Mapping Maize Evapotranspiration at Field Scale Using SEBAL: A Comparison with the FAO Method and Soil-Plant Model Simulations

Carla Grosso,Marco Martello,Diego Pons,Gabriele Manoli,Yann Chemin,Pietro Teatini,Ilaria Piccoli,Francesco Morari

doi:10.3390/rs10091452

Abstract

The surface energy balance algorithm for land (SEBAL) has been successfully applied to estimate evapotranspiration (ET) and yield at different spatial scales. However, ET and yield patterns have never been investigated under highly heterogeneous conditions. We applied SEBAL in a salt-affected and water-stressed maize field located at the margin of the Venice Lagoon, Italy, using Landsat images. SEBAL results were compared with estimates of evapotranspiration by the Food and Agriculture Organization (FAO) method (ETc) and three-dimensional soil-plant simulations. The biomass production routine in SEBAL was then tested using spatially distributed crop yield measurements and the outcomes of a soil-plant numerical model. The results show good agreement between SEBAL evapotranspiration and ETc. Instantaneous ET simulated by SEBAL is also consistent with the soil-plant model results (R2 = 0.7047 for 2011 and R2 = 0.6689 for 2012). Conversely, yield predictions (6.4 t/ha in 2011 and 3.47 t/ha in 2012) are in good agreement with observations (8.64 t/ha and 3.86 t/ha, respectively) only in 2012 and the comparison with soil-plant simulations (8.69 t/ha and 5.49 t/ha) is poor. In general, SEBAL underestimates land productivity in contrast to the soil-plant model that overestimates yield in dry years. SEBAL provides accurate predictions under stress conditions due to the fact that it does not require knowledge of the soil/root characteristics.

Highlights

The growing world population needs more food, possibly with less water available for agriculture [1], making the wise management of water resources one of the great challenges of our times
Results confirm that surface energy balance algorithm for land (SEBAL) is a viable tool for calculating ET at field scale even under highly heterogeneous conditions
The comparison between daily ET estimated by the Food and Agriculture Organization (FAO) method and SEBAL shows good agreement in 2011 and 2012

Summary

Introduction

The growing world population needs more food, possibly with less water available for agriculture [1], making the wise management of water resources one of the great challenges of our times. This problematic situation can improve only if water is managed more effectively leading to increased crop yield per unit of water consumed (i.e., improving water use efficiency). Evapotranspiration (ET) is the largest sink of irrigation water and, thanks to well-established crop-specific relations between ET and yield [6,7], it provides a measure of both water demand and land productivity. Crop yield is a key element for rural development and national food security. For these reasons, forecasting crop yield a few months before harvest can be of paramount importance for timely initiation of the food trade, securing national demand, and organizing food transport within countries [6,7,12]

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Conclusion