Proceedings of International conference on Agricultural and Biological Sciences (ABS 2015) held in Beijing, China on July 25-27, 2015With larger planting areas being used in greenhouses, evaluating crop evapotranspiration in a greenhouse has garnered greater attention. Currently, calculating the reference crop evapotranspiration for a greenhouse crop through using the Penman-Monteith formula recommended by FAO is difficult because the wind speed in a greenhouse is approximate zero. In order to calculate reference crop evapotranspiration in a greenhouse by the Penman-Monteith modified formula, a simplified model for calculating reference crop evapotranspiration in a greenhouse was proposed based on the energy balance equation, which was the correlative function between reference crop evapotranspiration and radiation and temperature. The model's parameters were obtained through meteorological data taken from the inside of a greenhouse in 2011. Then, the model was validated by using meteorological data within the greenhouse in 2012, and the fitted value of the model agreed with the calculated value of the formulas with a determination coefficient (R2) of 0.9554. This model is an easy means of calculating the reference crop evapotranspiration in a greenhouse because less meteorological factors are needed. Furthermore, the model provides a theoretical basis for crop irrigation in greenhouses

Adaobi, U.P.

Chen, Z.F.

Duan, A.W.

Liu, H.

Liu, X.F.

Liu, Z.G.

Shen, X.J.

Sun, J.S.

Uzokwe, Veronica N.E.

Zhang, J.Y.

The Journal of Animal and Plant Sciences

CGSpace

Liu et al., J. Anim. Plant Sci. 25 (3 Suppl. 1) 2015 Special IssueProceedings of International conference on Agricultural and Biological Sciences (ABS 2015) held in Beijing, China on July 25-27, 2015141SIMULATION OF REFERENCE CROP EVAPOTRANSIRATION IN A PLASTIC SOLARGREEN HOUSE USING A SIMPLIFIED ENERGY BALANCE APPROACHX. F. Liu 1*, Z. G. Liu1*, A. W. Duan1*, J. S. Sun1#, H. Liu1, Z. F. Chen1, J. Y. Zhang1,  X. J. Shen, U. P. Adaobi1 and V.N. E. Uzokwe2Jiyang Zhang1, Xiaojun Shen, Uzokwe Pauline Adaobi1, Veronica NE Uzokwe21.Farmland Irrigation Research Institute, Chinese Academy of Agricultural Sciences/Key Lab of Crop WaterRequirement and Regulation of Ministry of Agriculture 453002, Xinxiang, China.2. International Institute of Tropic Agricultural, Dares Salaam-P.O. Box 34441, Tanzania.*These authors equally contributed to this paper. Both are considered as first author.#Corresponding Email: jshsun623@aliyun.comABSTRACTWith larger planting areas being used in greenhouses, evaluating crop evapotranspiration in a greenhouse has garneredgreater attention. Currently, calculating the reference crop evapotranspiration for a greenhouse crop through using thePenman-Monteith formula recommended by FAO is difficult because the wind speed in a greenhouse is approximatezero. In order to calculate reference crop evapotranspiration in a greenhouse by the Penman-Monteith modified formula,a simplified model for calculating reference crop evapotranspiration in a greenhouse was proposed based on the energybalance equation, which was the correlative function between reference crop evapotranspiration and radiation andtemperature. The model’s parameters were obtained through meteorological data taken from the inside of a greenhousein 2011. Then, the model was validated by using meteorological data within the greenhouse in 2012, and the fitted valueof the model agreed with the calculated value of the formulas with a determination coefficient (R2) of 0.9554. Thismodel is an easy means of calculating the reference crop evapotranspiration in a greenhouse because less meteorologicalfactors are needed. Furthermore, the model provides a theoretical basis for crop irrigation in greenhouses.Key words: Greenhouse, water requirement, reference crop evapotranspiration, simulation.INTRODUCTIONAs a kind of inverse season cultivation,vegetables that are planted in greenhouses are capable ofmaking full use of light, temperature, and othermeteorological elements for plant growth; therefore,greenhouses not only benefits farmers, but they also solvethe shortage of slack season vegetables. Furthermore,with the promotion of greenhouse crop cultivated area,the crop water requirement in a greenhouse has becomean important focus area for research. Greenhouses have aspecial environment that supports the growth of crops,unlike in fields where the water requirement variesgreatly.Extensive research into this area of study hasbeen conducted both at home and abroad. For example,Wu et al. (2005) summarized the study progress of soilwater and heat transport in greenhouses. Katsoulas et al.(2001) investigated the effect of greenhouse moisture oncanopy conductance of crop evapotranspiration. Inaddition, Li et al. (2001) reported the effects ofelectrolysis and transpiration on the yield of greenhousetomato under saline irrigation. Cecilia Stanghellini et al.(2011), Medrano et al. (2005), and Rouphael et al. (2005)analyzed the radiation effects on transpiration ofgreenhouse crops. Moreover, Boulard et al. (2004) andKichah et al. (2012) simulated crop evapotranspiration ina greenhouse based on the mechanism model of leafstomatal conductance and the computational fluiddynamics model, respectively. The aforementionedresearch work primarily estimated the evapotranspirationof greenhouse crops from its physiological mechanism.However, there is a need to measure the physiologicalparameters of greenhouse crops, but this method forestimating the evapotranspiration of greenhouse crop isnot easily or widely used.Crop water requirements are generallycalculated via the water balance method (test methods)and the reference crop method (theory of empiricalformula). In using the reference crop method to calculatethe crop water requirements, the first step is to calculatethe reference crop evapotranspiration and cropcoefficients. The reference crop evapotranspiration iscalculated using a modified Penman-Monteith formulathat is recommended by FAO in 1998 (Allen et al., 1998)and is mainly suitable for weather information in the field.With the development of protected agriculture as well asan increase in greenhouse planting area, studiesconducted on the water consumption, yield, and qualityof greenhouse crops are becoming major issues forinvestigation. The Penman-Monteith formula forcalculating the reference crop evapotranspiration in agreenhouse as recommended by FAO is asThe Journal of Animal & Plant Sciences, 25 (3 Suppl. 1) 2015 Special Iss e Page: 41-145ISSN: 1018-7081Liu et al., J. Anim. Plant Sci. 25 (3 Suppl. 1) 2015 Special IssueProceedings of International conference on Agricultural and Biological Sciences (ABS 2015) held in Beijing, China on July 25-27, 2015142follows:)34.01()(273900)(408.0220ueeuTGRETasn(1)Where:ETo –reference evapotranspiration, mm d-1; Rn -net radiation at the crop surface, MJ m-2 d-1; G — soilheat flux density, MJ m-2 d-1; T — mean daily airtemperature at 2 m height, °C; u2 —wind speed at 2 mheight, m.s-1; es —saturation vapor pressure, kPa; ea—actual vapor pressure, kPa; es-ea —saturation vaporpressure deficit, kPa; △ —slope of vapor pressure curve,kPa°C-1; r—psychrometric constant, kPa °C-1.However, because greenhouses have a hightemperature, a highly wet environment, and little windeffects, using the latest Penman-Monteith formularecommended by FAO to calculate the reference crop isdifficult. In calculating air dynamics impedance, Wang etal. (2006) and Chen et al. (2007 a, b) proposed that theair boundary layer within a daylight greenhouse belongsto a non-neutral stable stratification. They adopted theformula of calculating air dynamics impedance (ra) fromThom and Oliver (1977) to replace the impedanceformula amended by Allen et al. (1994) in the Penman-Monteith formula, which was adapted to consider the airboundary layer as belonging to a neutral stablestratification. Furthermore, the ET0 correction formula,which is suitable for greenhouse crops, was proposed andthen subsequently validated using both the panevaporation method and the water balance method.However, this corrected formula requires moremeteorological factors, and therefore, calculating theformula can be cumbersome. Thus, the formula cannot beused in a solar greenhouse with incompletemeteorological data.  Based on the above reasons, it isimportant to seek a simple approach of calculating thereference crop evapotranspiration in a greenhouse.Accordingly, an amended formula was proposed byWang Jian and is as follows:64.12731713GR408.0 n0  TeeETda ）（）（（2）The meaning of the symbols and units informula (2) are the same as above. The formula isexplained as follows:The corrected Penman-Monteith formulaprimarily consists of two parts. The first part is theradiation item, and the second is the aerodynamics item.In a greenhouse, the wind speed is close to 0, and bysubstituting U2=0 into formula (1), the aerodynamics itemof the reference crop evapotranspiration is 0. Therefore,this does not clearly match the physical meaning offormula (1), and as such, formula (1) cannot be used for adirect calculation of the reference crop evapotranspirationin a greenhouse. Wang et al.(2006) and Chen et al. (2007a, b) cited the formula for calculating the aerodynamicresistance proposed by Thom and Oliver and avoided thesituation at which the wind speed is close to 0 and theaerodynamic resistance is infinity. The corrected formulafor calculating the reference crop evapotranspiration in agreenhouse is more reasonable through experimentalverification. The model described above also requiresweather information and crop physiological indices,which are difficult to apply.  Based on the energy balance,the equation for estimating the reference cropevapotranspiration in a greenhouse with lessmeteorological data were derived.MATERIALS AND METHODSProcess of deriving model: The heat balance equationfor evapotranspiration is as follows:0 HLEGFrQQ (3)Where:Q — the total solar radiation, k.cm-2d-1; r —reflectivity (dimensionless); F —effectivelongwaveradiation, k.cm-2d-1; G — the soil heat storageor soil heatloss, k.cm-2d-1; L — the latent heat of evaporation, whichis 590k.g-1; E — evapotranspiration rate, mm.d-1; H —the heat exchange of near-surface vertical turbulent,k.cm-2d-1.By dividing both sides of the above equation byQ, it becomes:QHQGQFrQLE ///1/  （4）Jin and Yang (1981) synthesized the followingformula form through plotting E/Q～T:59/)08.0019.0( QTE  (5)We assume that there is a linear relationshipbetween the reference crop evapotranspiration (ET0) inthe greenhouse and E:ckEET 0 (6)Inserting formula (5) into formula (6), we obtain:  cQTkET  59/)08.0019.0(0 (7)As long as the coefficientsof k and c areobtained, ET0 has a function ofglobal solarradiation,Q,and mean temperature, T.Calibration of the model’s parameters: The waterrequirement of tomatoes in a solar greenhouse wasstudied at the crop water requirement observation site atthe Farmland Irrigation Research Institute of CAAS(North latitude 35.19°, longitude 113.53°, altitude 72.7m),from April to September 2011. The greenhouse was 40mlong and 8.5m wide with a 273m2 planting area.Moreover, it had sandy loam soil that was covered with aLiu et al., J. Anim. Plant Sci. 25 (3 Suppl. 1) 2015 Special IssueProceedings of International conference on Agricultural and Biological Sciences (ABS 2015) held in Beijing, China on July 25-27, 2015143drip-free polyethylene film, while the outer cover was athermal keeping quilt. Each day, it was opened at 8:00 amand closed at 18:30 pm. Additionally, the greenhouse hadno heating devices. It consisted of a 3.6m-high roof ridge,a 2.88m-high back wall, and a 0.42m-thick wall, withventilation holes (24cm × 24cm) that were 1.2m abovethe ground with a horizontal spacing of 3m. Its wallstructure consisted of 12cm of red brick, a 6cm thermalinsulation layer, and 24cmof red brick in thickness.Moreover, the wall foundation was a brick-concretestructure that was 76cm below ground, and the roofingskeleton was pre-galvanized steel pipes with Φ 1.0 inch-formed arch beams with 1.0m spacing. The front end ofthe arch beam had foam heat insulation panels that were30cm deep and 6cm thick, and below the panels, therewas a 10cm lime-soil cushion layer. Weather data wasobtained by an automatic weather station located withinthe greenhouse.By adopting the equation of calculating thereference crop evapotranspiration in a greenhouse thatwas proposed by Wang et al.(2006), combining theglobal solar radiation Q and mean temperature T in thegreenhouse, the coefficients of k and c were estimatedaccording to formula (7):K=1.2        c= -0.8Calculating the reference cropevapotranspiration in a greenhouse was then simplified tothe following:8.0)08.0019.0(02.00  TQET (8)RESULTS AND DISCUSSIONThe simplified formula (8) above and formula(2) that was presented by Wang et al.(2006) werevalidated as follows:The meteorological data collected whilegrowing tomatoes in a greenhouse from March 14 to July6, 2012, were used to validate the above formula.  Figure1 shows a scatter chart of the simulated values and actualcalculated values of the reference crop evapotranspirationfor a greenhouse crop. The simulated values represent thecalculated values of formula (8), and actual values werethe calculated values of formula (2). As can be seen fromFigure 1, there is a linear correlation between thesimulated values and the actual calculated values( XY 1.0702 ), with a correlation coefficient ofR2=0.9661 (n=155). Through statistical analysis, it wasdetermined that t=9.94, t0.05 (114), =1.99, and t0.01 (114) =2.64.Thus, the correlation was very significant both at thelevel of  = 0.05 and  = 0.01.  Table 1 reveals that themodel had a mean deviation (MD) of 0.18, a meanprediction error (MPE) of 0.20, a mean prediction squaredeviation (MSPE) of 0.07, a root-mean-square deviation(RMSE) of 0.27, and a skewness of 7.02.Figure 1. ET0 mapping between actual calculatedvalues and simulated valuesFigure 2. Change in ET0 trend over timeFigure 2 presents the changes in the ET0 curvesof the simulated value and actual calculated value withtime. From Figure 2, the ET0 of both the simulated andactual calculated values increased over time, as did boththe average temperature and sunlight intensity. BeforeJune, there was little difference in the ET0 between thesimulated values and actual calculated values, but afterJune, there was a greater deviation, which was consistentwith the results of Chen et al. (2007 a, b).Table 1.The error statistics of the modelError name MD MPE MSPE RMSENumerical value 0.18 0.20 0.07 0.27In March, April, and May, the heat generated bythe total solar radiation was small, and the temperaturechanges in the greenhouse were not obvious. However,unique meteorological conditions appeared in theLiu et al., J. Anim. Plant Sci. 25 (3 Suppl. 1) 2015 Special IssueProceedings of International conference on Agricultural and Biological Sciences (ABS 2015) held in Beijing, China on July 25-27, 2015144greenhouse in June, July, and August as there was bothhigh humidity and high temperatures present.Additionally, the total radiation items increased greatly inthe greenhouse due to the radiation reflected from theground and plastic cover, which then raised thetemperature in the greenhouse, and the greenhouse effectwas obvious. This led to greater simulated values. Inaddition, the high temperature and high humidity causedthe gradient of aerodynamic items to be reduced, whichalso resulted in great deviation in the simulated values.Furthermore, the simulation results of thereference crop evapotranspiration in a greenhouse thatwere obtained by different researchers(Möller et al.,2004; Tanny et al., 2006; Dicken et al., 2013; Pirkner etal., 2013) were different, but these differences werecaused by differences in methods, climate, and plantingcrops.Through simulating the reference cropevapotranspiration of a greenhouse crop based on energybalance, the simplified equation was proposed with fewerdata and high simulation accuracy, which results in asimple, easy, and accurate simulation of the referencecrop evapotranspiration of greenhouse crops.At present, there is not a common internationalstandard for simulating the reference cropevapotranspiration in greenhouse water requirements, andit was validated using different standards. Therefore, infuture research, a generic model will be established toimprove the simulation precision like the Penman-Moteith equation proposed by FAO in 1998. Afterestablishing a generic model, the crop coefficients in agreenhouse can be further calculated, which will play animportant role in developing the irrigation scheduling ofgreenhouse crops.Acknowledgments: This project was co-funded byProject supported by the National High TechnologyResearch and Development Program of China (GrantNo.2011AA100502 and 2011AA100509), the SpecialPublic Interest Fund for Agro-scientific Research (GrantNo.201203077), Innovation Project of CAAS and theJoint Funds of the National Natural Science Foundationof China (Grant No. U1404528 ).REFERENCESAllen, R.G., L.S. Pereira, D. Raes, and M. Smith (1998).Crop evapotranspiration guidelines forcomputing crop water requirements. FAOIrrigation and Drainage Paper 56, FAO-Foodand Agriculture Organization of the UnitedNations, Rome.Allen, R.G., M. Smith, and L.S. Pereira (1994).An updatefor the calculation of referenceevapotranspiration. ICID Bulletin. 43(2): 35−92.Boulard, T., H. Fatnassi, and J. Lagier (2004). SimpleIndirect Estimation of Ventilation and CropTranspiration Rates in a Greenhouse. Biosyst.Eng. 88(4):467-478.Chen, X.M., H.J. Cai, H.X. Li, J. Wang and W.J. Du(2007). Calculation of crop evapotranspiration ingreenhouse. Chinese J. Applied Ecology.18(2):317-321. (in Chinese)Chen, X.M., H.J. Cai, H.X. Li, and J. Wang (2007).Calculation and verification of cropevapotranspiration in greenhouse. Advances inWater Science. 18(6):812-815. (in Chinese)Dicken, U., S. Cohen, and J. Tanny (2013). Effect ofplant development on turbulent fluxes of ascreenhouse banana plantation. Irrig. Sci. 31 (4):701–713.Jin, D.L. and S.C. Yang (1981). Method of calculatingsoil evaporation using general weatherinformation. Yangtze River. (4): 30-35. (inChinese).Katsoulas, N., A. Baille,and C. Kittas (2001). Effect ofmisting on transpiration and conductances of agreenhouse rose canopy. Agric. For. Meteorol.106(3): 233-247.Kichah, A., P. Bournet, C. Migeon, and T. Boulard(2012). Measurement and CFD simulation ofmicroclimate characteristics and transpiration ofan impatiens pot plant crop in a greenhouse.Biosyst. Eng.112 (1):22-34.Li, Y.L., C. Stanghellinia, and H. Challa (2001).Effect ofelectrical conductivity and transpiration onproduction of greenhouse tomato(lycopersiconesculentuml.). Sci. Hortic.88(1):11-29.Medrano, E., P. Lorenzo, and M. Sánchez(2005).Evaluation and modelling of greenhousecucumber-crop transpiration under high and lowradiation conditions. Sci. Hortic. 105(2):163-175.Möller, M., T. Tanny, Y.Li, and S.Cohen (2004).Measuring and predicting evapo-transpiration inan insect-proof screenhouse. Agric. For.Meteorol. 127 (1–2):35–51.Pirkner, M., U. Dicken, and J. Tanny (2013). Penman–Monteith approaches for estimatingcropevapotranspiration in screenhouses—a casestudy with table-grape. Int. J. Biometeorol.58(5):725-737.Rouphael, Y.and G. Colla (2005). Radiation and wateruse efficiencies of greenhouse zucchini squashin relation to different climate parameters. Eur.J. Agron. 23(2): 183-194.Stanghellini, C., J. F. Dai, and F. Kempkes (2011). Effectof near-infrared-radiation reflective screenmaterials on ventilation requirement, croptranspiration and water use efficiency of agreenhouse rose crop. Biosyst. Eng.110 (3):Liu et al., J. Anim. Plant Sci. 25 (3 Suppl. 1) 2015 Special IssueProceedings of International conference on Agricultural and Biological Sciences (ABS 2015) held in Beijing, China on July 25-27, 2015145261-271.Tanny, J., L. Haijun, and S. Cohen (2006). Airflowcharacteristics, energy balance andeddycovariance measurements in a bananascreenhouse. Agric. For. Meteorol. 139 (1-2):105–118.Thom, A.S. and R. Oliver H. (1997). On Penman’sequation for estimating regional evaporation.Quart. J. Roy. Meteor. Soc. 103(436):345 - 357.Wang, J., H.J. Cai, H.X. Li, and X.M Chen (2006). Studyand evaluation of the calculation methods ofreference crop evapotranspiration in solar-heatedgreenhouse. J. Irrigation and Drainage.25(6):11-14.(in Chinese)Wu, W. Y., P. L. Yang, and H. L. Liu (2002). Retrospectand prospect on researches of water and heattransfer in Soil-Plant-Environment Continuum(SPEC) in greenhouse. J. Irrigation andDrainage. 21(1): 76-78. (in Chinese).

Simulation of reference crop evapotransiration in a plastic solar green house using a simplified energy balance approach

https://cgspace.cgiar.org/bitstream/10568/72897/1/U15ArtLiuSimulationInthomDev.pdf

Simulation of reference crop evapotransiration in a plastic solar green house using a simplified energy balance approach

Abstract

Similar works

Full text

Available Versions

CGSpace