THE EFFECT OF WARM ROOT ZONE TEMPERATURES ON GROWTH OF TOMATO AND POINSETTIA

With the high cost of fossil fuel it has become imperative for greenhouse operators to incorporate heat saving techniques. One method for conserving fuel is the use of solar energy as a heat source. A solar heated greenhouse has been designed at Rutgers, which makes use of the floor as a storage and heat exchange area. This results in the root systems of plants grown on the floor being warmed.

Experiments in which tomatoes were grown under warm rooted conditions indicate that growth and total yield are increased when compared to plants grown in conventional hot air heated greenhouses. Lowering the night temperature slowly to 7.2°C in conjunction with warm root zones resulted in vegetatively larger plants than those grown under 15.5°C night temperatures without root warming. However, the sub-optimal night temperature grown plants produced a greater number of misshappen fruits. Therefore, it appears the tomato cultivars that used warm floor conditions could not overcome the deleterious effect of cool night temperatures.

Poinsettia plants grown at warm root zone temperatures developed bracts sooner than plants grown without root warming. Also the plants were shorter and fuller, eliminating the need for growth regulators when grown with warmer roots.

It is apparent that the growing conditions in the Rutgers style solar greenhouse is beneficial to both vegetable and ornamental crops.