Fraction of canopy intercepted radiation relates differently with crop coefficient depending on the season and the fruit tree species

doi:10.1016/j.agrformet.2013.08.008

Agricultural and Forest Meteorology

Volume 184, 15 January 2014, Pages 1-11

https://doi.org/10.1016/j.agrformet.2013.08.008 Get rights and content

Highlights

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The fraction of crop intercepted radiation is used to model irrigation requirements.
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We question such method by using lysimeter data and CropSyst model.
•
The influence of intercepted radiation was not constant throughout the seasons.
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The influence of fraction of intercepted radiation depended on each studied case.
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Such a seasonal influence can be predicted by optimizing two CropSyst parameters.

Abstract

It is commonly assumed that the fraction of canopy intercepted radiation (f_IR) should be well correlated with irrigation crop coefficients (Kc) throughout the season. However, in fruit trees there is some evidence that such a correlation is different between pre-harvest and postharvest periods. Over two different years, basal Kc (K_cb) data from three different weighing lysimeters (one in California growing peach trees, and the other two in Catalonia growing apple and pear trees) were analyzed using two parameters of the CropSyst growth model: full canopy Kc (Kc_fc) and maximum plant hydraulic conductance (C_max). In CropSyst, K_cb is approximated as f_IR times Kc_fc. The latter is usually seasonally fixed, but for this study it was made variable so that it could be adjusted every fortnight throughout the season. Variable Kc_fc implies the possibility that the K_cb relationship with f_IR is not constant. The objective of this study was to evaluate possible seasonal patterns in the Kc_fc. The results indicated that Kc_fc was variable in all species and it followed a distinctive pattern in three different time periods: (i) initial rise (spring), (ii) plateau or slight decline (mid-summer), and (iii) decline (autumn). However, the magnitude of Kc_fc fluctuation was different among the three species. It fluctuated the most in the slowest growing species (pear), and the least in the fastest growing species (peach). Apple had an intermediate response. In conclusion, Kc is not a fixed function of f_IR. Assumption of a fixed function will introduce errors in plant water use estimation, which could be especially large in pears and apples. This will be by 50% in pears during postharvest.

Introduction

Modern fruit production is facing the challenge of limited water resources. In order to optimize irrigation it is necessary to improve the accuracy of irrigation scheduling programmes. Water requirements can be calculated using the following equation: ETc = (Kcb + Ke) × ETo (Allen et al., 1998), where ETc is crop evapotranspiration, ETo is the reference evapotranspiration, Kcb is basal crop-specific coefficient that primarily represents plant transpiration, and Ke accounts for soil evaporation. Accurate determination of Kc (Kcb + Ke) is a prerequisite for sound irrigation scheduling. It is widely acknowledged that the fraction of crop intercepted radiation (f_IR) is a major determinant of Kc (Suay et al., 2003). It represents the energy that can be absorbed by the canopy and therefore be used for transpiration, and it has been assumed that the relationship between absorbed energy and transpiration does not change throughout the season (Pereira et al., 2007). This is supported by the literature published on peach growing in lysimeters in California reporting that noon intercepted radiation produced a significant linear relationship with Kc (Ayars et al., 2003, Johnson et al., 2005). However, experiments done in apple and pear lysimeters in Catalonia indicated that Kc showed moderate declines after harvest without changes in canopy foliage (Girona et al., 2011). Auzmendi et al. (2011) explained such declines after apple harvest by a reduction in the ratio of transpiration to intercepted radiation. This seems to emphasize that there are also other factors to consider such as canopy conductance. Therefore, there seems to be some basis for challenging the assumption of constancy in the relation between f_IR and Kc. For instance it has been found that fruit sinks are related to leaf conductance which decreases when fruit are thinned or harvested in peach (Marsal and Girona, 1997). In terms of tree transpiration, this has also been shown in apple (Reyes et al., 2006).

Such a principle of constancy has been successfully used in modelling to calculate evapotranspiration for annual crops in CropSyst (CS) (Stöckle et al., 2003). In CS the f_IR is used as a multiplier coefficient of maximum evapotranspiration to separate crop transpiration from soil evaporation. This maximum ET is calculated as ETo times Kc_fc, where Kc_fc is a parameter of the model which corresponds to Kc for a canopy that is fully covering the ground. In simulations for annual crops, Kc_fc has one single value for the season. However, for deciduous fruit trees, our hypothesis is that Kc_fc may be variable depending on the species and time of the year. Our objective was to find out if Kc_fc fluctuated according to a clear seasonal pattern and if this occurred similarly for three different deciduous tree species. Eventually, Kc_fc optimization in CS would serve to adequately simulate crop ET throughout the season for the species studied.

Section snippets

Model description

CropSyst is a comprehensive cropping systems model that covers a broad range of production and environmental factors (Stöckle et al., 2003). A manual of CropSyst with full description of input parameters and file management is available at http://www.bsyse.wsu.edu/CS_Suite/. In recent modifications, CS has been made applicable to deciduous trees. Although species specific applications need to be calibrated, it has been successful at simulating plant water stress in pear trees during short

Results

Agreement between CS outputs and measured values of ET, K_cb, and Ψ_stem throughout the full canopy cover period could only be optimized when Kc_fc and C_max were variable and not fixed. These variations depended on the time of the year and the species considered.

Discussion

CropSyst offered the opportunity of considering the environmental influences on K_cb as dependent on two components, f_IR and Kc_fc (Eq. (4)). Although the three species analyzed in this study are mesic deciduous fruit trees, they differed in vegetative growth rate. Pear was the least vigorous because it was grafted onto a rootstock (quince MA) that confers remarkable growth control to ‘Conference’ due to limited carbon storage in the roots (Lopez et al., 2013) and a degree of incompatibility in

Conclusions

Kc_fc was not constant throughout the season for any of the three species analyzed. They differed in their seasonal variation of Kc_fc. The variation was low in peach, and high for apple and pear. The lower variation in peach grown in California implied that irrigation scheduling was less prone to errors when based on a constant Kc_fc throughout the season. However, in apple and pear, scheduling errors would be more important due to Kc_fc fluctuations. The use of multiple Kc_fc values allowed CS to

Acknowledgements

The authors would like to thank the insights of Profs Theodore DeJong and Hossein Behboudian to this manuscript. This study was funded by INIA (RTA2009-00026-C02) and the Spanish Ministry of Education and Science (CONSOLIDER CSD2006-00067).

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Fraction of canopy intercepted radiation relates differently with crop coefficient depending on the season and the fruit tree species

Highlights

Abstract

Introduction

Section snippets

Model description

Results

Discussion

Conclusions

Acknowledgements

Agric. Water Manage.

Biosyst. Eng.

Agric. For. Meteorol.

Agric. Water Manage.

Sci. Hortic.

Eur. J. Agron.

Crop evapotranspiration: guidelines for computing crop water requirements

Irrigation and Drainage. Paper No. 56

Water use by drip-irrigated late-season peaches

Irrig. Sci.

The effect of three rootstocks on water use, canopy conductance and hydraulic parameters of apple trees and predicting canopy from hydraulic conductances

Plant Cell Environ.

Photosynthetic rate and diffusion conductance as a function of age in leaves of bean plants

Crop Sci.

Seasonal patterns of reproductive and vegetative sink activity in early and late maturing peach (Prunus persica) cultivars

Physiol. Plant.

Modeling peach fruit growth and carbohydrate requirements: reevaluation of the double-sigmoid growth pattern

J. Amer. Soc. Hort. Sci.

Crop water requirements

Irrigation and Drainage. Paper No. 24

Fluid flow in the outermost xylem increment of a ring-porous tree, Ulmus Americana

Am. J. Bot.

Localized graft incompatibility in pear/quince (Pyrus communis/Cydonia oblonga) combinations: multivariate analysis of histological data from 5-month-old grafts

Tree Physiol.

Leaf age and seasonal effects on light, water and nitrogen use efficiency in a California shrub

Oecologia

Yield response to water of fruit trees and vines: guidelines

A comparative study of apple and pear tree water consumption measured with two weighing lysimeters

Irrig. Sci.