The analysis of the state of vegetable growing in hotbeds and greenhouses made by the Scientific Research Institute and the study of 40 state farms in the Central non chernozem zone showed the obvious advantage of greenhouse and hotbed combines of an area exceeding 30 decares (1 decare = 0.10 ha). The yield in the big combines is higher by 15 per cent on the average, the prime cost of the produced vegetables is 44 per cent lower and the labour input is 3–4 per cent less compared with the smaller combines.
The combines located in the southern parts of the country provide greater yields during the autumn, winter and spring periods.
Thus for instance, the average cucumber yield in the first and fourth quarters is 1.3 kg/m2 or 6.3 per cent of the total yield in one of the best Moscow greenhouse-hotbed combines - the Marfino State Farm - and in the State farm No. 1 situated in the region of Adler city the yield for the same period reaches 8 kg/m2 or 43.6 per cent of the total yield.
The yield of greenhouse-grown tomatoes near Moscow in the first and fourth quarters is lower while in Adler, Tashkent, Kislovodsk 34–40 per cent of the total amount of fruits is obtained during these periods.
From the point of view of economic solution of engineering and construction problems of hotbed and greenhouse construction the southern regions have the advantage.
Building constructions there are considerably lighter owing to the small snow accumulations as a result of which their cost diminishes.
The sharp reduction in the envisaged temperature difference cuts heating costs and the comparatively high mean temperatures of the outside air and the considerable solar radiation curtail the expenses for heating the plant-growing structures.
Based on these investigations, a suggestion was put forth to combine the development of vegetable growing in the open with that in hotbeds and greenhouses in the South with a view to supplying the more northern regions with vegetables.
In recent years numerous investigations were carried out to perfect the hydroponic method of growing vegetable crops.
Cultivars have been chosen, schemes worked out for the size and configuration of the nutrient area, substrates selected, the technology of using the substrates and solutions is being developed and specified.
This progressive method of raising vegetable crops ensures the production of 18–20 kg/m2 cucumbers, 8–14 kg/m2 tomatoes and cuts labour input by 17–40 per cent.
The collaborators of the Institute for Vegetable Growing studied the root nutrition of cucumber plants grown in hotbeds on artificial medium.
It was found that during the first year the use of keramsite as a substrate