Research article

Differences in N uptake and fruit quality between organically and conventionally grown greenhouse tomatoes

¹ Wageningen University, Department of Plant Sciences, Biological Farming Systems Group, Marijkeweg 22, 6709 PG Wageningen, The Netherlands
² Organic Foodstuffs Division, Faculty of Human Nutrition and Consumer Sciences, 02-776 Warszawa, Nowoursynowska 159c, Poland
³ Department of Agricultural Economics and Sociology, Andalusian Institute of Agricultural Research, IFAPA. P.O. Box 2027, 18080 Granada, Spain
⁴ North-East Agricultural University, College of Resource and environment, No. 59 Mucai Street, Xiangfang District, Harbin Heilongjiang Province, P.R. China
⁵ Wageningen University, Department of Plant Sciences, Horticultural Supply Chains Group, Marijkeweg 22, 6709 PG Wageningen, The Netherlands
⁶ Calle Francisco de Cuellar 451 casa 18 Monterrico, Santiago de Surco, Lima 33, Lima, Peru
⁷ Agriculture and Agri-Food Canada, Centre de recherche en horticulture, Pavillon Envirotron, Université Laval, Québec, QC, G1V 0A6, Canada
⁸ Department of Plant Pathology and Emerging Pathogens Institute, University of Florida, Gainesville, FL32611, USA

^* Corresponding author: gravelv@agr.gc.ca

Accepted: 18 May 2010

Abstract

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 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.