INFLUENCE OF SOME ARTIFICIAL SUBSTRATES ON PRODUCTIVITY AND DRIS DIAGNOSIS OF GREENHOUSE TOMATOES (LYCOPERSICUM ESCULENTUM L. MILL., CV "VEDETTOS")

N. Rouin, J. Caron, L. Parent
Five artificial substrates were characterized for their porosity, air capacity and available water content and were evaluated in relation to yield and nutrient balance of tomato plants under spring greenhouse conditions in Quebec. On a volume basis, the substrates were composed of: 75% peat moss: 12,5% vermiculite: 12,5% perlite (pmPV); 60% spruce sawdust: 40% peat moss (Spm); 80% peat moss: 20% shredded hydrophobic rockwool (Rpm); 80% brown peat: 20% shredded hydrophobic rockwool (Rbp), rockwool slabs. Yield and DRIS nutrient balance were also compared between substrates used for one or two croppings.

Total porosity varied little among peat-base substrate (90–92%) but was higher in rockwool slabs (96%). Air capacity at 10 cm of water column was greatest in rockwool slabs (42%) but was relatively low in the pmPV medium. Easily available water between 10 and 50 cm of water column was lowest in the Spm medium at 17% and highest in rockwool slabs (52%). Considering total volume of substrate, however, a greater amount of easily available water was found in 56 L peat bags than in 11 L rockwool slabs.

A significant difference in tomato yield was found among substrates. Yield was highest in Spm, Rpm, and Rbp media used for a second crop. The greatest sum of DRIS indices was found in Spm used for one crop and yield proved to be correspondingly low. Marked P and N deficiencies in this substrate were attributed to N immobilisation by heterotrophic microflora and high pH limiting P availability. Plants grown in rockwool slabs produced intermediate yields as a result of higher water stress than in peat-base substrates, but index of nutrient imbalance was relatively small. Overall, in this experiment, the nutrient imbalance diagnosed by DRIS was not conducive to the yield standards of high-producing crops.

Rouin, N., Caron, J. and Parent, L. (1988). INFLUENCE OF SOME ARTIFICIAL SUBSTRATES ON PRODUCTIVITY AND DRIS DIAGNOSIS OF GREENHOUSE TOMATOES (LYCOPERSICUM ESCULENTUM L. MILL., CV "VEDETTOS"). Acta Hortic. 221, 45-52
DOI: 10.17660/ActaHortic.1988.221.4
https://doi.org/10.17660/ActaHortic.1988.221.4
English

Acta Horticulturae