Actual evapotranspiration and crop coefficient of sweet orange during the initial development phase in the Rio Largo region, Alagoas

Ricardo Barros Silva,Renan Cantalice De Souza,Marcos Alex Dos Santos,José Leonaldo De Souza,Wellington Manoel Dos Santos,Ricardo Araújo Ferreira Júnior

doi:10.1590/0103-8478cr20180707

Ricardo Barros Silva, Renan Cantalice De Souza + Show 4 more

Open Access

https://doi.org/10.1590/0103-8478cr20180707

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Journal: Ciência Rural	Publication Date: Jan 1, 2019
License type: CC BY 4.0

Affiliation: Universidade Federal de Alagoas

Abstract

ABSTRACT: Determining actual crop evapotranspiration (ETa) is paramount for irrigation management. The principal measurement methods and physical models generally require crop and weather data that are not readily available. We determined the crop coefficient (Kc) of sweet oranges during the initial development stage and evaluated the performance of the Poulovassilis semi-empirical model coupled with a simple soil water balance for estimating the ETa. The ETa was inferred from the variation in the soil water content over time, measured by time-domain reflectometry. In the Poulovassilis model, the ETa is obtained by multiplying the crop evapotranspiration (ETc) by an adjustment coefficient (ca), which accounts for a reduction in the evapotranspiration caused by soil water depletion. Soil water storage was obtained using the daily and 10-day soil water balances, computed by considering inputs and outputs of water from the system. The empirical parameter, ca, was determined using inverse modeling. The optimal ca value obtained through inverse modeling was 0.05 and 0.03 for the daily and 10-day soil water balances, respectively. The model performed better for the daily soil water balance than the 10-day balance, with performance comparable with the other ETa models. Average Kc during the sweet orange initial crop stage was 0.85.

Highlights

Oranges are one of the most widely consumed fruits worldwide, either “in natura” or through derivatives, generating employment and income in the producing regions
The ca parameter of the Poulovassilis model is related to the shape of the evapotranspiration reduction curve
Some experimental studies (e.g., CONSOLI et al, 2014; GASQUE et al, 2016) have indicated that orange crops have a tolerance to water stress. These studies preclude any inference on the shape of the evapotranspiration reduction curve and; one cannot infer whether the low ca values computed here are characteristic of sweet orange or caused by the effects of both the soil and climatic conditions

Summary

Introduction

Oranges are one of the most widely consumed fruits worldwide, either “in natura” or through derivatives, generating employment and income in the producing regions. According to the IBGE (2018), Brazil was the world’s largest orange producing country in 2017, with a harvest of 17.5 million tons that corresponded to 23.8% of the global production and a yield of 27.6 t ha-1. The climatic conditions of the coastal table land region of Alagoas (which is unlike the other Northeastern micro-regions) favor orange. Considering crop’s climatic requirements (temperatures between 13 and 35 °C, annual rainfall between 600-1200 mm) (REUTHER, 1973; BEN MECHLIA & CARROLL, 1989), the region provides an adequate thermal availability (annual temperatures between 19 and 31 °C) and an average annual rainfall of 1818 mm. The rainfall distribution in this region is seasonal, with a dry season occurring during part of the year, which renders crop irrigation necessary (SOUZA et al, 2005)

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