated. Higher feed moisture increased the size of vacuum‐puffed yukwa and the degree of gelatinization, whereas the maximum viscosity decreased. Maximum viscosity and gelatinization degree of extruded pellets were highly correlated with expansion ratio, bulk density, hardness, and color values of vacuum‐puffed yukwa. Increasing feed moisture content significantly increased expansion ratio but decreased bulk density and hardness. CO2 injection decreased bulk density and hardness of vacuum‐puffed yukwa. 相似文献
15.
芒萁是最早侵入红壤退化裸地的先锋植物,其侵入过程对土壤环境的改变在退化裸地生态恢复进程中具有重要意义。以福建省长汀县红壤侵蚀裸地为研究对象,分析测定退化裸地中芒萁侵入区和非侵入区土壤理化性质和细菌组成及多样性。结果表明：芒萁侵入裸地显著提高土壤最大持水量、土壤含水率、全碳、全氮、全钾、有机质和pH,并显著降低土壤容重;芒萁侵入区增加根瘤菌目和慢生根瘤菌属等14种土壤优势细菌,变形菌门和甲型(α)变形杆菌的相对丰度显著提高(p<0.05),而土壤绿弯菌门和AD3菌纲的相对丰度显著降低(p<0.05),这些土壤细菌主要功能为化能异养、好氧化能异养和纤维素分解;芒萁侵入裸地显著提高土壤细菌群落结构多样性(p<0.05);芒萁侵入区和非侵入区土壤细菌群落结构差异显著(p<0.05);土壤细菌群落结构的主要影响因子是土壤含水率、全碳、有机质、土壤容重和pH。这些影响因子与疣微菌门、变形菌门、疣微菌纲和甲型(α)变形杆菌纲正相关。综上所述,芒萁侵入后可显著改善红壤侵蚀退化裸地的土壤理化性质,改善土壤细菌群落组成,增加土壤细菌群落多样性和优势菌群,对土壤细菌群落有积极效应。 相似文献
16.
多因素影响下浑水膜孔肥液入渗土壤水分运移特性 总被引：2，自引：0，他引：2
为研究不同因素对浑水膜孔肥液入渗土壤水分运动特性的影响,开展室内土箱入渗试验,试验设土壤初始含水率、土壤容重、含沙率和肥液浓度4因素,每个因素设3个水平,共12组试验(9组正交试验,3组验证试验)。分析影响因素对浑水膜孔灌肥液入渗单位膜孔面积累积入渗量、入渗率及湿润体平均体积含水率增量的影响。利用多元回归推求并验证单位膜孔累积入渗量和湿润体平均体积含水率增量与影响因素的经验模型和模型参数。结果表明:土壤初始含水率、土壤容重、含沙率和肥液浓度对单位膜孔累积入渗量影响极显著(P<0.01),各影响因素影响程度由大到小依次为含沙率、土壤容重、土壤初始含水率、肥液浓度;土壤初始含水率、含沙率和肥液浓度对湿润体平均体积含水率增量影响极显著(P<0.01),土壤容重对其影响显著(P<0.05),各影响因素影响程度由大到小依次为土壤初始含水率、肥液浓度、含沙率、土壤容重。建立的经验模型及模型参数检验合格,预测值与实际测算值误差均在±10%以内,精度良好,可用于试验因素不同时土壤水分入渗情况预测。 相似文献
17.
Wojciech Skierucha 《植物养料与土壤学杂志》2009,172(2):186-193
The purpose of this study is to determine the temperature influence on the soil bulk dielectric permittivity, ?b, calculated from the measurement of the electromagnetic‐wave velocity of propagation along the parallel waveguide in a TDR probe, i.e., a probe working in time domain reflectometry technique. The experimental evidence shows that the existing models do not completely describe the temperature effect. However, it has been confirmed that the observed temperature effect is the result of two competing phenomena: ?b increases with temperature following the release of bound water from soil solid particles, and ?b decreases with temperature increase following the temperature effect of free water molecules. It has been found that there is a soil type–characteristic moisture value, θeq, named the equilibrium water content, at which both competing phenomena compensate each other. The equilibrium water content, θeq, is correlated with the soil specific surface area. Based on knowledge of θeq, a temperature‐correction formula is presented that adjusts the TDR soil‐moisture measurements at various temperatures to the corresponding value at 25°C. This decreases the absolute measurement error of soil moisture, θTDR, by the factor of 2 as compared to the uncorrected values. 相似文献
18.
不同植被对土壤理化性质影响——以王东沟小流域为例 总被引：2，自引：1，他引：2
[目的]分析陕西省长武县王东沟流域9个径流小区不同植被覆盖条件对土壤理化性质的影响,为黄土高原生态建设提供科技支持。[方法]采用环刀法、定水头法以及重铬酸钾外加热法等分层测定0—40cm间土壤容重、毛管持水量、饱和持水量、饱和倒水率以及有机质含量。[结果]饱和持水量、毛管持水量、土壤有机质表现为草、灌地显著优于纯林和混交林,而土壤容重、饱和导水率各小区间差异不显著。[结论]草地和沙棘灌木林地土壤理化性质高于其他植被组合,培肥土壤,涵养水源,利于保水保土。侧柏纯林的土壤理化性质最差,水保效益最低。 相似文献
19.
《Land Degradation \u0026amp; Development》2017,28(5):1752-1762
Spatial variability of hydro‐physical properties has long been observed, whereas temporal variation is much less documented and considered in studies and applications, particularly of paddy clay soils under different cropping systems. The objective of this study was therefore to assess the seasonal‐ and inter‐seasonal variation of selected hydro‐physical properties of a paddy clay soil under different rice‐based cropping systems with contrasting tillage. In a long‐term experiment, plots were arranged in a randomized complete block design with four treatments and four replications: (i) rice–rice–rice; (ii) rice–maize–rice; (iii) rice–mung bean–rice; and (iv) rice–mung bean–maize. Soil samples were collected at three depths (0–10, 10–20 and 20–30 cm) at three times during two cropping seasons, i.e., 15 days after soil preparation (DASP), 45 DASP and 90 DASP during the winter–spring and spring–summer seasons. Results show that temporal variability of soil bulk density, macro‐porosity (MacP) and matrix‐porosity within both seasons and between seasons was limited for cropping systems with upland crop rotations, whereas within season variation was significant for rice monoculture system. Observed variation in bulk density, matrix‐porosity and MacP was mainly associated with cropping system and soil depth. Field saturated hydraulic conductivity of topsoil showed great temporal variability, both seasonal and inter‐seasonal, in correspondence with MacP (r = 0·58). These results highlight the need of depth differentiated soil sampling and time consideration when evaluating management practices on soil physical properties and modeling the hydrological behavior of paddy soil. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
20.
Chao Ye Zhonglu Guo Chongfa Cai Junguang Wang Jia Deng 《Journal of Soils and Sediments》2017,17(1):210-219