Evaluation of radiant canopy temperature and soil water measurement for quantifying the contribution of shallow watertables to crop evaporation.

Soil Research ◽  
1990 ◽  
Vol 28 (6) ◽  
pp. 1013 ◽  
Author(s):  
L Mateos ◽  
WS Meyer ◽  
RCG Smith ◽  
R Sides
Keyword(s):  
Heat Flux ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Aerodynamic Resistance ◽  
Sensible Heat Flux ◽  
Canopy Temperature ◽  
Balance Model ◽  
Accurate Estimation ◽  
Clay Loam

Accurate estimation of the contribution of shallow watertables to crop water consumption is of major importance for improved irrigation practice and watertable management. A water balance model based on radiant canopy temperature estimations of crop evaporation and measurements of the change in the soil water content with a neutron probe was used to estimate the net upward flux from the watertable. The model was tested against measurements made by using two weighing lysimeters containing loam and clay loam soils, and the estimation of errors involved was analysed. The watertable in the lysimeters was maintained 1 m below the ground surface. Evaporation from a soybean crop was estimated by using an energy balance model with measured values of net radiant energy and soil heat flux. Sensible heat flux was calculated from the difference between the radiant canopy temperature and air temperature, together with an estimated aerodynamic resistance of the crop. Two sources of error were associated with the model, one due to the estimation of crop evaporation and the other due to the measurement of the change in soil water content. Errors of 0.7 and 5.1 mm per day were estimated for the first and second sources respectively. The accuracy of the method was determined by the length of the period considered and by the contribution of the watertable itself. An error of 20% was estimated when periods of 20 and 80 days were considered in the loam and clay loam soils respectively. Shorter time periods will result in larger uncertainty. The implications of the these results for watertable management are discussed.

Calibration and evaluation of a capacitance probe in agricultural soils in northeast Brazil

2020 ◽  
Author(s):  
Ceres Duarte Guedes Cabral de Almeida ◽  
Lais Barreto Franco ◽  
José Ediclécio Barbosa dos Santos ◽  
Brivaldo Gomes de Almeida ◽  
Giuseppe Provenzano
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Agricultural Soils ◽  
Irrigation Management ◽  
Clay Loam ◽  
Sandy Clay Loam ◽  
Sandy Clay ◽  
Disturbed Soil ◽  
Capacitance Probe

<p>Soil water content is an important parameter for irrigation management. Among the indirect methods to determine soil water content (SWC), there are electronic sensors, that need site-specific calibration to increase the accuracy of the measurements. In this research, a capacitance probe (Diviner 2000®, Sentek Pty Ltda., Australia) was calibrated for two agricultural soils. The experiment was carried out in a protected environment at the Federal Rural University of Pernambuco (UFRPE), Brazil. The textural classes of soils were sandy clay loam (66% sand) and sandy (95% sand). Undisturbed and disturbed soil samples were collected in the soil top layer (0-30 cm). The disturbed soil samples were initially air-dried, passed through a 4.75 mm mesh sieve, and then introduced to fill eight vessels (four replications for each soil). These vessels, equipped with drainage holes, have lower and upper diameters of 15 cm and 25 cm, respectively, and height of 22.5 cm (4.66 L). In each pot, a 5 cm layer of gravel with an average diameter of 2 cm covered with bidim® geotextile was disposed before introducing the soil. During filling, the soil was compacted to reach the same bulk density measured on the undisturbed samples (sandy clay loam: 1.54 g cm<sup>-3</sup> and sandy: 1.50 g cm<sup>-3</sup>). In the center of each pot, a PVC access tube was installed. According to the manufacturer's recommendation, during calibration, the probe normalization was performed. The pots were wetted by capillary rise and, once saturated, they were placed on a bench for drainage. After this process stopped each pot was daily weighed at a fixed time (8 a.m.), and the sensor reading was acquired until when the daily mass variations became negligible. Data were used for regression analysis to fit the site-specific calibration equation and to evaluate the mean error. Linear calibration equations, characterized by R<sup>2</sup>=0.931 and 0.986, were obtained for the sandy clay loam and the sandy soil, respectively. The mean errors (ME) associated with the manufacturer’s equation resulted in -0.05 and -0.01 for sandy clay loam and for sandy soil and decreased after calibration. The results confirmed the suitability of the manufacturer's equation in sandy soils. On the other hand, the manufacture’s equation slightly underestimated SWC, in sandy clay loam soil, especially in the range above 0.26 m<sup>3</sup> m<sup>-3</sup>. The Diviner 2000 probe can be therefore successfully used to support irrigation management in irrigated areas with soils similar to those investigated because it is easy to operate and allows fairly accurate estimations of soil water content.</p>

scholarly journals Penerapan Zero Runoff System (ZROS) dan Efektivitas Penurunan Limpasan Permukaan Pada Lahan Miring di DAS Cidanau, Banten

2017 ◽  
Vol 23 (2) ◽  
pp. 102 ◽  
Author(s):  
Yanuar Chandra Wirasembada ◽  
Budi Indra Setiawan ◽  
Satyanto Krido Saptomo
Keyword(s):  
Water Balance ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Water Conservation ◽  
Water Balance Model ◽  
Balance Model ◽  
Coefficient Of Determination ◽  
Before And After ◽  
Zero Runoff

Runoff is one of flood and erosion causal factor in Indonesia. Runoff occurred when rainfall cannot be infiltrated and flowed on the ground surface. Cidanau watershed has quite high rainfall average (2573 mm/year) so it has high runoff potential. Zero Runoff System (ZROS) is one of water conservation way which can infiltrate runoff to the ground using permeation structures. ZROS’s successful parameter in order to decreasing runoff rate can be observed by the soil water content differences before and after ZROS application. Soil water content estimation was conducted by water balance model with and without runoff and then it is compared with soil water content from measuring. The simulation results indicated that soil water content in the research field before and after ZROS application is 0.476 and 0.569 m3/m3 respectively. The simulation is also conducted for past 10 years (2004-2013) and resulted higher soil water content if ZROS were applied. This results indicates that ZROS capable to decrease and permeate runoff to the ground and then increase soil water content level. Water balance model with and without runoff has coefficient of determination (R2) 0.606. It means that this model could simulate the soil water content differences before and after ZROS application valid relatively.

Forecasting wheat yields using a water budgeting model

1989 ◽  
Vol 40 (4) ◽  
pp. 715 ◽  
Author(s):  
I Cordery ◽  
AG Graham
Keyword(s):  
Water Balance ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
New South ◽  
Meteorological Data ◽  
New South Wales ◽  
Balance Model ◽  
Soil Layers ◽  
South Wales

A model has been developed to forecast soil water variations and wheat crop growth in dry land situations. The forecast of the yield to be expected if sowing occurred today is obtained by running the calibrated model for all years for which meteorological data are available. The soil water content on today's date in each year is fixed at today's observed soil water value. From each year of observed meteorological data, an estimate is made of the yield. These yield data allow construction of a frequency distribution of yield which can be used to make a probabilistic forecast. The model involves two sub-models, a water balance model and acrop development model. The two sub-models interact to provide 5-day estimates of soil water content, actual evaporation and transpiration, runoff and increments to biomass and grain yield. The water balance model takes inputs of daily rainfall and estimated potential evapotranspiration. Available energy is partitioned between evaporation and transpiration depending on leaf area index. There are two soil layers plus a surface interception and depression store. Water removal from the soil layers is dependent on root development and the location of available water. Biomass production is driven by actual transpiration and transpiration efficiency and so biomass and grain development are dependent on the timing and amount of water and energy utilization by the crop. The model was first calibrated in northern New South Wales with 13 years of research station data. With minor recalibration, it provided good estimates of observed district wheat harvests for a continuous period of 75 years. Further recalibration with 30 years of shire data from Queensland, 29 years of single farm data in southern New South Wales and with 31 years of county data from northwestern USA., indicated the model is able to accurately reproduce observed yields and has the potential to provide reliable forecasts of yield, in a range of different climates.

scholarly journals Predicting Soil Water Content on Rainfed Maize through Aerial Thermal Imaging

2021 ◽  
Vol 3 (4) ◽  
pp. 942-953
Author(s):  
Matheus Gabriel Acorsi ◽  
Leandro Maria Gimenez
Keyword(s):  
Linear Regression ◽  
Spatial Variability ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Water Status ◽  
Canopy Temperature ◽  
Crop Water ◽  
Soil Water Status ◽  
Physical Attributes

Restrictions on soil water supply can dramatically reduce crop yields by affecting the growth and development of plants. For this reason, screening tools that can detect crop water stress early have been long investigated, with canopy temperature (CT) being widely used for this purpose. In this study, we investigated the relationship between canopy temperature retrieved from unmanned aerial vehicles (UAV) based thermal imagery with soil and plant attributes, using a rainfed maize field as the area of study. The flight mission was conducted during the late vegetative stage and at solar noon, when a considerable soil water deficit was detected according to the soil water balance model used. While the images were being taken, soil sampling was conducted to determine the soil water content across the field. The sampling results demonstrated the spatial variability of soil water status, with soil volumetric water content (SVWC) presenting 10.4% of variation and values close to the permanent wilting point (PWP), reflecting CT readings that ranged from 32.8 to 40.6 °C among the sampling locations. Although CT correlated well with many of the physical attributes of soil that are related to water dynamics, the simple linear regression between CT and soil water content variables yielded coefficients of determination (R2) = 0.42, indicating that CT alone might not be sufficient to predict soil water status. Nonetheless, when CT was combined with some soil physical attributes in a multiple linear regression, the prediction capacity was significantly increased, achieving an R2 value = 0.88. This result indicates the potential use of CT along with certain soil physical variables to predict crop water status, making it a useful tool for studies exploring the spatial variability of in-season drought stress.

scholarly journals 429 Detecting Incipient Water Stress in Buffalograss and Kentucky Bluegrass through Foliage Temperature using Lowcost Infrared Sensors

HortScience ◽  
2000 ◽  
Vol 35 (3) ◽  
pp. 467C-467
Author(s):  
J. Ryan Stewart ◽  
Roger Kjelgren
Keyword(s):  
Water Stress ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Poa Pratensis ◽  
Warm Season ◽  
Canopy Temperature ◽  
Kentucky Bluegrass ◽  
Infrared Sensors ◽  
Drought Avoidance

Infrared sensors were used to quantify canopy temperature and thus detect differences in incipient water stress between a cool-season grass [Kentucky bluegrass (KBG) (Poa pratensis)] and a warm-season grass [buffalograss (BG) (Buchloe dactyloides)]. The infrared sensors, connected to a datalogger, measured average hourly leaf–air temperatures (TL–TA) 1 m above eight replicate plots of Kentucky bluegrass and eight replicate plots of buffalograss. Air temperature and relative humidity from a nearby weather station were used to calculate the average hourly vapor pressure deficit (VPD). In late July, we ceased irrigating and measured TL–TA and soil water content while allowing the turf to dry down for 5 weeks. Soil water content was measured with a neutron probe. Both species exhibited a significant relationship between TL–TA and VPD. As the VPD increased, TL–TA decreased in both species (KBG r2 = 0.73, BG r2 = 0.71) on the 2nd day after an irrigation during well-watered conditions. An artifact was created on the first day after an irrigation as a result of excessive surface evaporation. KBG and BG were similar under well-watered conditions. KBG had a higher TL–TA after 4 to 5 days without irrigation. By contrast, BG did not have a higher TL–TA until 25 to 30 days without irrigation. Part of BG's drought avoidance was extraction of soil water down to 0.9 m vs. 0.45 m for KBG.

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