Articles
INFLUENCE OF DIFFERENT SURPLUS IRRIGATION AND SUBSTRATE ON PRODUCTION OF GREENHOUSE TOMATOES
Pannovy) were studied.
Furthermore two substrates (burned clay and clay granules) with different water capacities were tested.
The plants were grown in a recirculating irrigation system with 5 L substrate per plant.
Irrigation was done in every surplus treatment by equal number of impulses per day (4–39, depending on irradiation) and equal impulse duration (2–4.5 minutes, depending on growing stage). The different percentages of surplus were reached by changing the amount of nutrient solution per impulse.
Compared to the lowest surplus, permanent irrigation increased the marketable yield in burned clay from 6.0 to 12.8 kg/m2 and in clay granules from 11.0 to 14.9 kg/m2. Also the fruit diameter, was positively affected in both substrates by higher surplus irrigation.
The total number of leaves and the leaf area of the youngest twenty leaves were influenced positively only in burned clay (lower water capacity). Plants grown in clay granules showed no significant reaction, but the leaf area was constantly on a comparable high level.
In both substrates the root development was better in high surplus treatments, which could be caused by a decreasing salinity in the container.
In the reflux nutrient solution for K, Ca and Mg over three times the concentration of the flow pipe solution was found in low surplus treatments.
These concentrations decreased with higher surplus to an acceptable level.
In low surplus treatments low Ca-concentrations were found in the leaves.
These concentrations clearly increased with higher surplus corresponding to the decreasing concentration of K (K/Ca-antagonism).