Development and Evaluation of an Irrigation Management Tool

Abstract

This study aimed to develop a tool for irrigation management and to evaluate its performance. To this end, 10 lysimeters, developed from plastic buckets, 20 L in volume, were installed. The inner volume of the buckets was divided into two parts. The lower half was filled with water. The upper half was filled with soil, grown with Bermuda grass. In the interior of the soil, a porous capsule was installed, connected to a plastic tube, which the lower border was immersed into the water of the lower part. As the crop extracted water from the soil, the soil sucked water from the lower part through the porous capsule. By lowering the water level in the bucket between two periods, the initial level was restored by addition of water through the feeder tube. The volume of water spent to restore the initial level divided by the bucket superficial area determines the evapotranspiration in that period. The tool was called Simplified Lysimeter -SIL. To evaluate the performance of the SIL, the following were considered: the correlation (r) and determination (r 2 ) coefficients, Willmott agreement (d), and Camargo & Sentelhas performance (c) and standard error estimate (SEE), taking PenmanMonteith-FAO as reference. According to results obtained, the SIL, developed with easily accessible and low cost materials and easy to construct, had a performance classified as very good and overestimated the evapotranspirarion obtained by PM at 0.30 mm d -1 , on average, showing good operating conditions and allowing to estimate evapotranspiration in agreement with Penman-Monteith estimates.