CONCLUSIONS
Climatic conditions strongly influenced yield, water economics and nutrition. In the warm season, yield was significantly reduced, more water per plant was required which meant more leachates and higher spending in fertilizers, and there were moreproblems with blossom end rot despite unusually high Ca2+ concentration in the leaves.
The use of a closed irrigation system allowed savings of water and fertilizers in the order of 30%. However, problems with attack of Clavibacter michiganensis subsp. michiganensis with coir as substrate, reduced fruit yield in the warm season, compared to the open system.
Use of coir as substrate in open system helped to reduce water supply to plants and cost of fertilizers from 20 to 30% compared to volcanic scoria, with no reductions in yield. This is an important issue provided the huge amounts of water used, and the large amount of fertilizers required, to maintain high yields in greenhouse tomato.