Effect of Root Restriction on the Performance of Three-Truss Cultivated Tomato in the Low-Node Pinching Order at High-Density Cultivation System

Abstract

The low-node pinching order at a high-density plant cultivation system (LN&HD) is now widely adopted for increasing tomato yield and fruit quality. The LN&HD cultivation period spans 70–120 days, employs the use of a small amount of substrate (low substrate volume), and plants are usually topped between the first and the fourth truss. Using a small amount of substrate in cultivation induces root restriction. Increasing the extent of root restriction in small pots has been adopted for increasing the fruit quality of tomato in some advanced countries. However, improving fruit quality at the expense of yield becomes a major drawback for adopting the LN&HD in Ghana. The LN&HD was introduced into Ghana mainly to increase tomato yield sustainably at a cost-effective level. This study aimed to manipulate or reduce the extent of root restriction to increase tomato yield. Information related to manipulating or reducing the extent of root restriction has not been extensively reported. Thus, an experiment was conducted (between 21 April 2019 and 11 August 2019) in the greenhouse of the University of Ghana Forest and Horticultural Research Centre, Kade-Ghana. Plants of two tomato cultivars (Jaguar and Momotaro York) were subjected to four root restriction conditions. The extent of root restriction were (1) complete root restriction in a 1.0 L volume capacity pot, (2) complete root restriction in a 1.5 L volume capacity pot, (3) partial root restriction in Rockwool-like cultivation, otherwise referred to as Cocowool, and (4) No root restriction in a trough containing 1.5 L of the substrate. The experiment was laid out in a 2 x 4 factorial in a randomized complete block. Results showed that partial root restriction in Cocowool and unrestricted roots in the trough produced the highest tomato yield and total dry matter compared to the plants that received complete root restrictions in the 1.0 and 1.5 L pots. However, the tomato’s total soluble solids increased with a complete root restriction in the 1.0 L pot. Reducing the extent of root restriction increased the yield and total dry matter of tomato. With the LN&HD, a small amount of substrate could be used (at a reduced cost) with a partial root restriction to increase the yield of tropical tomato cultivars grown in Ghana.