Balanço de energia e evapotranspiração do tomateiro em ambiente protegido.

Abstract

The knowledge on growth of cultivated species allows to planning and to manage, in a rational way, the cultivations, contributing so that the species get to express ali its potential, besides supplying data for construction of mathematical models capable to describe the need of water by crops, through the knowledge of evapotranspiration. The main objective of this work was the energy and hydric characterization in the development of tomato kaki in greenhouse, seeking determination of the need of water. The following determinations were performed: sensitive and latent heat flows by the methods of energy balance of Bowen and by the method of Penman-Monteith; crop coefficient through the methods of Linacre, Penman-Monteith and radiation; and evapotranspiration by the methods of water balance and Penman-Monteith. During the experimental period, weekly measures of plants height and length and width of leaves were taken. Models were adjusted for determination of the foliar area index, in function of the width and length of the leaves. Compared to the model of Penman-Monteith, the model of Linacre underestimated the values of ETo, when the radiation balance (Rn) was superior to 7.0 MJ m" ; on the other hand, when Rn happened in the strip of 4 MJ m"2 the method of Linacre overestimated ETo. The radiation balance was consumed in 71% by the latent heat flow inside of the greenhouse, and in 15% by the sensitive heat flow. In spite of the behavior of the two methods be the same, the values found by the water balance method were larger than the ones found by the method of Penman- Monteith. The relationship Rgi and Rge stayed constant during the cycle with transmissivity of 89%, showing, therefore, reduction of 18%, provoked by the covering of polyethylene. The Rg, in spite of showing a high agreement, presented a larger error when compared to the other elements, showing that significant differences exist among the measures obtained inside of the greenhouse and the ones estimated by the externai data. The mean value of fruits per plant was of 21.5, with a production of 3.04 kg plant"1 and a productivity of 7.6 kg m"2, totaling a productivity of 76 t ha"1, which is a value larger than the National mean. It was verified that the largest water consumption happened in the reproductive phase.