Hydroponic tomatoes with brown bottoms

by Dave
(Perth, Western Australia)

I have been growing hydroponic tomatoes for many years using proprietory AGROW nutrient with no problems. This year I changed from the small cherry variety to a much large variety. Plant growth was good with plenty of flowers, however I had to hand pollinate as I lost a lot of flowers due to lack of bee activities. I used an old shaving brush and soon found that flowers were setting fruit.

Recently I noticed some plants had black bottoms, and thought it may have been a bug, but on examination could find not insect activity. Minor white cabbage butterfly caterpillar activity was observed and an occasional small brown moth.

The two tanks each hold 10 plants and the nutrient is pumped around using 900 litre tanks running 15 minutes every hour between 7 am and 6 pm daily. The area is bounded by fencing and part of the rear of the house and virtually totally enclosed overhead with shade cloth, which precludes most pests.

Having read this feed, it's obvious that the plants are calcium deficient. I will check the maker and seller for their comments. However, it could be that I am running a too weak solution for the larger variety of tomato than previously grown. I may increase the ratio.