Construção, automação e avaliação de um lisímetro de pesagem hidráulica

Abstract

This paper describes the construction procedures, automation and evaluation of a hydraulic weighing lysimeter for obtaining measurements of evapotranspiration in the region Rondonópolis - MT, the positions in SAD 69 ( South American Datum ) system are latitude 16°2’’15’ south and 54°38’’08’ west longitude at an altitude of 284 m. The measurements obtained in lysimeters with those obtained by the following methods Jensen - Haise, Penman-Monteith and Tank Class A. The lysimeter with an area of 1 m2 and 0.7 m deep, was constructed with iron plate. The same was coated by a jacket filled with concrete layer and 0.10 m of soil, the first layer being filled with gravel, containing within it three PVC pipes sieved, to facilitate drainage of water in the inner container and central tube to monitor soil moisture. After filling the lysimeter calibration was done with the addition and removal of weights 1 kg. Were also installed in the same area an automatic weather station, a device data acquisition (datalloger) and class A pan Periods of meteorological records of this work comprise of 01/08/2013 to 31/10/2013. With the results we conclude the relationship between the difference of standard weights 1 kg and the reading recorded at the gauge as the sensor were linear with (R2 = 0.99) in both the calibration and with central point load cells or load vertices of the same showed high stability of the readings. The calibration coefficient (k) for the datalogger was 1.017 and the average positional error was 4.09%. Daily measurements obtained by lysimeter ETo that best correlated with the estimated values were the Penman-Monteith (R2= 0.56) and compared with the estimates of Jensen Haise the coefficient of determination was (R2= 0.36) and the Class A pan (R2= 0.48).