Optimization of the water application in greenhouse tomatoes by introducing a tensiometer-controlled drip-irrigation system

Abstract

This article deals with the results of a water-application experiment on greenhouse tomatoes ( Lycopersicum esculentum Mill.) in a temperate climate. The irrigation experiment conducted during 4 successive growing-seasons comprised, in addition to handling according to classical water application (i.e. non-controlled standard watering), 2 treatments in which the water was applied by means of a tensiometer-controlled drip-irrigation system. Both treatments with the drip-irrigation system differ from each other in the critical suction tension maintained in the root zone at a depth of 15 cm, a pF of 1.9 (the “wet”) and a pF of 2.2 (the “dry”) treatments, respectively. The water-application pattern exhibited a definite connection with the corresponding time course of the evapo-transpiration in the wet tensiometer-controlled treatment as opposed to that in the classical. The total irrigation volume in the dry tensiometer-controlled treatment was seriously reduced as compared to the wet. The moisture tensions in the plow layer continued to fluctuate within certain margins in both tensiometer-controlled drip treatments, without outstanding peaks. During the time which elapsed, some differences between the spring and autumn crops were noticed, particularly in the dry treatment. With respect to yield, there was no mutual difference between the tensiometer-controlled treatments, neither qualitatively nor quantitatively. This consequence arises primarily because the water deficit in the dry moisture level can be compensated for by capillary ascent from the phreatic surface. With the exception of the autumn crop of 1980, the yield in the tensiometer-controlled treatments was consistently better than in the control. The difference was not always equally significant in the matter of total yield, but it was certainly significant with regard to gradation and primarily with regard to average fruit weight.