Soil-bound intensive greenhouse production has been scrutinized for its sustainability due to contamination of ground water by
over-fertilization resulting in leaching of nutrients. As environmental guidelines are becoming more restrictive worldwide, and especially in
Europe, many greenhouse growers have converted to more sustainable production systems including rockwool culture with recycled water and
organic cropping systems in soil. The increase in popularity of organic production systems has amplified the debate whether organically grown
produce is healthier than conventional produce. So far, little is known about the variations in fruit quality associated with production systems
for greenhouse grown tomatoes. Thus, two organic (organic fertilization with and without straw amendment) and three conventional tomato
cropping systems (regular and increased nutrient solution in rockwool and regular fertilization in soil) were compared in order to evaluate
differences in nutrient availability and effects on fruit quality over a three-year period. Three modern medium-sized round tomato cultivars and
one old cultivar were compared. There were no significant interactions between cropping systems and cultivars, so that main effects of systems
and cultivars could be evaluated. Fruit yields in the organic systems were similar to those obtained in the conventional soil-bound system, but
15% lower than in the regular rockwool system, even though nitrogen concentrations in soil were not limiting in any of the production systems.
Frequent organic amendments resulted in higher soil NO2−
3 contents in the organic system without straw than in the other soil-bound systems,
indicating that the organic systems were not yet stable in terms of nutrient availability after three years. A fruit quality index, based on the
contents of compounds such as lycopene, β-carotene and vitamin C, was similar in all cropping systems. The old cultivar had a significantly
higher quality index, but a lower yield than the other cultivars. According to this study, high quality tomatoes can be obtained through proper
adjustment of the quantity and the source of nitrogen fertilizers in organic and conventional cropping systems and the use of selected cultivars
with a high nutrient use efficiency for organic systems.