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1.
Continuous paddy rice cultivation requires fields to be flooded most of the time limiting seriously the collection of detailed soil information. So far, no appropriate soil sensor technology for identifying soil variability of flooded fields has been reported. Therefore, the primary objective was the development of a sensing system that can float, acquire and process detailed geo-referenced soil information within flooded fields. An additional objective was to determine whether the collected apparent electrical conductivity (ECa) information could be used to support soil management at a within-field level. A floating sensing system (FloSSy) was built to record ECa using the electromagnetic induction sensor EM38, which does not require physical contact with the soil. Its feasibility was tested in an alluvial paddy field of 2.7 ha located in the Brahmaputra floodplain of Bangladesh. The high-resolution (1 × 1 m) ECa data were classified into three classes using the fuzzy k-means classification method. The variation among the classes could be attributed to differences in subsoil (0.15–0.30 m below soil surface) bulk density, with the smallest ECa values representing the lowest bulk density. This effect was attributed to differences in compaction of the plough pan due to differential puddling. There was also a significant difference in rice yield among the ECa classes, with the smallest ECa values representing the lowest yield. It was concluded that the floating sensing system allowed the collection of relevant soil information, opening potential for precision agriculture practices in flooded crop fields.  相似文献   

2.
Apparent soil electrical conductivity (ECa) has shown promise as a soil survey tool in the Midwestern United States, with a share of this interest coming from the precision agriculture community. To fully utilize the potential of ECa to map soils, a better understanding of temporal changes in ECa is needed. Therefore, this study was undertaken to compare temporal changes in soil ECa between different soils, to investigate the influence of changes in soil water content on soil ECa, and to explore the impacts these ECa changes might have on soil mapping applications. To this end, a 90 m long transect was established. Soil ECa readings were taken in the vertical and horizontal dipoles at five points once every one to two weeks from June until October in 1999 and 2000. At the same time, soil samples were collected to a depth of 0.9 m for volumetric soil water content analysis. Soil ECa readings were compared to soil water content. At four of the five sites linear regression analysis yielded r 2 values of 0.70 or higher. Regression line slopes tended to be greater in lower landscape positions indicating greater ECa changes with a given change in soil water content. Two of the soils had an ECa relationship that changed as the soils became dry. This is an item of concern if ECa is to be used in soil mapping. Results indicated that soil water content has a strong influence on the ECa of these soils, and that ECa has its greatest potential to differentiate between soils when the soils are moist. Soil water content is an important variable to know when conducting ECa surveys and should be recorded as a part of any report on ECa studies.  相似文献   

3.
The general objective of this study was to evaluate the stability of patterns of apparent soil electrical conductivity (ECa) in dry versus wet soil conditions in a shallow soil typically used for pastures in Mediterranean conditions of the southern region of Portugal. A 6 ha experimental field of permanent bio-diverse pasture was divided into 76 squares of 28 × 28 m. The soil electrical conductivity was measured using a Dualem 1S sensor under dry conditions (June 2007) and under wet conditions during the rainy season (March 2010). Soil samples, geo-referenced with GPS, were collected in a depth range of 0–0.30 m. The soil was characterized in terms of bedrock depth, moisture content, texture, pH, organic matter content, and macronutrients (nitrogen, phosphorus, and potassium). Pasture samples, also geo-referenced with GPS, were collected to measure the pasture dry matter yield. The statistical analysis of apparent electrical conductivity between dry and wet soil conditions resulted in a linear significant correlation coefficient (R = 0.88). The results also showed a significant correlation between apparent electrical conductivity and the relative field elevation (R = ?0.64 and R = ?0.66), the pasture dry matter yield (R = 0.42 and R = 0.48), the bedrock depth (R = 0.40 and R = 0.27), the pH (R = 0.50 and R = 0.49), the silt (R = 0.27 and R = 0.38) and soil moisture content (R = 0.48 and R = 0.45), in dry and wet conditions, respectively. A multi-variate regression was carried out using the following soil parameters that showed significant correlation with ECa and that did not present multi-collinearity: pH, bedrock depth, silt and moisture content. The results showed, in dry and wet conditions, that the analysis was significant (R = 0.75 and R = 0.84, respectively). Overall, these results indicate the temporal stability of ECa patterns under different soil moisture contents, which is relevant with respect to the time when a field should be surveyed and is important for using the electrical conductivity sensor, as a decision support tool for management zones in precision agriculture.  相似文献   

4.
Mediterranean olive trees traditionally grow under rainfed conditions, on poor soils with steep slopes. Rainfall is mainly concentrated during autumn and winter and is characterized by intense rain pulses, separated by dry periods. The use of electromagnetic induction (EMI) techniques in these olive orchards might be questioned since EMI surveys are generally recommended to be performed under moist soil conditions. A 6.7 ha olive orchard was surveyed for EMI-based apparent electrical conductivity (ECa), both under wet and dry soil conditions. In addition, 48 soil samples were analyzed for soil texture and for soil water content (SWC) under both soil conditions. The relationships between ECa, soil texture and SWC, under both soil conditions were evaluated. Despite the significantly larger ECa values measured during the wet survey as compared to the dry survey, a similar spatial correlation structure was found, indicating temporally stable ECa patterns. Significant correlations (r) were found between both surveys for ECa (r = 0.67) and for SWC (r = 0.63). The correlation between SWC and clay content exceeded 0.60 for both surveys, and the correlation between ECa and clay content was twice as high under wet soil conditions as compared to dry soil. In both situations, the ECa surveys revealed the same patterns of soil texture, indicating that moist soil conditions are not an absolute prerequisite for the use of EMI to map the spatial variability of these soil properties. Nonetheless, measuring the ECa under different moisture conditions can provide additional information about soil moisture dynamics.  相似文献   

5.
The general objectives of this study were to evaluate (i) the specificity of the spatial and temporal dynamics of apparent soil electrical conductivity (ECa) measured by a electromagnetic induction (EMI) sensor, over 7 years, in variable conditions (of soil moisture content (SMC), soil vegetation cover and grazing management) and, consequently, (ii) the potential for implementing site-specific management (SSM). The DUALEM 1S sensor was used to measure the ECa in a 6 ha pasture experimental field four times between June 2007 and February of 2013. Soil spatial variability was characterized by 76 samples, geo-referenced with the global positioning system (GPS). The soil was characterized in terms of texture, moisture content, pH, organic matter content, nitrogen, phosphorus and potassium. This study shows a significant temporal stability of the ECa patterns under several conditions, behavior that is an excellent indicator of reliability of this tool to survey spatial soil variability and to delineate potential site-specific management zones (SSMZ). Significant correlations were obtained in this work between the ECa and relative field elevation, pH, silt and soil moisture content. These results open perspectives for using the EMI sensor as an indicator of SMC in irrigation management and of needs of limestone correction in Mediterranean pastures. However, it is interesting to extend the findings to other types of soil to verify the origin of the lack of correlation between the ECa data measured by DUALEM sensor and properties such as the clay, organic matter or phosphorus soil content, fundamental parameters for establishment of pasture SSM projects.  相似文献   

6.
采用单因素重复试验研究不同灌溉模式对稻田土壤微生物数量的影响.研究结果表明,不同灌溉模式,稻田土壤微生物数量不同,淹水条件下厌气性细菌数量高于其他灌溉模式的数量,好气性细菌、真菌和放线菌以及稻田土壤微生物总量以浅、湿、干间歇灌溉的最高,原因是由于该灌溉模式的土壤湿度适于微生物的生长.  相似文献   

7.
Soil electrical conductivity (ECa) measured by electromagnetic induction (EM) using the EM-38 has shown promise as a soil survey tool. Soil temperature influences ECa readings, and temperature can fluctuate considerably in the upper 10cm of the soil during a day. ECa readings were taken in the horizontal and vertical dipole orientations once an hour from 8a.m. to 8p.m. at four sites on three separate days to determine if ECa values were influenced by diurnal temperature variations. Soil temperature readings were taken at the same times at four depths. EM-38 readings remained steady at all four sites all 3days. Linear regression analysis when temperature in the upper 10cm was plotted against ECa yielded low r 2 values and slopes, indicating no correlation between soil temperature in the upper 10cm and ECa values. Diurnal changes in soil temperature do not significantly influence soil ECa readings obtained with the EM-38 under the conditions encountered during the study.  相似文献   

8.
The adoption of precision viticulture requires a detailed knowledge of variation in soil chemical, physical and profile properties. This study evaluates the usefulness of apparent electrical conductivity (ECa) data within a GIS framework to identify variations in soil chemical and physical properties and moisture content. The work was conducted in a vineyard located in the Carneros Region (Napa Valley, California). The soil was sampled using 44 boreholes to quantify chemical and physical characteristics and 9 open pits to verify the borehole observations. Moisture content was determined using time domain reflectometry (TDR). To characterize soil ECa, three campaigns were undertaken using a soil electrical conductivity meter (EM38). Linear regressions between soil ECa and soil properties were determined. Boreholes and TDR data were interpolated by kriging to characterize the spatial distribution of soil variables. The resulting maps were compared to the results obtained using the best ECa linear regressions. Using ECa measurements, soil properties like extractable Na+ and Mg2+, clay and sand content were well estimated, while best estimates were obtained for extractable Na+ (r 2  = 0.770) and clay content (r 2  = 0.621). The best estimates for soil moisture content corresponded to moisture in the deeper soil horizons (r 2  = 0.449). The methods described above provided maps of soil properties estimated by ECa in a GIS framework, and could save time and resources during vineyard establishment and management.  相似文献   

9.
The nitrogen (N) sufficiency approach to assess plant N status for in-season N management requires a non-N-limiting reference to make N recommendations. Use of reference strips in fields with spatially variable soils and the impact this variability has within N enriched reference strips are not well understood. Consequently three strategies were investigated to evaluate the impact of spatially variable sandy soils within reference strips in two commercial center pivot-irrigated corn fields. Evaluation strategies were: (i) ignore soil spatial variability throughout the reference strips, (ii) account for soil variability in the reference strips based on second-order NRCS soil map units, and (iii) account for soil variability based on apparent electrical conductivity (ECa) data as a surrogate for soil texture differences in the reference strips. A sufficiency index (SI) calculated from radiometer measured canopy reflectance data (SIsensor) and from SPAD chlorophyll meter data (SImeter) at two growth stages during corn vegetative growth were used to assess N sufficiency within the N enriched reference strips. By ignoring soil spatial variability in the reference strips, corn in the sandier soils was designated N deficient. Accounting for soil spatial variability using NRCS soil mapping units improved N sufficiency designations of corn in the reference strip for the different soil types contained within the reference strip but tended to designate corn in lighter texture areas within a mapping unit as N deficient. Use of ECa as a surrogate for soil texture typically performed best for classifying corn N sufficiency throughout the reference strip and is recommended as a method to obtain reference strip normalizing values in fields with spatially variable sandy soils.  相似文献   

10.
土壤盐渍化问题是制约干旱半干旱区植被生长最主要的生态环境地质问题,也是影响绿洲农业生产的障碍性问题。而将遥感与近感技术相结合,是当前评价、监测及预报土壤盐渍化程度的先进方法。以新疆塔里木盆地北缘的渭干河-库车河三角洲绿洲为例,以遥感数据和解译后的电磁感应数据为基础数据源,利用解译后的数据结合GIS和地统计学知识以及野外实测所得到的土壤电导率和盐分资料,分别采用泛克里格(Universal Kriging)、光谱指数回归(Spectral Index Regression)和回归残差泛克里格(Regression-Universal Kriging)3种方法研究了该地区两个关键季节(干季和湿季)土壤盐分的空间变异特征。研究结果表明:研究区的土壤浸提液电导率EC1:5和土壤盐分呈现显著相关,可以用EC1:5来代替土壤的全盐量进行分析;电磁感应仪(EM38)所测各季节土壤表观电导率与EC1:5的相关系数均达到1%显著水平,以表观电导率垂直读数(EMV) 和水平读数(EMH)为自变量的多元回归模型拟合效果较好;研究区各季节的表层土壤电导率的空间分布均表现为强相关性,说明土壤采样点间的内部结构性良好,采用能够充分考虑到干旱区表层土壤电导率空间变异的尺度依赖性的球状套合模型,能够更好的拟合土壤表观电导率的空间结构;经过精度比较,回归残差泛克里格法为最优预测方法,这表明将遥感和电磁感应技术相结合,能够有效的提高预测与评估土壤盐分空间分布的精度,为精确地进行土壤盐分预测以及土壤次生盐渍化的防控提供了一定的依据。  相似文献   

11.
为探讨干湿交替和模拟氮沉降对高寒湿地土壤CO_2排放的规律,以新疆巴音布鲁克高寒湿地土壤为研究对象,通过室内模拟控制试验,研究水分变化下[100%、70%、50%、40%和25%WFPS(土壤充水孔隙度Water filling soil porosity)]氮添加N0(0 kg·hm~(-2)·a~(-1))、N10(10 kg·hm~(-2)·a~(-1))和N100(100 kg·hm~(-2)·a~(-1))处理对巴音布鲁克高寒湿地土壤CO_2排放的影响。研究结果表明:土壤CO_2排放速率及累积排放量随WFPS值及氮添加量的增大而增加。一个循环,土壤由干到湿的过程中,初期土壤CO_2排放速率最高,随后随着水分减少,土壤CO_2排放速率呈降低趋势;首次干湿循环土壤CO_2累积排放量最大。土壤TN、NO_3~--N、NH_4~+-N、SOC含量均随土壤水分和氮添加量的增加而增加,而土壤SON随土壤水分和氮添加量的增加而减少。水分与土壤CO_2排放速率呈极显著正相关,氮添加与CO_2排放亦呈正相关。除了土壤SON、SOC含量与土壤CO_2排放速率呈负相关关系外,土壤TN、NO_3~--N、NH_4~+-N与CO_2排放都呈现出正相关关系。  相似文献   

12.
以广西桂林市农业科学院大豆、甘蔗及梨树植被覆盖的土壤为例,研究不同土地利用模式下土壤斥水性的空间变化。通过对每个试验区面积为135 m×105 m的100个测量点应用滴水穿透时间法(water drop penetration time,WDPT)进行土壤斥水性测量,利用土壤含水量确定干旱(0.062±0.025)cm~3·cm~(-3)、中等(0.151±0.045)cm~3·cm~(-3)和湿润(0.237±0.086)cm~3·cm~(-3)的土壤水分条件。运用地统计方式,对土壤斥水性进行空间变化分析。结果表明:在干旱和湿润水分条件下,WDPT的大小均表现出梨树地最大,甘蔗地次之,大豆地最小,与土壤含水量和有机质大小的变化一致,但是在中等水分条件下,WDPT均值大豆地高于甘蔗地,同时3个试验区的滴水入渗持续时间都达到最大。土壤斥水性的地统计分析结果表明,在3种水分条件下,3个试验区的空间结构比基本上大于75%,空间相关性较强。在土壤斥水性的高阈值空间分布上,甘蔗地的稳定性比大豆地强,而梨树的空间分布稳定性最弱。研究结果说明人类的活动会对土壤斥水性空间稳定性产生干扰,但土壤本身仍具有恢复其空间分布稳定性的能力。  相似文献   

13.
Site-specific application of nitrogen (N) to maize (Zea mays L.) may provide economic and environmental benefits. Variations in soil drainage and texture within fields are often believed to cause localized differences in soil N availability and therefore are a potential basis for site-specific N fertilizer application. The objective of this study was to evaluate the effect of imposed variations in drainage conditions in two soils on early season soil water conditions, soil nitrate levels, and crop response to N fertilizer. Maize was grown for three years following conversion from sod. Two soil drainage regimes and three N rates (22, 100 and 134 kg ha–1) were experimentally imposed on plots on two soil types, a clay loam and a loamy sand. Soil water potential and soil nitrate content were intensively monitored for the 0–150 and 150–300 mm soil layers during the early growing season. Early season soil water potentials showed small effects of drainage variability at the 75 and 225 mm depths. However, the clay loam soil experienced prolonged periods of saturation after significant precipitation, while the loamy sand never experienced such conditions. Soil nitrate levels were strongly affected by cropping history, but were also subjected to losses as a result of precipitation and short-term soil saturation. Maize N response was minimally affected by differences in soil drainage conditions in all 3 years. In years with a wet spring, justification exists for higher N fertilizer rates on finer-textured soils. This study therefore showed only moderate potential for varying N application within fields based on soil type and drainage conditions, but suggests that seasonal differences in N dynamics greatly affect maize N response.  相似文献   

14.
蒲智  孟晓燕  陈艳红  吴艳 《安徽农业科学》2013,(26):10867-10869
地物光谱特征是遥感机理的重要内容,也是遥感应用研究的重要依据.盐碱土的反射光谱特性反映了盐碱土的理化特征.以干旱区3种典型的盐碱土为研究对象,测量了不同含盐量和含水率的土壤反射率光谱,并分析了其光谱特征.结果表明,3种盐碱土的光谱反射率在干燥状态下有明显的高低规律.经过去包络线处理后,3种盐碱土在干燥状态下具有明显不同的光谱特征,且在干湿两种状态下,两个水分吸收谷处的吸收深度的深浅均具有明显的深浅差异.根据这些特征可以将3种类型的盐碱土区分出来.研究结果可为今后进一步研究盐碱化土壤参数反演和分类,以及盐碱土监测等遥感应用服务.  相似文献   

15.
薏苡干物质积累特性的研究   总被引：3，自引：0，他引：3  
本文分析了不同品种和不同栽培条件下薏苡的干物质积累和分配特性,结果表明,薏苡一生的干物质积累动态表现为“Ｓ”型曲线,但不同品种之间差异较大,杂交种表现出较强的杂种优势,峨嵋黑壳品种较长春黑壳品种表现出更强的适应性和旺盛的生命力;全生育期都处于淹水条件（水生栽培）的植株不及栽培于湿润旱地条件（旱生栽培）的长得好,干物质积累量较旱生栽培的低;干物质在各器官中的分配因生育时期而异,亦在一定程度上受栽培条件影响,生育后期主要分配到茎秆和穗子,水生栽培下的植株根系特别发达,根系的干物质分配百分率较高。  相似文献   

16.
研究秸秆覆盖和植被（田菁）覆盖条件下滨海盐土土壤水盐的动态变化规律,为沿海滩涂盐碱地脱盐改良提供依据。本研究以含盐量6.98 g·kg-1的滨海盐土为研究对象,设置秸秆覆盖和种植田菁2种覆盖处理,以裸地为对照,研究不同覆盖处理对滨海盐土土壤含水量和土壤盐分动态变化的影响。结果表明：秸秆覆盖下的土壤含水量（27.58%）显著高于田菁覆盖（26.70%）和裸地（26.61%）,后两者差异未达显著水平。处理1年后0~20、20~40 cm土层的秸秆覆盖、田菁覆盖和裸地不同处理间土壤含盐量的差异均达显著或极显著水平;秸秆覆盖处理的脱盐率为田菁覆盖处理的2倍。回归分析表明裸地和田菁覆盖下土壤盐分含量与累积降雨量的关系可用二次多项式拟合,田菁覆盖下的淋洗方程（ECa/ECi与Dw/Ds间的关系）可用三次多项式拟合;而秸秆覆盖条件下土壤盐分含量与累积降雨量的关系、淋洗方程均表现为指数函数关系y=aebx（P<0.01）。秸秆覆盖条件下滨海滩涂0~40 cm土层脱盐80%需要386.8 mm的累积降雨量。结果表明秸秆和植被覆盖技术在江苏滨海盐土可获得较好的脱盐效果,具有较好的应用前景。  相似文献   

17.
土壤机械阻力对草地早熟禾根系生长的影响   总被引：1，自引：0，他引：1  
该文研究了不同沙土配比根系层在干湿状态下土壤机械阻力的变化规律,以及对草地早熟禾根系生长的影响。试验将沙土配比设为11个处理,即m(沙)∶m(沙＋土)从0～100%,每10%为1个梯度。结果表明:处于湿润状态下的土壤机械阻力低于干燥状态下的,随含沙量的增加,两种状态下土壤机械阻力均呈现中间高两边低的变化趋势,在含沙量为50%～60%（即沙粒含量70%～80%）时,土壤机械阻力达到最大值;随含沙量增加,根系生物量及根冠比先降后升,根系总长度、根系表面积及根尖数与沙粒含量均呈显著的指数函数关系,表明含沙量增大到一定程度时,对于根系分蘖、增加根系总量具有促进作用;根系平均直径随沙粒含量增加,呈现先增加后降低趋势,在含沙量为40%～50% (即沙粒含量60%～70%)达到最大值,与土壤机械阻力呈线性正相关。   相似文献   

18.
Electromagnetic induction sensors, such as EM38, are used widely for monitoring and mapping soil attributes via the apparent electrical conductivity (ECa) of the soil. The sensor response is the depth-integrated combination of the depth-response function of the EM38 and ‘local’ electrical conductivity (ECaz) at depth. In deep, Vertosol soils, assuming the instrument depth-response function is not perturbed by the soil and where volumetric moisture content at depth (θv(z)) dominates ECaz, EM38 should be capable of predicting average moisture content without recourse to mathematically complicated, and unstable profile inversion processes. Firstly a multi-height EM38 experiment was conducted over deep Vertosol soils to confirm the veracity of the EM38 depth-response function and test the concomitant hypothesis of the EM38 response being an integrated (i.e. additive) combination of depth-response function and θv(z). Secondly, depth profiles of moisture content were used to calibrate the EM38 to infer average θv(z) within the ‘root-zone’ of crop plants—here taken to be surface—0.8 m and surface—1.2 m. EM38 calibration was performed using soil samples acquired from both extracted cores and excavated pits. Mathematical summation of measured θv(z) from sectioned cores and the known depth-response function of the EM38 was found to explain 99% and 97% of the variance in measured ECa for horizontal and vertical dipole configurations at multiple sensor heights above the ground. Average θv from surface to 0.8 m () and surface to 1.2 m () explained only 37% and 46% of the variance in on-ground ECa for vertical dipole configuration measurements compared to 55% and 56% of the variance for horizontal dipole configuration. In a separate validation experiment, the shape of the vertical moisture profile proved highly influential in determining the ability of the calibration equations to infer underlying average moisture content, especially where the depth profile shapes differed between sensor calibration and subsequent field validation (for example following rainfall or irrigation).  相似文献   

19.
A world-wide need to use water resources efficiently necessitates more effective approaches to study water and contaminant transport in soil. This study examined the effectiveness of a multi-receiver electromagnetic induction probe (Geonics EM31-3RT) and modeling software (EMIGMA) to delineate hydrological regimes at field scale. The site consisted of 20 (15 m × 15 m) tile-drained plots in Southern Ontario, Canada. Measurements of apparent soil electrical conductivity (ECa) and magnetic susceptibility were obtained using the EM31-3RT in each plot at four distances (0, 2.25, 4.5 and 7.5 m) from the tile drain, and on three occasions (August 22, 26 and 29) in 2003. The EMIGMA was used to simulate a depth profile of electrical conductivity (ECs) from EM31-3RT readings. The near-surface soil showed significantly (p < 0.01) smaller ECa values than at greater depth. The ECa measurements made directly over the tile drains were smaller than those observed further away due to the presence of the drains. Cluster analysis indicated that the largest ECa values were at the lower elevations of the site related to the redistribution of moisture from higher elevations. The effect of tile drains and rainfall events on ECa was simulated well by EMIGMA, with smaller ECs values above the drains compared to further away, and showing an increase in ECs in the near-surface soil after rain. This study suggests that EM31-3RT measurements combined with EMIGMA simulation of electrical conductivity can provide valuable information on depth profiles of ECa and water dynamics in soil.  相似文献   

20.
Soil hydraulic parameters are essential inputs to agricultural and hydrologic models for simulating soil moisture. These parameters however are difficult to obtain especially when the application is aimed at the regional scale. Laboratory and field methods have been used for quantifying soil hydraulic parameters but they are proved to be laborious and expensive. An emerging alternative of estimating soil hydraulic parameters is soil moisture model inversion using remote sensing (RS) data. Although soil hydraulic parameters could not be derived directly from remote sensing, they could be quantified by the inverse modeling of RS data. In this study, we conducted a multi-criteria inverse modeling approach to estimate the rootzone soil hydraulic parameters in a rainfed rice field at depths 3, 12, 28 and 60 cm, respectively. The conditioning data used in the inverse modeling are leaf area index (LAI) and actual evapotranspiration (ETa) from satellite imageries, and soil moisture (SM) data from in situ measurements. The performances of all the model inversion experiments were evaluated against observed soil moisture in the field, and measured LAI during the growing season. The results showed that using remotely sensed LAI and ETa in the inverse modeling provided a good matching between observed and simulated soil moisture down to 28 cm depth from the soil surface. With the addition of soil moisture information from the site, the model inversion significantly improved the soil moisture simulation up to a depth of 60 cm.  相似文献   

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