Desenvolvimento e análise de funcionamento de Lisímetros de pesagem para determinação da evapotranspiração em videira de vinho cv Syrah (Vitis vinífera L)

Abstract

The objectives of this research work were: the installation, calibration and performance analysis of three load cell based weighing lysimeters, to monitoring the water demand of wine grape, the measuring of crop evapotranspiration (ETc) and crop coefficient (Kc) on initial development stages of wine grape cv. Syrah (Vitis vinifera L.) in Petrolina, Pernambuco State, Brazil. Three weighing lysimeters were constructed, with surface area of 2.4 m2 (1.2 m wide, 2.0 m long, 1.0 m deep), after the vineyard establishment of grape cv. Syrah grafted on rootstock 1103 Paulsen, in a grid spacing of 3 x 1 m, and irrigated by drip, with two emitters per plant, 2.5 L.h-1 flow. The reference evapotranspiration was estimated by Penman-Monteith FAO and class A pan methods. The lysimeters presented very good performance, a high linearship between load cell signals and lysimeter weight changes, excellent determination coefficient (r2=0.99), and low hysteresis. The lysimeters presented enough sensitivity to measure weight variation related to a 0.11 mm depth, with accuracy of 0.4, 0.6, and 1 mm for lysimeters 1,2, and 3, respectively. For a 33 days experimental time, the total ETc was 121 mm, with average values of 3.64 mm.day-1 and highest values of 6.11 mm.day-1. The average Kc values were 0.82 and 0.83 by Penman- Monteith FAO method,; and 0.99 and 1.00 by class A pan method, using lysimeters 1, 2, and 3, respectively. The Kc values obtained using the ETo estimative by class A pan method were 20% higher than those values obtained by ETo estimative Penmam-Monteith FAO method. It was concluded that the values determined by lysimeter ETc corroborates with the values found in other studies by different methods in the region. The lysimeters presented excellent performance to measure the weight changes on daily basis to estimate wine grape evapotranspiration and can be used as a basis for irrigation in the valley of São Francisco.