Effect of variety choice and use of resistant rootstock on crop yield and quality parameters of tomato plants grown in organic, low input and conventional production systems/growth media

Summary

Soil-borne diseases are one of the most important problems in organic and other ‘low input’ soil-based greenhouse production systems. While chemical soil disinfection has been the method of choice in conventional farming systems, soil steaming has been the main strategy for the control of soil borne diseases in organic production. Both methods are extremely expensive and have been increasingly restricted for environmental reasons by government and organic standard setting bodies respectively.
The use of tolerant varieties and of grafting onto resistant rootstocks were evaluated as potential replacements for soil steaming in organic and low input systems and found to be as effective in reducing root disease and increasing root fresh weight, fruit yield and number. The effects on fruit yield and quality characteristics were then further evaluated using different varieties for grafting and different growth media typically used in (a) organic (soil amended with manure), and (b) conventional (perlite fertilised with mineral fertilisers via the irrigation system) growth media/fertilisation regimes, and also a (c) novel “low input” growth medium designed to provide better aeration of the rooting zone. Fruit numbers, diameters and weights and total fruit yields were significantly different between growth media and highest for plants grown in the “low input” system, slightly lower for plants grown in the perlite and lowest for plants grown in the organic system. The potential for replacing chemical and steam soil disinfection methods in organic and ‘low input’ soil based greenhouse production systems is discussed.