SUBSTANTIAL REDUCTION OF WATER AND NITROGEN SUPPLY DOES NOT NEGATIVELY AFFECT QUALITY OR YIELD OF ORGANICALLY GROWN TOMATOES

Tomato (Solanum lycopersicum L. ‘Cauralina’) plants were grown organically in a plastic tunnel, from 30 March to the beginning of August 2011. From mid-May, four treatments were applied: high water supply/high nitrogen (W+/N+), reduced water supply/high nitrogen (W-/N+), high water supply/low nitrogen (W+/N-) and low water supply/low nitrogen (W-/N-). Irrigation was triggered beginning on 20 May to keep water tension between 10-30 cbars in the W+ treatments, and 30-50 cbars in the W- treatments.
In the N+ treatments, 10 kg N ha^-1 × 4 was supplied, while no N was supplied during the cropping season in the N- treatments.
Water supply was reduced by 23% at the end of the trial in the W- treatments, whereas the nitrate content of plants and maximal photosynthesis were not significantly modified in the N- treatments.
By contrast, from mid-June, chlorophyll content was found to be lower in the N- treatments.
Midday leaf water potential and stomatal conductance were lower only from the end of June in the W- treatments.
Leaf net photosynthesis, respiration, yield, mean fruit mass, fruit taste and concentration in organic acids were not modified by the treatments.
In the W+/N- treatment, fruit harvested on 4 August contained more reducing sugars (+ 13%) and vitamin C (+ 35%) than the W+/N+ fruit.
There was also a 15% increase in vitamin C in the fruit of the W-/N- treatment when compared with W-/N+ fruit.
Our observations suggest that it is possible to reduce irrigation and nitrogen supply in organic tomato crops without any negative effect on yield and quality.

II International Symposium on Organic Greenhouse Horticulture

J.B. Mazzitelli, F. Lopez-Lauri, S. Laurent, V. Vidal, L. Urban, H. Gautier, L. Gomez, G. Vercambre, S. Sérino, C. Mazollier

greenhouse, irrigation, organic farming, secondary metabolism, stress

https://doi.org/10.17660/ActaHortic.2014.1041.10