Determining Crop and Pan Coefficients for Cauliflower and Red Cabbage Crops Under Cool Season Semiarid Climatic Conditions

The aim of this study was to estimate the evapotranspiration of cauliflower and red cabbage crops grown under cool season semiarid climatic conditions from Class A pan evaporation. Actual evapotranspiration （ETc） of cauliflower and red cabbage crops was calculated according to the water balance approach. Reference evapotranspiration （ETo） was calculated with FAO Penman-Monteith equation. Pan evaporation （Epan） was measured by using Class A pan. Seasonal ETc was determined as 475 mm for cauliflower and 556 nun for red cabbage. Seasonal pan coefficient （kp=ETo/Epan） was determined as 0.82, and the seasonal crop coefficient （kc=ETc/ETo） was determined as 0.84 for cauliflower and 0.83 for red cabbage. So the evapotranspiration of cauliflower and red cabbage crops was estimated as 70% Class A pan evaporation.

Evaluation of Actual Evapotranspiration and Crop Coefficient in Carrot by Remote Sensing Methodology Using Drainage and River Water to Overcome Reduced Water Availability

Searching for alternative methods for traditional irrigation is World trend at days due to a reduction in water and increased of drought due to climate changes therefore farmers need use modern methods of scheduling water and minimizing water losses while also increasing yield. To meet the future increasing demands water and food there is a need to utilize alternative methods to reduce evaporation, transpiration and deep percolation of water. Any countries use recycled water (drain and sewage) and desalination water from the sea or drains to irrigate crops plus computing actual crop evapotranspiration (ETc) so as to calculate the amount of water to apply to a crop. The paper aims to assess the actual evaporation and evaporation coefficient of carrots, by planting carrots in a field and the crop was exposed to several sources of water (DW and RW) and comparing ETc, Kc and production among plots of three sites (A, B and C). The study used two types of irrigation water (drain water (DW) and river water (RW)). The results were to monthly rate and accumulated actual evapotranspiration to C (irrigation by RW only) more than A (67% RW and 33% DW) and B (17% RW and 83% DW) via 7% and 58%, respectively. The yield to C more than A and B by 17% and 75%, respectively. In conclusion the use of DW can cause a reduction in crop consumptive of carrot crops also causes a reduction in yield, crop length, root length, root size, canopy of crop, number of leaves and biomass of the plant therefore, the drainage water needs to treated before irrigating crops And making use of it to irrigate the fields and fill the shortfall in the amount of water from the river. The drain water helped on filling the water shortage due to climate changes and giving production of carrot crop but less than river water.

Estimating Crop Coefficient in Intermittent Irrigation Paddy Fields Using Excel Solver

The current study proposes a novel method using Excel Solver to estimate, from limited data, crop coefficient （Kc） in paddy fields under intermittent irrigation （11）. The proposed method was examined in a field experiment conducted at Karang Sari Village, Bekasi, West Java, Indonesia during the first rice season of 2007/2008 （December 2007 to April 2008） in the rainy season. As the control, continuous flooding irrigation （CF） was applied to the conventional rice cultivation fields. Based on the observed water storage, Excel Solver was used to estimate crop evapotranspiration. Estimated crop evapotranspiration was used to compute Kc value, then the average Kc values at each growth stage were compared with that for the CF treatment. The estimation method was evaluated by comparing estimated crop evapotranspiration and the crop evapotranspiration derived by the well established FAO procedure. Excel Solver estimated crop evapotranspiration accurately with R2 values higher than 0.81. Accordingly, more than 81% of the FAO crop evapotranspiration was described by the proposed method. Thus, Kc value could be well determined from those estimated crop evapotranspiration. Under the II treatment, the average Kc values were 0.70, 1.06, 1.24 and 1：22 for the initial, crop development, reproductive and late stages, respectively. These values were lower than those under the CF treatment for initial and crop development stages because of a minimal soil evaporation and intense dryness during these stages. However, average Kc values under the II treatment were higher than those under the CF treatment at the reproductive and late stages, indicating that the II treatment promoted more plant activity particularly for dry biomass production as indicated by a greater number of tillers per hill.

Seasonal variation of evapotranspiration,Priestley-Taylor coefficient and crop coefficient in diverse landscapes

Priestley-Taylor equation(PT)and the Penman-Monteith equation(PM)are commonly used methods for regional evapotranspiration monitoring,using the PT coefficient(α_(a))and PM crop/vegetation coefficient(K_(c)).This paper investigates the seasonal changes inα_(a)and K_(c)at five sites in Australia and China,to understand the relation-ship between environmental conditions and evapotranspiration when applying different evaporation estimation methods.The research shows that higher actual evapotranspiration does not lead to higherα_(a)and K_(c)values.α_(a)and K_(c)perform similarly in cropland and forest environments in both China and Australia.Bothα_(a)and K_(c)continuously increase to a peak during the growing season and then decrease to their lowest values during the winter season.Considering K_(c)’s similar performance toα_(a)and its greater data processing requirements,K_(c)has few advantages for estimating regional evapotranspiration.Applying the Priestley-Taylor equation with a regional𝛼indicator will enhance the accuracy and reduce the workload when estimating regional evapotranspiration for similar landcover types based on remote sensing.

Assessing Crop Water Demand and Deficit for the Growth of Spring Highland Barley in Tibet, China

The aim of this study was to assess the crop water demand and deficit of spring highland barley and discuss suitable irrigation systems for different regions in Tibet, China. Long-term trends in reference crop evapotranspiration and crop water demand were analyzed in different regions, together with crop water demand and deficit of spring highland barley under different precipitation frequencies. Results showed that precipitation trends during growth stages did not benefit the growth of spring highland barley. The crop coefficient of spring highland barley in Tibet was 0.87 and crop water demand was 389.0 ram. In general, a water deficit was found in Tibet, because precipitation was lower than water consumption of spring highland barley. The most severe water deficit were in the jointing to heading stage and the heading to wax ripeness stage, which are the most important growth stages for spring highland barley; water deficit in these two stages would be harmful to the yield. Water deficit showed different characteristics in different regions. In conclusion, irrigation systems may be more successful if based on an analysis of water deficit within different growth stages and in different regions.

Calculation and Simulation of Evapotranspiration of Applied Water

The University of California, Davis and the California Department of Water Resources have developed a weather generator application program “SIMETAW” to simulate weather data from climatic records and to estimate reference evapotranspiration （ETo） and crop evapotranspiration （ETc） with the generated simulation data or with observed data. A database of default soil depth and water holding characteristics, effective crop rooting depths, and crop coefficient （Kc） values to convert ETo to ETc are input into the program. After calculating daily ETc, the input and derived data are used to determine effective rainfall and to generate hypothetical irrigation schedules to estimate the seasonal and annual evapotranspiration of applied water （ETaw）, where ETaw is the net amount of irrigation water needed to produce a crop. in this paper, we will discuss the simulation model and how it determines ETaw for use in water resources planning.

California Simulation of Evapotranspiration of Applied Water and Agricultural Energy Use in California

The California Simulation of Evapotranspiration of Applied Water （CaI-SIMETAW） model is a new tool developed by the California Department of Water Resources and the University of California, Davis to perform daily soil water balance and determine crop evapotranspiration （ETo）, evapotranspiration of applied water （ETaw）, and applied water （AW） for use in California water resources planning. ETaw is a seasonal estimate of the water needed to irrigate a crop assuming 100% irrigation efficiency. The model accounts for soils, crop coefficients, rooting depths, seepage, etc. that influence crop water balance. It provides spatial soil and climate information and it uses historical crop and land-use category information to provide seasonal water balance estimates by combinations of detailed analysis unit and county （DAU/County） over Califomia. The result is a large data base of ETc and ETaw that will be used to update information in the new California Water Plan （CWP）. The application uses the daily climate data, i.e., maximum （Tx） and minimum （Tn） temperature and precipitation （Pcp）, which were derived from monthly USDA-NRCS PRISM data （PRISM Group 2011） and daily US National Climate Data Center （NCDC） climate station data to cover California on a 4 kmx4 km change grid spacing. The application uses daily weather data to determine reference evapotranspiration （ETo）, using the Hargreaves-Samani （HS） equation （Hargreaves and Samani 1982, 1985）. Because the HS equation is based on temperature only, ETo from the HS equation were compared with CIMIS ETo at the same locations using available CIMIS data to determine correction factors to estimate CIMIS ETo from the HS ETo to account for spatial climate differences. CaI-SIMETAW also employs near real-time reference evapotranspiration （ETo） information from Spatial CIMIS, which is a model that combines weather station data and remote sensing to provide a grid of ETo information. A second database containing the available soil water holding capacity and soil depth information for all of California was also developed from the USDA-NRCS SSURGO database. The Cal-SIMETAW program also has the ability to generate daily weather data from monthly mean values for use in studying climate change scenarios and their possible impacts on water demand in the state. The key objective of this project is to improve the accuracy of water use estimates for the California Water Plan （CWP）, which provides a comprehensive report on water supply, demand, and management in California. In this paper, we will discuss the model and how it determines ETaw for use in water resources planning.

Estimating daily actual evapotranspiration of a rice–wheat rotation system in typical farmland in the Huai River Basin using a two-step model and two one-step models

The objective of this study is to evaluate the performance of three models for estimating daily evapotranspiration(ET) by employing flux observation data from three years(2007, 2008 and 2009) during the growing seasons of winter wheat and rice crops cultivated in a farmland ecosystem(Shouxian County) located in the Huai River Basin(HRB), China. The first model is a two-step model(PM-Kc);the other two are one-step models(e.g., Rana-Katerji(R-K) and advection-aridity(AA)). The results showed that the energy closure degrees of eddy covariance(EC) data during winter wheat and rice-growing seasons were reasonable in the HRB, with values ranging from 0.84 to 0.91 and R2 of approximately 0.80. Daily ET of winter wheat showed a slow decreasing trend followed by a rapid increase, while that of rice presented a decreasing trend after an increase. After calibrating the crop coefficient(Kc), the PM–Kc model performed better than the model using the Kc recommended by the Food and Agricultural Organization(FAO). The calibrated key parameters of the R-K model and AA model showed better universality. After calibration, the simulation performance of the PM-Kc model was satisfactory. Both the R-K model and AA model underestimated the daily ET of winter wheat and rice. Compared with that of the R-K model, the simulation result of the AA model was better, especially in the simulation of daily ET of rice. Overall, this research highlighted the consistency of the PM-Kc model to estimate the water demand for rice and wheat crops in the HRB and in similar climatic regions in the world.

Effect of Irrigation Method and Non-Uniformity of Irrigation on Potato Performance and Quality

Potato growth, yield, and quality under improved irrigation methods and non-uniformity of their irrigation applications are important to enhance water management in arid regions. A field experiment was conducted in 2014 spring and fall growing seasons using potato (Solanum tuberosum) grown in northern Egypt at Shibin El Kom, Menofia, Egypt to evaluate potato response to furrow or trickle irrigation. A Randomized Split-Plot Design with irrigation method randomly distributed and non-uniformity of irrigation applications evaluated along either irrigation furrow or trickle lateral as dependent variables measured at the 3rd, 13th, 23rd, 33rd, 43rd and 53rd m along the 55 m irrigation line. Traditional (TF) and partial (PF) furrows as well as trickle point (TP) and line (TL) sources were used as irrigation methods. Each treatment was repeated three times. For a 33rd m treatment, seasonal optimum water use by potato was 328, 234, 269 and 292 mm over 118 days in spring and 200, 164, 178 and 186 mm over 122 days in fall under TF, PF, TP and TL irrigation methods, respectively. Potato tuber yield and quality were significantly affected by growing season (S), irrigation method (I) and non-uniformity of irrigation application (U). Tuber yield, total soluble solid (TSS) and leaf area index (LAI) were significantly affected by I and U, and their interaction I * U;harvest index (HI) was not affected by I but U. Except for TSS by S * I and HI by U * I and S * I, results showed no significant differences. Moreover, tuber weight, number and marketable yield were significantly affected by S, I, U and I * U interaction, except medium tuber size and culls by S. A given 33rd treatment under partial furrow and trickle irrigation, relative to that of traditional furrow, enhanced tuber yield and improved quality in both growing seasons. In non-un- iform irrigation application over two growing seasons, potato crop response was developed under varied irrigation methods. Tuber yields were significantly affected in a linear relationship (r2 ≥ 0.75) by either water deficit or excessive water under irrigation methods.

Determination of Young Olive-Tree Water Consumption with Drainage Lysimeters

Information about olive-tree irrigation in sub-humid climates, as in Uruguay, is scarce. Water consumption of young olive trees, Arbequina variety, was measured for two years with six drainage lysimeters, protected from rain by an automatic rain-out shelter. Irrigation water volume and drainage of each lysimeter were measured daily and soil moisture was registered twice a week with neutron probe at four depths. Evapotranspiration (ETc) was calculated by volume balance. Data periods when available water descended below 50% or increased over 100% were eliminated, as those in which the stem water potential was below -1.5 MPa. Water consumption values were averaged within 7- to 14-day periods, expressed in mm·d-1, and referred to a 2.5 × 5.5 m plantation framework without vegetation cover. There was a positive linear relation of the summer crop coefficient (Kc mid) with age, canopy cover percentage and canopy volume. Canopy cover percentage was the parameter which explained most of the variation of Kc mid, which ranged between 0.13 and 0.24, with 5% and 46% canopy cover, respectively. Full irrigation, associated to a good drainage resulted in a rapid growth of the young plants, bringing forward the start of full production period. This represents useful information for the adjustment of irrigation in olive-tree orchards, to accelerate growth with a rational and sustainable use of both water and energy in Uruguay.

Lysimeter based crop coefficients for estimation of crop evapotranspiration of black gram (Vigna Mungo L.) in sub-humid region

Black gram is dominant pulse crop of the region.Crop coefficient is an important parameter,which needs to be determined for accurate estimates of the crop water requirement.Crop coefficient,the ratio of potential crop evapotranspiration to reference evapotranspiration,is an important parameter in irrigation planning and management.However,this information is not available for many important crops in the study region.A study was undertaken to develop crop coefficients for black gram crop,and a comparison is made of single and dual crop coefficient approaches to estimate actual crop evapotranspiration under the climatic conditions of Udaipur,India.Crop coefficient was developed from daily measured black gram evapotranspiration(ETBG)data by electronic weighing lysimeter and reference evapotranspiration calculated using standard Penman-Monteith method.The measured values of crop coefficient for the crop were 0.48,1.18 and 0.33 during initial,mid-season and late-season stages.The evaluation of different approaches showed that daily ETBG estimate based on dual crop coefficient method have been found best(SE=0.40,r=0.96).Furthermore,a quadratic curve(second-order polynomial)method were fitted well(SE=0.47,r=0.94)to predict crop coefficient values as function of days after sowing(DAS).These locally developed and evaluated values can be used for proper irrigation planning in water scarcity area of Udaipur and other areas with similar agro-ecological conditions.

Evaluation of dual crop coefficient approach on evapotranspiration calculation of cherry trees

A simple way to estimate tree evapotranspiration is needed for orchard irrigation schedules and water management practice,and the dual crop coefficient(DCC)approach provides such a method.Plot experiments on cherry trees were conducted in an orchard of Beijing,China,from 2011 to 2013,to test the suitability and reliability of the DCC method.The calculated results from the DCC method were compared with those directly measured by water balance(WB)and sap flow(SF)methods.Results showed that total evapotranspiration in the whole growth period of cherry trees obtained by WB,SF and DCC methods was 560.0-569.3 mm,544.7-569.8 mm and 564.1-574.6 mm,respectively.The Nash-Sutcliffe efficiency(NSE)and the ratio of root-mean-square error to the standard deviation of measured data(RSR)showed that the calculated total evapotranspiration by DCC method was consistent to that measured by the WB method at above“Satisfactory”level(0.50<NSEd0.65 and 0.60<RSRd0.70),and at“Very good”level(0.75<NSEd1.00 and 0<RSRd0.50)when compared to the SF method.However,the performance of the DCC method on monthly evapotranspiration was worse than on total evapotranspiration,and the consistency mostly was classified as“Unsatisfactory”(NSE≤0.50 and RSR>0.70)for the monthly evapotranspiration and as“Satisfactory”for the total evapotranspiration,respectively when compared with the WB and SF methods.Crop coefficients for the whole growth period were similar for all three methods,but the crop coefficient suggested by the DCC method was larger at the beginning and the late growth stages but smaller at the vigorous growth stage of cherry trees than those measured by using the WB and SF methods.It can be concluded that the DCC method is an effective tool to estimate total evapotranspiration in the whole growth period of cherry tree,but an improvement on accuracy of estimating monthly evapotranspiration of cherry trees is required.

Simple weighing lysimeters for measuring evapotranspiration and developing crop coefficients

Knowledge of cotton crop evapotranspiration(ET)is important in scheduling irrigations,optimizing crop production,and modeling ET and crop growth.The ability to measure,estimate,and predict ET and cotton crop water requirements can result in better satisfying the crop’s water needs and improving water use efficiency.Weighing lysimeters have been used for many years to measure and study water use,and to develop crop-coefficient functions necessary in estimating ET.Electronic weighing lysimeters,consisting of a steel outer tank and inner tank,electronic loadcell assemblies,and a PVC drain system,were designed,constructed,and installed.Each lysimeter cost approximately US$1700(in 2001)in materials,required two people and 40 hours of labor to construct,and were installed by two people using minimal excavation and hand tools.Daily ET data for cotton were collected from 2003 to 2006 to quantify cotton water-use and to develop crop coefficient functions.Seasonal water use ranged generally from 2 to 8 mm/d.Seasonal water-use patterns varied considerably among growing seasons due to variable environmental and crop-growth conditions,making determination of an“average”crop-coefficient function difficult.

Impact of Climate Change on Maize Potential Productivity and the Potential Productivity Gap in Southwest China

The impact of climate change on maize potential productivity and the potential productivity gap in Southwest China（SWC） are investigated in this paper.We analyze the impact of climate change on the photosynthetic,light-temperature,and climatic potential productivity of maize and their gaps in SWC,by using a crop growth dynamics statistical method.During the maize growing season from 1961 to 2010,minimum temperature increased by 0.20℃ per decade（p 〈 0.01） across SWC.The largest increases in average and minimum temperatures were observed mostly in areas of Yunnan Province.Growing season average sunshine hours decreased by 0.2 h day^（-1） per decade（p 〈 0.01） and total precipitation showed an insignificant decreasing trend across SWC.Photosynthetic potential productivity decreased by 298 kg ha^（-1）per decade（p 〈 0.05）.Both light-temperature and climatic potential productivity decreased（p 〈 0.05） in the northeast of SWC,whereas they increased（p 〈 0.05） in the southwest of SWC.The gap between lighttemperature and climatic potential productivity varied from 12 to 2729 kg ha^（-1）,with the high value areas centered in northern and southwestern SWC.Climatic productivity of these areas reached only 10%-24%of the light-temperature potential productivity,suggesting that there is great potential to increase the maize potential yield by improving water management in these areas.In particular,the gap has become larger in the most recent 10 years.Sensitivity analysis shows that the climatic potential productivity of maize is most sensitive to changes in temperature in SWC.The findings of this study are helpful for quantification of irrigation water requirements so as to achieve maximum yield potentials in SWC.

Ecohydrologic modeling of crop evapotranspiration in wheat(Triticum-aestivum)at sub-temperate and sub-humid region of India

Efficient water management of crop requires accurate irrigation scheduling which,in turn,requires the accurate measurement of crop water requirement.Reference evapotranspiration plays an important role for the determination of water requirements for crops and irrigation scheduling.Various models/approaches varying from empirical to physically base distributed are available for the estimation of reference evapotranspiration.This study identified most suitable reference evapotranspiration model for sub-temperate,sub humid agro-climatic condition using climatic and lysimeter data.The Food and Agriculture Organization(FAO)recommended crop coefficient values are modified for the local agro-climatic conditions.The field experiment was conducted in sub-temperate and sub-humid agro-climate of Solan,Himachal Pradesh,India.Actual crop evapotranspiration for different crop growth stages of wheat(Triticum-aestivum)has been obtained from water balance studies using lysimeter set-up.Field observed and computed individual-stage wise crop evapotranspiration values are compared,to identify the most suitable reference evapotranspiration model for computing crop evapotranspiration.Penman Monteith model shows close agreement with observed value with coefficient of determination,standard error estimate and average relative discrepancy values of 0.96,13.69 and-5.8,respectively.Further,an effort has been made to compare the accuracy of various widely used methods under different climatic conditions.

Evapotranspiration estimation using SEBAL algorithm integrated with remote sensing and experimental methods

Evapotranspiration is one of the most important elements of the hydrological cycle.Estimation of evapotranspiration is imperative for effective forest,irrigation,rangeland and water resources management as well as to increase yields and for better crop management.This study aims to evaluate the effectiveness of the Surface Energy Balance Algorithm for Land(SEBAL)in estimating evapotranspiration and crop coefficient of corn in the Mediterranean region of Adana province,Turkey.The Landsat 8 satellite images from March to September 2018 were used to acquire the coefficients of the respective bands.Then,the net radiation flux on the earth’s surface and the earth’s heat flux is obtained using incoming-outgoing radiation fluxes from albedo,surface emissivity coefficients,land surface temperature,and plant indicators.Next,the sensible heat flux is calculated by determining the hot and cold pixels under consideration via the atmospheric stability conditions.Finally,evapotranspiration maps are plotted.The crop coefficient of corn is also estimated with the respected maps being plotted.To validate the outcomes from the SEBAL algorithm,experimental methods were employed to calculate the evapotranspiration values and evaluated using suitable performance metrics.The results showed that the SEBAL generated evapotranspiration values are in high agreement with the FAO Penman-Monteith method registering the highest correlation(R=0.91)and the lowest error(RMSE=1.14).In addition,the SEBAL method registered the highest correlation values of 0.89,0.87 and 0.68 with Turk,Makkink and Hargreaves experimental methods,respectively.Moreover,the crop coefficients estimated using SEBAL also manifested an acceptable correlation with all methods.The highest correlation value registered was with the FAO Penman-Monteith method(R=0.98).The outcomes show that since the performance of the SEBAL algorithm in estimating the actual evapotranspiration and crop coefficient using Landsat 8 satellite images is acceptable,the SEBAL algorithm could be a very convenient method.Moreover,it could easily be assimilated into farming management systems and precision agriculture for better decision-making and higher yield.

Comparison of evapotranspiration and energy partitioning related to main biotic and abiotic controllers in vineyards using different irrigation methods

Knowledge of evapotranspiration(ET)and energy partitioning is useful for optimizing water management,especially in areas where water is scarce.A study was undertaken in a furrow-irrigated vineyard(2015)and a drip-irrigated vineyard(2017)in an arid region of northwest China to compare vineyard ET and energy partitioning and their responses to soil water content(SWC)and leaf area index(LAI).ET and soil evaporation(E)and transpiration(T)were determined using eddy covariance,microlysimeters,and sap flow.Seasonal average E/ET,T/ET,crop coefficient(Kc),evaporation coefficient(Ke),and basal crop coefficient(Kcb)were 0.50,0.50,0.67,0.35,and 0.29,respectively,in the furrow-irrigated vineyard and 0.42,0.58,0.57,0.29,and 0.43 in the dripirrigated vineyard.The seasonal average partitioning of net radiation(Rn)into the latent heat flux(LE),sensible heat flux(H)and soil heat flux(G)(LE/Rn,H/Rn,and G/Rn),evaporative fraction(EF)and Bowen ratio(β)were 0.57,0.26,0.17,0.69 and 0.63,respectively,in the furrowirrigated vineyard and 0.46,0.36,0.17,0.57 and 0.97 in the drip-irrigated vineyard.The LE/Rn,H/Rn,EF,andβwere linearly correlated with LAI.The E,Kc,Ke,E/ET,LE/Rn,LEs/Rn(ratio of LE by soil E to Rn),H/Rn,EF andβwere closely correlated with topsoil SWC(10 cm depth).Responses of ET and energy partitioning to the LAI and SWC differed under the two irrigation methods.Drip irrigation reduced seasonal average E/ET and increased average T/ET.From the perspective of energy partitioning,seasonal average H/Rn increased whereas LE/Rn,especially LEs/Rn,decreased.Compared with furrow irrigation,drip irrigation decreased the proportion of unproductive water consumption thereby contributing to enhanced water use efficiency and accumulation of dry matter.