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