Irrigation performance assessments for corn crop with Landsat images in the São Paulo state, Brazil

Abstract

Actual evapotranspiration (ET) and crop coefficient (Kc) were modelled in a commercial farm with corn crop.
The plots were irrigated by central pivots for grain and silage, in the north-western side of São Paulo State, Brazil. For ET
acquirements, the SAFER (Simple Algorithm For Evapotranspiration Retrieving) algorithm was applied to Landsat satellite
images during growing seasons (GS) from March to August of 2010. Polynomial functions relating Kc and the accumulated
degree-days (DD_ac) allowed the estimation of evapotranspiration under potential conditions (ETp). Adding data on reference
evapotranspiration (ET0), precipitation (P), irrigation (I) and productivity (Y_p), irrigation performances were assessed. The
Relative Evapotranspiration (R_ET) ranged from 0.78 to 1.00 and the Water Deficit (WD) presented a maximum of 110 mm
GS^-1. The Relative Water Supply (R_WS) with values from 1.1 to 1.4 indicated high drainage rates. The physical values of water
productivity, based on ET (WP_ET) ranged from 1.4 to 2.8 kg m^-3 for grains and from 8.8 to 14.1 kg m^-3 for silage, with the
corresponding monetary ones for grains from 0.34 to 0.68 US$ m^-3, showing high return when comparing with other annual
crops.