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1.
冬小麦冠气温差及其相关影响因素关系研究 总被引：7，自引：0，他引：7
在冬小麦主要生育期(2002年的4月初到5月底),对3个不同水分处理测定了冠层温度、气温以及土壤含水率和叶面积指数,并进一步计算了冠气温差并分析了冠气温差与土壤含水率和叶面积指数间的关系。结果表明:不同的灌溉措施对冠气温差的影响是有差异的;中午14:00左右在H2高度处(冠层之上)的冠气温差能反映作物的水分特征,可以用此时刻的实验结果来检验遥感数据反演冠气温差的精度;在60～80cm土层的土壤体积含水率能较好地反映中午14:00冠层之上冬小麦冠气温差的变化情况,不同水分处理二者的相关系数(R2)分别为0.60361(节水灌溉),0.95668(充分灌溉),0.84597(不灌溉);不同水分处理下的冬小麦主要生育期的叶面积指数与冠气温差也有一定的相关性,冠层之上二者的相关系数分别为:0.76082(节水灌溉),0.40548(充分灌溉),0.99499(不灌溉),这为区域上遥感反演作物冠气温差来监测土壤含水率及作物估产提供了依据。 相似文献
2.
为了评估时域反射仪测定水分非均匀分布土壤的含水率的性能，该研究在室内试验中将土柱纵向分为上下2层，设置土壤水分差为0.05、0.10和0.15 cm3/cm3 3种情况，进行不同含水率梯度下水分非均匀分布对该仪器测定土壤含水率的影响试验，并在田间试验中进行了实地测试。结果表明，在室内新型时域反射仪随着上下2层土壤含水率梯度差的增加，测定土壤含水率的均方根误差略有增大，在水分分布相对均匀的土壤中测定土壤含水率的均方根误差小于 0.028 cm3/cm3。在田间竖直埋设探头，上湿下干和上干下湿的土壤 相似文献
3.
《Agricultural Water Management》2003,59(3):205-216
The adequate estimation of water content distribution in wetted volume is fundamental in determining the number of drippers per plant and their location below the plant canopy in drip irrigation. Measurements of water content distribution are usually made by opening trenches, which is a time-consuming method and sometimes imprecise. Recent scientific developments have created the possibility of monitoring the soil moisture content using electronic sensors. The objective of this research was to develop and test two multi-wire time domain reflectometry (TDR) probes with electrical impedance discontinuities (referred to as the multi-wire probe) for sensing soil profile water content distribution. The experiment was divided in two parts. In part one, the laboratory performance of two multi-wire probe designs was studied and their reliability to monitor the water content variation in a porous media profile was evaluated. The second part was conducted in a 250 l bucket and the soil water content distribution, for an application depth of 15 mm, was evaluated by monitoring over 6 days at discharge rates of 2 and 4 l h−1. The results demonstrated the viability of using multi-wire probes to estimate soil water content distribution with different probe designs and to consistently obtain water content measurement in water dynamic processes. The following conclusion may drawn from the main results: (1) The measured characteristic impedance of the multi-wire probe for different designs was not the same as that geometrically calculated. This was due to the non-ideal probe geometry which provoked signal loss, thus, hindering peak impedance interpretation, mainly for probe 1 design. (2) The use of multi-wire probes in the TDR equipment showed a speedy determination of soil profile water content distribution using a single measurement. 相似文献
4.
J. G. Annandale N. Z. Jovanovic G. S. Campbell N. Du Sautoy N. Benadé 《Irrigation Science》2003,22(3-4):157-170
Distribution of water and energy is non-uniform in widely spaced, micro-irrigated, hedgerow crops. For accurate water use predictions, this two-dimensional variation in the energy and water balance must be adequately accounted for. To this end, a user-friendly, two-dimensional, mechanistic soil water balance model (SWB-2D), has been developed. Energy is partitioned at the surface depending on solar orientation, row direction and canopy size, shape and leaf area density. Water is assumed to be distributed uniformly at the surface in the case of rainfall, whilst micro-irrigation only wets a limited portion of the field. Crop water uptake is calculated as a function of evaporative demand, soil water potential and root density. Evaporation is also calculated as being either limited by available energy or by water supply. Water is redistributed in the soil in two dimensions with a finite difference solution to the Richards equation. A field trial was set up to test the 2-D soil water balance model in a citrus orchard at Syferkuil (Pietersburg, South Africa). Model predictions generally compared well to actual soil water content measured with time domain reflectometry probes. Scenario modelling and analyses were carried out by varying some input parameters (row orientation, canopy width, wetted diameter and fraction of roots in the wetted volume of soil) and observing variations in the output of the soil water balance. The model holds potential for improving irrigation scheduling and efficiency through increased understanding and accuracy in estimating soil water reserves, since it accounts for the differing conditions in the under-tree irrigated strip and inter-row rainfed areas.Communicated by K. Bristow 相似文献
5.
为探明扶埂开沟膜下灌条件对作物土壤水分分布以及经济效益的影响,以温室番茄为研究对象,采用完全随机试验设计方法,通过时域反射仪进行水分观测,研究扶埂开沟膜下灌条件下土壤水分分布规律,以及该灌溉方式对温室番茄经济效益的影响.结果表明:扶埂开沟膜下灌,垄背的土壤剖面达到最大含水量时间迟于垄沟以及垄坡,垄背剖面观测点在灌水后184 h;在扶埂开沟膜下灌条件下,温室番茄在苗期内进行缺水灌溉的IWUE最大达到34.925 kg/(hm2·mm-1), 产量与商果率均较高,综合产生的净收入最高,经济效益达到最大值. 相似文献
6.
Laboratory and field measurements of soil water content were obtained using gravimetric and Theta-Probe methods, the latter
a frequency-domain reflectometry method. We obtained real-time in situ measurements of soil water content at depths of 30,
80, 160, 240 and 350 mm to evaluate irrigation practice. A datalogger recording the change in soil water content (and cumulative
irrigation) at 20-min intervals was used, with appropriate calculations and graphical presentation, to predict the time and
amount of irrigation water required for soil water content to reach field capacity. Measurements at three instead of five
depths yielded a different depth-averaged soil water content under relatively dry conditions (less than 0.273 m3 m−3), and predicted a later start for irrigation and early crop water stress. Investing in additional sensores for scheduling
irrigation would be compensated by financial resources saved through avoiding excess or deficit irrigation, and the associated
application cost, loss of nutrients and soil due to deep percolation and erosion, and loss of crop production. 相似文献
7.
针对现有监测方式难以大面积准确监测植株个体水分状况,且猕猴桃果园的郁闭性导致根域土壤含水率（Root domain soil water content,RSWC）监测方法匮乏的问题,使用多层感知机（Multi-layer perceptron,MLP）和冠层植被指数来预测果实膨大期（5—9月）徐香猕猴桃植株40cm深度的RSWC。在MLP训练数据的预处理中,采用Pearson相关系数作为输入（植被指数）与输出（RSWC）的相关性评价指标,采用单因素方差分析作为输入与输出的显著性评价指标。进一步考虑冠层采集范围可能对模型精度造成的影响,将数据分割为不同尺度对MLP进行训练评估。结果表明,重归一化植被指数（Renormalized difference vegetation index,RDVI）与RSWC具有最高的相关性与显著性,相关系数和P分别为0.744和0.007,该指数可以作为RSWC反演的输入量。对不同尺度RDVI的建模数据表明,模型精度与RDVI采样面积A及对角线长度L有着较强的相关性（R2分别为0.991和0.993）,为了使模型精度最大化,采样面积应在2.540~3.038m2之间。通过使用该尺度的RDVI建立的MLP模型达到最大精度（R2为0.638,RMSE为0.016）。本研究可为建立非接触性猕猴桃果园土壤含水率估算方法与果园灌溉系统设计提供依据。 相似文献
8.
Eyüp Selim Köksal Süleyman Kodal Yusuf Ersoy Yildirim 《Agricultural Water Management》2010,98(2):353-360
Determination of temporal and spatial distribution of water use (WU) within agricultural land is critical for irrigation management and could be achieved by remotely sensed data. The aim of this study was to estimate WU of dwarf green beans under excessive and limited irrigation water application conditions through indicators based on remotely sensed data. For this purpose, field experiments were conducted comprising of six different irrigation water levels. Soil water content, climatic parameters, canopy temperature and spectral reflectance were all monitored. Reference evapotranspiration (ET0), crop coefficient Kc and potential crop evapotraspiration (ETc) were calculated by means of methods described in FAO-56. In addition, WU values were determined by using soil water balance residual and various indexes were calculated. Water use fraction (WUF), which represents both excessive and limited irrigation applications, was defined through WU, ET0 and Kc. Based on the relationships between WUF and remotely sensed indexes, WU of each irrigation treatments were then estimated. According to comparisons between estimated and measured WU, in general crop water stress index (CWSI) can be offered for monitoring of irrigated land. At the same time, under water stress, correlation between measured WU and estimated WU based on CWSI was the highest too. However, canopy-air temperature difference (Tc − Ta) is more reliable than others for excessive water use conditions. Where there is no data related to canopy temperature, some of spectral vegetation indexes could be preferable in the estimation of WU. 相似文献
9.
无人机遥感技术在精量灌溉中应用的研究进展 总被引：4，自引：0，他引：4
以提高农业用水效率为目标的精量灌溉是未来农业灌溉的主要模式,精量灌溉的前提条件是对作物缺水的精准诊断和科学的灌溉决策。用于作物缺水诊断和灌溉决策定量指标的信息获取技术主要基于田间定点监测、地面车载移动监测及卫星遥感。无人机从根本上解决了卫星遥感由于时空分辨率低而导致的瞬时拓延、空间尺度转换、遥感参数与模型参数定量对应等技术难题,也克服了地面监测效率低、成本高、影响田间作业等问题。近几年的研究结果表明,无人机遥感系统可以高通量地获取多个地块的高时空分辨率图像,使精准分析农业气象条件、土壤条件、作物表型等参数的空间变异性及其相互关系成为可能,为大面积农田范围内快速感知作物缺水空间变异性提供了新手段,在精量灌溉技术应用中具有明显的优势和广阔的前景。无人机遥感系统已经应用在作物覆盖度、株高、倒伏面积、生物量、叶面积指数、冠层温度等农情信息的监测方面,但在作物缺水诊断和灌溉决策定量指标监测方面的研究才刚刚起步,目前主要集中在作物水分胁迫指数(CWSI)、作物系数、冠层结构相关指数、土壤含水率、叶黄素相关指数(PRI)等参数估算的研究,有些指标已经成功应用于监测多种作物的水分胁迫状况,但对于大多数作物和指标,模型的普适性还有待进一步研究。给出了无人机遥感在精准灌溉技术中应用的技术体系,并指出,为满足不同尺度的高效率监测和实现农业用水精准动态管理的需求,今后无人机遥感需要结合卫星遥感和地面监测系统,其中天空地一体化农业水信息监测网络优化布局方法与智能组网技术、多源信息时空融合与同化技术、作物缺水多指标综合诊断模型、农业灌溉大数据等将是未来重点研究内容。 相似文献
10.
为探究西南干热河谷地区典型经济林木橙子树的蒸腾耗水机制,利用热扩散式探针TDP、冠层分析仪、土壤水分传感器TDR、全自动气象站等设备获取橙子树蒸腾量、叶面积指数、土壤含水率和气象因子（气温、辐射、饱和水汽压差、降雨量等）的长期数据。对橙子树蒸腾规律的环境控制和生理调节特征进行系统研究,结果表明：相比于干季和雨季,干热季橙子树表现出较为保守的水分利用机制,日蒸腾量、冠层导度和退耦系数都显著低于其他两个季节。干季和雨季,橙子树蒸腾活动受太阳辐射和饱和水汽压差的交替控制,而干热季蒸腾活动主要受饱和水汽压差的驱动。冠层导度与气象因子日内动态变化特征之间存在时滞效应,且这种效应在不同天气不同季节具有差异。受叶面积指数影响,饱和水汽压差与冠层导度在整个年份呈负对数相关关系,其他环境因子与冠层导度在叶面积指数小于4m2/m2时呈负对数相关关系,大于等于4m2/m2时呈二次函数相关关系。不同环境条件下虽然冠层导度对饱和水汽压差的敏感性不同,但蒸腾耗水在大多数环境条件下基本遵循等水势调节策略,但个别环境条件下存在环境胁迫应对失衡风险。研究结果可为干热河谷区橙子园环境胁迫诊断提供直接依据,有利于灌溉制度的科学优化和节水调控技术体系的高效制定。 相似文献
11.
Application of a new method to evaluate crop water stress index 总被引：1，自引：0，他引：1
Optimum water management and irrigation require timely detection of crop water condition. Usually crop water condition can be indicated by crop water stress index (CWSI), which can be estimated based on the measurements of either soil water or plant status. Estimation of CWSI by canopy temperature is one of them and has the potential to be widely applied because of its quick response and remotely measurable features. To calculate CWSI, the conventional canopy-temperature-based model (Jackson’s model) requires the measurement or estimation of the canopy temperature, the maximum canopy temperature (T
cu), and the minimum canopy temperature (T
cl). Because extensive measurements are necessary to estimate T
cu and T
cl, its application is limited. In this study, by introducing the temperature of an imitation leaf (a leaf without transpiration, T
p) and based on the principles of energy balance, we studied the possibility to replace T
cu by T
p and reduce the included parameters for CWSI calculation. Field experiments were carried out in a winter wheat (Triticum aestivum L.) field in Luancheng area, Hebei Province, the main production area of winter wheat in China. Six irrigation treatments were established and soil water content, leaf water potential, soil evaporation rate, plant transpiration rate, biomass, yield, and regular meteorological variables of each treatment were measured. Results indicate that the values of T
cu agree with the values of T
p with a regression coefficient r=0.988. While the values of CWSI estimated by the use of T
p are in agreement with CWSI by Jackson’s method, with a regression coefficient r=0.999. Furthermore, CWSI estimated by the use of T
p has good relations with soil water content and leaf water potential, showing that the estimated CWSI by T
p is a good indicator of soil water and plant status. Therefore, it is concluded that T
cu can be replaced by T
p and the included parameters for CWSI calculation can be significantly reduced by this replacement. 相似文献
12.
【目的】建立1种适用于不同水分条件的棉田氮肥高光谱监测模型。【方法】通过设置包含灌溉梯度和施氮梯度的大田水肥试验,在生育期内同步测定棉花冠层光谱反射率、冠层含氮量(Canopy nitrogen content, CNC)、冠层等效水厚度(Canopy equivalent water thickness, CEWT)等信息,综合分析棉花冠层含氮量及冠层等效水厚度与光谱指数的相关性,确定最优光谱指数并构建棉花CNC的高光谱监测模型。【结果】冠层光谱与CNC在可见光波段附近出现连续的敏感区域,其中最大相关系数|r|max为0.53,位于718nm;在不考虑CEWT对模型精度影响时,NDSI(800,770)的建模效果最佳(R^2=0.76),但是进入花铃后期其预测精度偏低,出现了低估现象;综合考虑CEWT的影响后,本研究选取NDSI(570,500)作为最优光谱指数,所建模型有效改善了棉花含水率变化而造成模型精度偏低的现象(RRMSE=0.18)。【结论】本研究建立的新型水分钝感光谱指数NDSI(570,500)可以有效提升棉花CNC的估算精度,为高光谱技术在棉田氮肥监测的应用提供技术依据。 相似文献
13.
Summary A field study was conducted on cotton (Gossypium hirsutum L. c.v. Acala SJ-2) to investigate the effects of soil salinity on the responses of stress indices derived from canopy temperature, leaf diffusion resistance and leaf water potential. The four salinity treatments used in this study were obtained by mixtures of aqueduct and well water to provide mean soil water electrical conductivities of 17, 27, 32 and 38 dS/m in the upper 0.6 m of soil profile. The study was conducted on a sandy loam saline-alkali soil in the lower San Joaquin Valley of California on 30 July 1981, when the soil profile was adequately irrigated to remove any interference of soil matric potential on the stress measurements. Measurements of canopy temperature, leaf water potential and leaf diffusion resistance were made hourly throughout the day.Crop water stress index (CWSI) estimates derived from canopy temperature measurements in the least saline treatment had values similar to those found for cotton grown under minimum salinity profiles. Throughout the course of the day the treatments affected CWSI values with the maximum differences occurring in mid-afternoon. Salinity induced differences were also evident in the leaf diffusion resistance and leaf water potential measurements. Vapor pressure deficit was found to indicate the evaporative demand at which cotton could maintain potential water use for the various soil salinity levels studied. At vapor pressure deficits greater than 5 kPa, cotton would appear stressed at in situ soil water electrical conductivities exceeding 15 dS/m. The CWSI was as sensitive to osmotic stress as other, more traditional plant measures, provided a broader spatial resolution and appeared to be a practical tool for assessing osmotic stress occurring within irrigated cotton fields. 相似文献
14.
无人机热红外反演土壤含水率的方法 总被引：1，自引：0，他引：1
以不同生育期夏玉米为对象,讨论无人机热红外反演夏玉米田土壤含水率的精度及反演方法.利用无人机获取试验区的可见光和热红外图像.通过可见光图像提取冠层掩膜并叠加在热红外图像上提取玉米冠层温度,分析冠层温度的变化趋势及与叶面积指数(LAI)的相关性.最后,利用冠气温差的相反数与叶面积指数构建了一个新指标(DTL),讨论了冠气温差或DTL指标反演土壤含水率的准确性.结果表明:冠层温度随着土壤含水量的增加而降低,夏玉米LAI在一定程度上可以表征冠层温度;对比4个时期的数据,发现冠气温差反演效果在灌溉后较好(如2次灌后R2分别为0.614 6和0.463 7);与冠气温差相比,DTL指标可以提高土壤含水量反演的精度,如0~20 cm深度的R2从0.614 6和0.463 7提高到0.661 6和0.485 0.该研究对热红外反演夏玉米田间土壤含水率方法进行了新的尝试. 相似文献
15.
Canopy temperature as a measure of salinity stress on sorghum 总被引：1，自引：0，他引：1
Summary A complete understanding of plant response to combined water and salinity stress is desirable. Previous growth chamber and greenhouse experiments with sorghum and maize indicate that soil salinity, by negatively affecting growth processes, may reduce consumptive water use, thus prolonging the supply of available soil moisture. In the present field experiment, canopy temperature measurements were used to examine the effect of soil salinity on the plant-soil water relations of sorghum (Sorghum bicolor L. cv. Northrup King 1580). An infrared thermometer was used to measure canopy temperature during a 9-day period including two irrigations in plots of various salinities. The salinity treatments were created by a dual line-source sprinkler irrigation system, which applied waters of different quality. Excess irrigation allowed soil moisture to be uniform across the salinity treatments at the beginning of the measurement period. Consumptive water use and soil salinity were measured to quantify the salinity and water treatments. Grain and dry matter yields provided measures of plant response. Canopy temperature measurements were sensitive enough to detect differences across the salinity treatments when soil moisture was uniform for several days following irrigation. However, over the 9-day measurement period, plants in the low-salt plots used more water than plants in the high-salt plots. This differential water use eventually offset the salinity-induced stress, with the result that temperature differences were eliminated. Differences in temperature were observed again following irrigation. The results demonstrate that canopy temperature can be used as a tool to detect salinity stress on sorghum. Timing of measurements with regard to irrigation is identified as a key factor in detecting temperature differences that can be attributed to the presence of soil salinity. 相似文献
16.
干旱是影响农业生产的主要气候因素。传统的农业干旱监测主要是基于气象和水文数据,虽然能提供监测点上较为精确的干旱监测结果,但是在监测面上的农业干旱时,仍存在一定的局限。遥感技术的快速发展,尤其是目前在轨的卫星传感器感测的电磁波段涵盖了可见光、近红外、热红外和微波等波段,为区域尺度农业干旱监测提供了新的手段。充分利用卫星遥感数据获得的丰富地表信息进行农业干旱监测和预测具有重要的研究意义。本文从遥感指数方法、土壤含水量方法和作物需水量方法三个方面阐述了基于卫星遥感的农业干旱监测研究进展。农业干旱预测是在干旱监测的基础上进行时间轴的预测,本文在总结干旱监测进展的基础上,进一步简述了以干旱指数方法和作物生长模型方法为主的农业干旱预测研究进展。 相似文献
17.
《Agricultural Water Management》2004,65(1):21-38
Quantifying the soil water deficit (SWD) and its relation to canopy or leaf conductance is essential for application of the Penman–Monteith equation to water-stressed plants. As the water uptake of a single root depends on the water content of the soil in its immediate vicinity, the non-uniform distribution of water and roots in the soil profile does not allow simple quantification of SWD from soil-based measurements. Using measurements of stem sap flux (with a heat pulse technique), soil evaporation (with micro-lysimeters) and meteorological parameters the canopy conductance was obtained through inversion of the Penman–Monteith equation. SWD was evaluated by averaging the soil water content profile of the root zone (monitored by layers with the TDR sensors) weighted by root distribution of the layers. The average canopy conductance at midday (11:00–15:00, Israel Summer Time), denoted as Gnoon, was computed for each day of the experimental period. Stable summer weather, typical of the Mediterranean region, and the fully developed crop canopy, made water stress the only plausible cause of a Gnoon decline. However, the daily decline of Gnoon did not occur at the same weighted average soil water content during the successive drying cycles. For the cycle with less irrigation, the decline in Gnoon occurred at higher soil moisture levels. Alternatively, when SWD was determined from the water balance, i.e., by defining water deficit as irrigation minus accumulated evapotranspiration, the Gnoon decline occurred at the same value of water deficit for all irrigation cycles. We conclude that a climate-based soil water balance model is a better means of quantifying SWD than a solely soil-based measurement. 相似文献
18.
作物冠层温度是反映作物水分状况的一个良好指标，在研究环境因素对冠层温度影响的基础上，分析了不同土壤水分条件下棉花冠层温度的变化规律。研究表明了冠层温度与细胞液浓度之间存在良好关系，建立的冠层温度与气温差同气象因素和土壤水分的关系可用于判断作物的缺水状况 相似文献
19.
Accurate irrigation scheduling is important to ensure maximum yield and optimal water use in irrigated cotton. This study
hypothesizes that cotton water stress in relatively humid areas can be detected from crop stress indices derived from canopy
reflectance or temperature. Field experiments were conducted in the 2003 and 2004 crop seasons with three irrigation treatments
and multiple cultivars to study cotton response to water stress. The experiment plots were monitored for soil water potential
(SWP), canopy reflectance and canopy temperature. Four crop stress indices namely normalized difference vegetative index (NDVI),
green NDVI (GNDVI), stress time (ST) index and crop water stress index (CWSI) were evaluated for their ability to indicate
water stress. These indices were analyzed with classic mixed regression models and spatial regression models for split-plot
design. Rainfall was plentiful in both seasons, providing conditions representative of irrigated agriculture in relatively
wet regions. Under such wet weather conditions, excessive irrigation decreased lint yield, indicating the necessity for accurate
irrigation scheduling. The four crop stress indices showed significant responses to irrigation treatments and strong correlation
to SWP at shallow (0.2 m) depth. Spatial regression models were able to accurately explain the effect of irrigation treatment,
while classic split-plot ANOVA models were confounded by collinearity in data across space and time. The results also verified
that extreme humidity can mask canopy temperature differences with respect to ambient temperature, adding errors to canopy
temperature-based stress indicators.
相似文献
| Sreekala G. BajwaEmail: |
20.
为研究冻融过程对FDR测量土壤体积含水量的影响,采用基于FDR技术的土壤水分传感器TDR-3,通过室内温度实验箱控制环境温度范围为-20～20 ℃,对冻融过程中黏性土样体积含水量进行了测试分析．结果表明:采用FDR测量黏性土样体积含水量,在土样未进行冻融前,温度在0 ℃以上时,FDR的测量值随温度呈线性变化,随着温度的升高而增大,随着温度的降低而减小;黏性土样冻融过程中,在冻结过程中,FDR的测量值随着温度的降低逐渐减小;在融化过程中,随着温度的升高,FDR的测量值逐渐增大;相同温度条件下,黏性土冻结过程中FDR的测量值明显大于黏性土融化过程中FDR的测量值,0℃时两者差值最大,该差值受土壤初始体积含水量和冻融温度的影响．研究成果对于提高FDR测量冻融过程中土壤体积含水量的可靠性具有重要意义． 相似文献