Soil water stress co-efficient for estimating actual evapotranspiration of maize in northeastern Brazil.

Lyra, Gustavo Bastos; de Souza, José Leonaldo; da Silva, Eduardo Cabral; Lyra, Guilherme Bastos; Teodoro, Iedo; Ferreira‐Júnior, Ricardo Araújo; de Souza, Renan Cantalice

ABSTRACT Several of the methods used to estimate actual evapotranspiration ( ETa) consider the crop evapotranspiration ( ETc) to be affected by a soil water stress co-efficient (Ks) such that ETa = Ks ETc. The aim of this study was to assess the ETa estimation in maize in Alagoas State (09 ° 38 ′ S and 36 ° 40 ′ W; 260 m msl) in northeastern Brazil using the method of the single crop co-efficient from the FAO-56 paper, combined with three different approaches to determine Ks. The Ks was expressed as either a linear (Ks,lin) or a logarithmic (Ks,log) function of the soil water depletion. Additionally, the method proposed in the FAO-56 (Ks,FAO) was used when the impact was linear, but it was switched on after only one offset. Meteorological and soil water measurements were conducted in a maize crop from July to October 2005. The estimates of ETa were compared with the ETa determined from soil water balance. The ETa estimated with Ks,lin had the highest precision ( r2 = 0.67) and accuracy ( d = 0.89 and root mean square error ( RMSE) = 0.67 mm d−1). However, the ETa determined from Ks,log ( r2 = 0.41, d = 0.57 and RMSE = 1.69 mm d−1) or Ks,FAO ( r2 = 0.46, d = 0.62 and RMSE = 1.73 mm d−1) was not estimated successfully. When the parameters of Ks,FAO were fitted to the local edaphoclimatic conditions, the precision (0.67) and accuracy (0.89 and 0.82 mm d−1) were similar to the estimates with Ks,lin but with a better performance for ETa > 3.0 mm d−1.

EVAPOTRANSPIRATION; SOIL moisture; CORN research; GROUNDWATER; EVAPORATION (Meteorology)

Meteorological Applications, 2016, Vol 23, Issue 1, p26

1350-4827

Academic Journal

10.1002/met.1516