In the central zone of the European territory of the Soviet Union vegetable growing in the open is restricted to a period of two to four months.
However, through the use of heated areas, hotbeds and plastic sheet covers, this period can be prolonged to five-six months.
Vegetables can be grown year-round in heated glass greenhouses.
Hence, an increase in the frost-protected areas is of paramount importance for supplying such big cities like Moscow, Leningrad and other industrial centers with fresh vegetables.
Belaya Dacha state farm operates on the basis of utilizing the heat produced by industrial enterprises.
Up to 1966 the farm has used the heat waste of the Moscow Oil Refinery, this being paid 90 kopeiki the megacalorie.
The utilization of this kind of heat-supply source by the farm proves expedient and effective despite the fact that in 1965 only 3.5 hectares of greenhouses were supplied with heat, in order to keep them in operation throughout the winter.
Along with the increase in greenhouse areas, vegetable yields have also increased from 20 kg per unit area in 1958 to 40 kg at present.
The state farm grows 10 vegetable cultivars: 3 cucumber, 5 tomato and 2 cauliflower.
During the last 12 to 15 years special attention has been paid to the use of hybrid seeds.
Cucumber and tomato heterotic cultivars have been widely adopted.
Of the cucumber cultivars most suitable have proved those developed by the Higher Institute on Plant Growing (VIR) and its experimental stations.
They are VIR 1, VIR 2 and Uspeh 221 heterotic cultivars.
The Institute has developed 10 new hybrid cucumber cultivars for hotbeds, greenhouses and plastic sheet protected growing, and one tomato hybrid for greenhouse production.
A number of cucumber hybrids have been developed at the Crimea and Maikop experimental stations of the Institute on the basis of the partially dioecious Posrednik 97, Izobilnij 131 and Plodovitij 147 cultivars.
The seed-production system developed by the Institute has been applied to the cucumber and tomato cultivars grown in the mentioned plant-growing structures.
The mass propagation of first reproduction seeds is being carried out by the All-union enterprise Sojuzsortsemovosht on open areas in the southern regions of the country, where favourable conditions for this production exist.
For the production of intervarietal hybrid cucumber and tomato seeds the superelite and elite plants of the parental cultivars are grown in plant growing structures.
Direct hybrid seeds production from the parental cultivars is carried out in the open in the southern regions of