6. Optimizing the Nitric Nutrition of Tomatoes cv. Rila F1, Grown in an Unheated Plastic Greenhouse, by Using Modified Granules which Contain Polymers and Black Sea Sapropelles

Nitrogen fertilization was optimized in early tomatoes cv. Rila F1 grown in an unheated greenhouse with modified granules, containing ammonium nitrate, Black Sea sapropelles and water swelling polymers. In variant (I), with granules coated with a polymer membrane of polyvinyl alcohol (PVA), the early yield (to 20.06.) was increased by 6.8%, while in variant (II) with granules possessing polymer membrane of partially acetylated PVA (PVA-M) the increase was 9.3%. The total standard yield of variant (I) was with 7.2% higher, while in variant (II) it was 13.78% higher compared to the control. The rate of fertilization with ammonium nitrate in variants I and II was reduced to 49.2 kg/da, compared to the control – 61.2 kg/da. An ecological effect is expected because of decreased pollution of the groundwater and plant production with nitrates due to a more even assimilation of ammonium and nitrate nitrogen.