Estimativa da transpiração em cafeeiros utilizando sensores de dissipação térmica

Abstract

The increase in productivity with the use of irrigation can be achieved by improved efficiency and accuracy of the use of the technique in the field. Some methods are capable to directly determine the amount of water consumed by a plant, among them, there is the "heat dissipation method" or Granier method. The aim of this study was: Track the sap flow in 24 adult plants of Coffea arabica; Evaluate according to the position of insertion of the sensor in the plant (North, South, East or West) and compared the results with the meteorological elements, such as radiation, temperature, relative humidity and too the evapotranspiration estimated by the Penman-Monteith equation. The coffee plantation with 3 years, located in Garanhuns-PE is drip irrigated. Were installed in 24 coffee sensors, thermal dissipation adapted from Granier (1985), where the set thermocouple and resistance were inserted the needle. The angle of insertion varied in each treatment, were installed tensiometers at different depths of soil and measured the leaf area, the diameter of the trunk and height of crop coffee. The design was used completely randomized to 4 treatments and 6 repetitions, Tukey test was done at 5% significance. With sensors built and installed in the plants were determined the density of sap flow from the variation of the difference in temperature between the probes and monitor the transpiration depending on the transition between day and night periods. The heights of the plants ranged between 1,91 and 2,5 m, leaf area of3,67 and 12,25 m2, maximum and minimum respectively. There was no significant difference between the angles of insertion to the sap flow. The experiment was divided into 3 periods: antecedent to flowering (09/10-18/10), the flowering (22/10- 01/12) and after flowering (27/12-05/01) and evaluated as transpiration. After the period of flowering the flow was more intense, but with no significant difference in the average. As the meteorological elements, radiation and relative humidity were the most determinant factors of transpiration.