§ Squadron-Leader Donnerasked the Under-Secretary of State for Air if he will state in some detail why the concrete runways of unused airfields have been considered unsuitable for hydroponics.
§ Mr. T. Williams:For hydroponic cultivation a large volume of water containing mineral salts must be circulated twice daily through sand or gravel in the tanks in which the crops are grown; and the provision of large water holding tanks and pumping machinery, as well as the sand or gravel, is consequently necessary. The capital outlay is therefore high, and the system is only suited for high priced vegetable crops where the climate is suitable, markets are readily accessible and the water supply is abundant. The existence of a ready made concrete base for die tanks would not be of importance in comparison with these other considerations.