Wind speed and direction on water application uniformity of a mechanical lateral-move irrigation system

Abstract

In order to develop models for representation of Christiansen‘s Uniformity (CU) and Distribution Uniformity (DU) as a function of wind speed, 32 in-field tests evaluating a mechanical lateral-move irrigation system, used in rice production, were carried out in southern Rio Grande do Sul, Brazil. These tests were used to generate two third-order polynomial models for estimation of CU and DU, which were then validated based on a cross-validation approach. The generated models had their accuracy quantified by means of the following statistical measures: determination coefficient (R2), reliability and performance index (c), root mean square error (RMSE), and Nash-Sutcliffe coefficient (CNS). Wind direction had no significant influence on CU and DU. The CU values estimated from the cross-validation method were compared to those observed, resulting in R2 = 0.44, c = 0.53, RMSE = 1.82%, and CNS = 0.43. Likewise, DU values estimated from the cross-validation method were compared to the observed values, culminating in R2, c, RMSE, and CNS equal to 0.41%, 0.51%, 2.81% and 0.40%, respectively. The models developed in this study can be useful as a support tool for decision making when applying mechanical lateral-move irrigation systems, allowing estimation of CU and DU values with satisfactory precision for wind speeds less than 5.5 m s-1.