Articles
INFLUENCE OF SOME ARTIFICIAL SUBSTRATES ON PRODUCTIVITY AND DRIS DIAGNOSIS OF GREENHOUSE TOMATOES (LYCOPERSICUM ESCULENTUM L. MILL., CV “VEDETTOS”)
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 (9092%) 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.