New approaches to evapotranspiration and transpiration measurements of stone fruits and table grapes

• Autores: Kosana Suvocarev
• Directores de la Tesis: Antonio Martínez Cob (dir. tes.)
• Lectura: En la Universidad de Zaragoza ( España ) en 2014
• Idioma: español
• Tribunal Calificador de la Tesis: Jordi Marsal i Vila (presid.), Asunción Usón Murillo (secret.), Diego Sebastiano Intrigliolo Molina (voc.)
• Materias:
  • Ciencias agrarias
• Enlaces
  • Tesis en acceso abierto en: Digital CSIC
• Resumen

  • INTRODUCTION The greatest part of agricultural water requirements is related to irrigation. It is a fundamental part of the Spanish system of agriculture and food production. There is about 3.4 Mha of irrigated land. It contributes with more than 50 % of the final agricultural production while it occupies only 13 % of the land surface that is used for cultivation. On average, irrigation increases about six times the crop production in comparison to the rainfed agriculture and it generates four times higher incomes. The knowledge of crop water requirements or crop evapotranspiration (ETc) and crop transpiration (Tc) is paramount for responsible and adequate irrigation scheduling and management. There is also the announcing need for setting values for the new growing practices, that lead to lower ETc or Tc rates without the appraisal of any kind of stress, such as cropping under netting. There are numerous methods for evapotranspiration, evaporation and transpiration measurements and determination. They differ according to the basis of methodology, type of evaporating surface, available input data, and time interval for which they can be used. The most precise methods for ETc measurement are direct measurements by weighting lysimeters and eddy covariance (EC). Where applicability of those two methods is limited, the surface renewal (SR) is proposed as a good alternative.

    The objectives of this research were, first, to evaluate the performance and applicability of the SR method following two approaches exempt from calibration over a sparse crop surfaces (late and early-maturing peach orchards) when compared to values obtained by the EC method: a) that proposed by Castellví et al (2006; 2008) and b) that proposed by Shapland et al. (2012a; 2012b); second, to measure the ETc and Kc of an early-maturing peach orchard by that SR approach found to be more adequate according to the energy balance closure and its applicability in sparse crops both under stable and unstable atmospheric conditions; third, to measure the crop transpiration (Tc) by the sap flow Tmax method and determination of the basal crop coefficients of two seedless cultivars of table grape grown under the semiarid Mediterranean climate, adjusted to special crop management conditions, i.e. the presence of netting (Kcbadj); forth, to development the early-maturing peach Kc and table grape Kcbadj curves as a function of thermal units and additional weather data.

    THEORY Understanding the soil¿plant¿atmosphere continuum lies in measurements and determination procedures of the surface energy exchange. The energy balance closure is used as a standard procedure to independently evaluate scalar flux estimates derived by micrometeorological methods (Wilson et al., 2002). The surface renewal (SR) has been experimented in the last three decades as a simplified alternative to procedures such as of eddy covariance (EC) in turbulent flux measurements (Paw U et al., 1995, 2005; Snyder et al., 1996; Spano et al., 1997). Methodologically, SR is based on canopy layer turbulence and the time-space scalar field associated with the dominance of turbulent coherent structures. The main challenge facing the SR method is in deriving the calibration factor (¿), thus making SR dependent on other direct surface exchange measurements such as EC. Because of the importance of accurately determining crop water needs, there has been a great effort to develop SR methods that will independently measure sensible (H) and latent (LE) heat fluxes (Castellvi et al., 2006, 2008; Shapland et al., 2012a; 2012b); LE is the energy equivalent for ET. Castellvi (2004) proposed combining SR analysis with similarity theory to auto-calibrate SR, which requires also average wind speed measurements. Castellvi et al. (2006, 2008) showed that this approach (SRCas) estimations improved energy balance closure in comparison to EC when applied over homogeneous crop surfaces. Recently, Shapland et al. (2012a, 2012b) proposed a SR method (SRShap) for independent flux estimation by distinguishing the larger turbulent coherent structures responsible for the flux interchange from the smaller non-flux-bearing isotropic turbulence. Their approach demonstrated that no calibration was needed under unstable atmospheric conditions over bare soil and homogeneous short canopies. Under the hypothesis that the smallest scale turbulent structures (Scale One) mix the larger scale coherent structures (Scale Two), which are responsible for direct energy and mass exchange, ¿ values are shown to be about 1.00.

    There have not been previous results reported on the application of the SRCas or SRShap approaches for calculating H and LE over sparse canopies, such as those in fruit orchards, where the turbulence can be enhanced by the presence of an uneven ground cover and the assumptions behind similarity theory may not be fulfilled.

    Recently, the use of insect-proof netting has widespread in orchard crops to reduce pesticide applications, radiative load during summer and hail and bird damage. The netting has a relatively low cost compared to total production costs in these orchard crops. Netting might have an important effect on microclimate and crop water requirements. There is little information about the effect of netting on crop water use in table grapes. Frequently, table grape vineyards are trained to an overhead trellis system which leads to an almost full ground cover shading. This, and the use of netting in drip-irrigated table grapes grown in semiarid regions, cause that transpiration represents most of the total ETc during mid-season stages due to minimum soil E because wetted soil surface areas are shaded (Allen et al. 1998), and to the low rainfall that generally occurs during that stage. Therefore, the quantification of Tc becomes crucial for appropriate irrigation scheduling of such drip-irrigated crops. To measure Tc the most commonly used method is sap flow. The so-called Tmax approach is useful for crops with the large xylem vessels such as table grapes (Green et al. 2003).To our knowledge, no previous works have been reported on the effect of the netting on table grape transpiration.

    Where measuring ETc and Tc by complex approaches and instrumentation is not possible, it can be estimated by using climatological methods. The approach commonly used to estimate ETc and Tc is that described by Allen et al. (1998) also known as the FAO-56 procedure. This approach suggests using the FAO Penman-Monteith equation for calculating ETo, to express the evaporative demand of the atmosphere and it must include meteorological data recorded at a standard reference weather station. The effects of characteristics that distinguish the cropped surface from the reference surface are reflected in the crop coefficient (Kc). ETc is then estimated as the product of ETo and Kc: ETc = Kc x ETo (Allen et al. 1998). And Tc is estimated as Tc = Kcb x ETo, where Kcb represents the basal crop coefficient that accounts only for Tc process, excluding the soil evaporation. Allen et al. (1998) and Allen and Pereira (2009) present tabulated values of both Kc (single approach) and Kcb (dual approach). The application of this FAO-56 procedure for ETc and Tc generally leads to using fixed Kc and Kcb curves along different years without taking into account the year-to-year variability. Use of thermal units (TU) to estimate Kc or Kcb has been proposed as a good alternative to take into account such variability. Expressions by Ritchie and NeSmith (1991) are useful, where air temperature is needed to compute TU and fraction of TU (FTU). Based on preliminary visual inspection of Kc and Kcb curves, the following variables were here tentatively used to model the measured Kc and Kcb: FTU, minimum relative humidity, wind speed, and accumulated precipitation for various periods.

    CONCLUSIONS The results confirmed the good performance of auto-calibration SRCas approach under different atmospheric stability conditions despite that some lack of similarity for temperature and water vapor exchange is possible under stable atmospheric conditions. The different statistics (D, slope, intercept and RMSE) show that SRCas performs better than EC because it showed similar or slightly better energy balance closures. SRShap showed similar tendency like SRCas but the performance was poorer. Expressing the RMSE values in terms of water depth (ET), the average uncertainty of the SRCas method compared to the EC method was very small, around 0.07 mm h-1.

    When SRCas was applied over data recorded by EC equipment for early-maturing peach crop ETcexp values ranged between 2.8 to 6.5 mm day-1 in 2010, with an average of 4.9 mm day-1, while they were 2.2 to 6.2 mm day-1 in 2011, with an average of 4.5 mm day-1. For 2010 and 2011, Kcexp values were about 0.4 to 0.6 in the crop development stage; they increased up to values of 0.8 around harvest and slightly decreased to about 0.75 after harvest; and finally there was some increase late in the season up to 0.85-0.9 due mainly to the soil and canopy intercepted rain water evaporation because of the late-season rain events.

    When sap flow Tmax method was applied to two seedless cultivars of table grape only slight differences in T and Kcbadj were observed in this study between the two cultivars and the two seasons. Average experimental Tc values for Crimson and Autumn Royal for 2009 were 4.4 and 4.3 mm day-1, respectively, while average transpiration values for Crimson, for 2008 and 2009, were 4.0 and 3.9 mm day-1, respectively. Average values of Kcbadj for Crimson and Autumn Royal were around 0.60 and for Crimson for 2008 and 2009 0.65, respectively. These results point out to that the presence of netting system has reduced the Tc rates. Further research would be required to obtain more accurate reduction coefficients due to netting.

    The model describing Kc values used statistically significant variables to explain variability in year-to year conditions. In the case of early-maturing peach FTU, RHn and Pri showed to be significant. The model explained up to 73 % of the Kcexp values. During validation, the results showed a good agreement between modeled and experimental values of ET: regression slope was no significantly different than 1.0, R2 = 0.87, RMSE = 0.45 mm day-1, and dr = 0.77. The model should be useful for estimating early-maturing peach ET under the same ground cover fraction, shallow soils and semiarid conditions of this study. Neverthless, it should be validated in other orchards to confirm its applicability as we were limited to validate it using only one season (2009), in the same study area and the crop was under mild to moderate water stress.

    For table grape vineyard under netting, only FTU is found to be significant for Kcb model. It was able to explain up to 69 % of the observed variability in Kcbadj. This equation should be limited to the late development and mid-season stages and similar conditions of this study.

    After further validation for other cultivars with different cumulative thermal requirements, the equations developed in this thesis could be considered helpful for farmers as a practical estimation procedure of Kc or Kcbadj. All variables needed for the models are easily accessible from networks of standard weather stations.

    REFERENCES Allen, R.G., Pereira, L.S., 2009. Estimating crop coefficients from fraction of ground cover and height. Irrig. Sci. 28, 17¿34.

    Allen, R.G., Pereira, L.S., Raes, D., Smith, M., 1998. Crop Evapotranspiration ¿ Guidelines for Computing Crop Water Requirements. FAO Irrigation and Drainage Paper 56. FAO, Rome, Italy.

    Castellví, F., 2004. Combining surface renewal analysis and similarity theory: a new approach for estimating sensible heat flux. Water Resour. Res. 40, W05201 doi: 10.1029/2003WR002677 Castellví, F., Mart¿nez-Cob, A., Pérez-Coveta, O., 2006. Estimating sensible and latent heat fluxes over rice using surface renewal. Agric. For. Meteorol. 139, 164¿169.

    Castellví, F., Snyder, R.L., Baldocchi, D.D., 2008. Surface energy-balance closure over rangeland grass using the eddy covariance method and surface renewal analysis. Agric. For. Meteorol. 148, 1147¿1160.

    Green, S., Clothier, B., Jardine, B. 2003. Theory and Practical Application of Heat Pulse to Measure Sap Flow. Agron J 95 (6): 1371-1379.

    Paw U, K.T., Qiu, J., Su, H.B., Watanabe, T., Brunet, Y., 1995. Surface renewal analysis: a new method to obtain scalar fluxes without velocity data. Agric. For. Meteorol. 74, 119¿137.

    Paw U, K.T., Snyder, R.L., Spano, D., Su, H.B., 2005. Surface renewal estimates of scalar exchanges. Micrometeorology in Agricultural Systems, Agron. Monogr., vol. 47, pp. 445¿484, ASA-CSSA-SSSA Publishers, Madison, Wisc.

    Ritchie J.T., NeSmith D.S. 1991. Temperature and crop development. In: Modeling Plant and Soil Systems. Hanks J., Ritchie J.T. (eds.). Series Agronomy Nº 31. 5-29. American Society of Agronomy, Crop Science Society of America, Soil Science Society of America, Madison, WI, USA.

    Shapland, T.M., McElrone, A.J., Snyder, R.L., Paw U, K.T., 2012a. Structure function analysis of two-scale scalar ramps. Part I: theory and modelling. Bound. Layer Meteorol. 145, 5¿25. http://dx.doi.org/10.1007/s10546-012-9742-5.

    Shapland, T.M., McElrone, A.J., Snyder, R.L., Paw U, K.T., 2012b. Structure function analysis of two-scale scalar ramps. Part II: ramp characteristics and surface renewal flux estimation. Bound. Layer Meteorol. 145, 27¿44. http://dx.doi.org/ 10.1007/s10546-012-9740-7.

    Snyder, R.L., Spano, D., Paw U, K.T., 1996. Surface renewal analysis for sensible and latent heat flux density. Bound. Layer Meteorol. 77, 249¿266.

    Spano, D., Snyder, R.L., Duce, P., Paw U, K.T., 1997. Surface renewal analysis for sensible heat flux density using structure functions. Agric. For. Meteorol. 86, 259¿271.

    Wilson, K., Goldstein, A., Falge, E., Aubinet, M., Baldocchi, D., Berbigier, P., Bernhofer, C., Ceulemans, R., Dolman, H., Field, C., Grelle, A., Ibrom, A., Law, B.E., Kowalski, A., Meyers, T., Moncrieff, J., Monson, R., Oechel, W., Tenhunen, J., Valentini, R., Verma, S., 2002. Energy balance closure at FLUXNET sites. 113,223¿243