Effect of Different Intensities of Leaf Removal on Tomato Development and Yield

Abstract

Defoliation (leaf removal or pruning) is a common practice in tomato production that makes crops more manageable, prevents conditions conducive to fungal attack and increases the exposure of the fruit to light, especially in winter conditions. The intensity and frequency of leaf removal on commercial farms often vary according to workforce availability criteria, which makes it difficult to determine their effect on tomato crop yields. It would be reasonable to think that a reduction in leaf area influences radiation interception and, therefore, the production of assimilates and biomass. However, in intensive production systems with a high leaf area index (LAI), leaf pruning can increase radiation interception, either by reducing competition between productive and vegetative organs or by increasing radiation use efficiency. This study was therefore designed to assess the effect of different intensities and frequencies of basal leaf removal on dry matter production and partitioning between the different organs of the plant, and thus on tomato crop productivity. A series of trials were conducted over three consecutive seasons, with a trial conducted per season: (a) Trial 1: leaf removal control—LRC (with leaves removed from the base to two leaves below the truss close to harvest, T0) was compared with LR1 (leaf removal from the base to two leaves below the truss above T0, i.e., T1) and LR2 (two trusses above T0 (T2)); (b) Trial 2: LRC compared with LR2 and LR4 (four trusses above T0 (T4)), carried out at two frequencies; and (c) Trial 3: LRC compared with an intense leaf removal treatment (LRI) whereby between 10 and 12 leaves were left on each stem. LAI saturation values under our conditions were found to be around 2.0. No significant differences in yield were found between the control and treatments LR1, LR2 and LR4, with a reduction in the number of leaves of up to 35% and LAI values during harvest above 2.0. The intense leaf removal treatment (LRI), which reduced the number of leaves by 47% and the LAI value from 2.8 to 1.5 compared to the control, resulted in a 15% reduction in dry biomass and a 17% decrease in fruit yield.