DEPTH OF SOIL CULTIVATION AS AN INFLUENCING FACTOR ON CROP YIELDS OF GREENHOUSE TOMATOES

Development and crop yields of greenhouse tomatoes are largely due to the size of the plant root system. A shallow rooting of plants - often occurring in greenhouse tomato production - is in most cases the result of certain properties of the soil. If the bottom level of the soil layer tends to be packed, the root system can not develop normally into the ground and its size is considerably reduced.

In the experiments the effects of two different depth levels of soil cultivation were investigated on earliness and amount of the yield. Two combinations were made in the experiment: 1. 25 cm deep cultivation of soil, and 2.50 cm deep cultivation of soil.

The ploughing up to 50 cm was made only in the 80 cm wide beds for 2 plant rows. At first the whole ground in the greenhouse was ploughed to a depth of 25 cm, and then disinfected by steaming. The experiments were founded on the method of randomised blocks. They were established in three replications. Ten plants were set out for one plot. There were 4 plants in 1 m2 area planted after the double-row method, 90x50x35 cm. The plots for shallow cultivation were ploughed 25 cm one more prior to sowing. Mineral and organic fertilizing applied in the experiments was the same for the plots of both combinations.

The experiments were carried out in a spring culture of tomatoes (variety Potentat) in the seasons of 1964/65, 1965/66 and 1966/67, as well as in an autumn culture in 1966 and 1967 (same variety).

The plants in the spring and in the autumn culture were pruned to a single stem and in the spring culture their tops were pinched out above the 7th cluster. During the growing season spring tomatoes were top-dressed with mineral fertilizers five times and the autumn tomatoes four times. These top-dressings were carried out at equal intervals of 12–14 days; the first top-dressing was applied at the flowering of the 4th or 5th cluster.

Fruits were picked out twice a week, only ripe ones. Till 1 June fruits were sorted as commercial of the diameter above 35 mm and those above 40 mm in accordance with the standard thereafter.

Dates of some agricultural techniques are shown in table 1.

The particular treatments were performed at different dates in the various years of the experiments. The differences are small and did not effect the results (table 2).

According to findings, deep cultivation of soil showed to have a good effect on the production of greenhouse tomatoes. Higher yields are obtained of spring tomatoes, even though in the case of autumn tomatoes significant differences in favour of the deep cultivation of soil were obtained.

A considerable increase of the early crop amounting to 14–25% of the