Investigations were carried out in 2008-2010 on Chinese cabbage (Brassica rapa L. var. pekinensis (Lour.) Olson). The main problem in cultivation of this vegetable is physiological disorder – tipburn. It is connected with low level of calcium in young leaves and with water deficiency. In 2008, seeds of Chinese cabbage were sown twice, in April and July. In July, the day temperature was high (25-30 °C) and relative air humidity was low (35-50%). In these conditions, the young leaves were injured heavily. Rotting was caused by the activity of bacteria Pectobacterium carotovorum subsp. carotovorum (Jones) Hauben et al. However, three times foliar application of 1.5% calcium nitrate or 1.5% Wapnovit significantly reduced the tipburn. Also spraying with 0.03% of Tytanit (containing ions of titanium) or with 2.5% of Biochikol 020 PC (containing chitosan) gave similar effect. In these conditions, application of 1.5% K-300 (containing potassium oxide and ammonium nitrate) exacerbated symptoms of tipburn. Application of Wapnovit or Tytanit reduced instantly rotting of heads contrary to the application of their mixture. In autumn cultivation, when the relative air humidity was 80-100%, spraying with 1.5% solution of K-300 significantly decreased injuries in comparison to control. Application of Wapnovit, K-300, Biochikol, Tytanit or the mixture of Biochikol and calcium nitrate eliminated rotting. In experiments done in the springs of 2009 and 2010, when weather conditions were less favorable for tipburn appearance, a severity of it was lower but application of K-300 increased it appearance. In these experiments, Biochikol and Wapnovit eliminated rotting of heads. The results of three years of study have shown that calcium nitrate, Wapnovit, Tytanit and Biochikol limited occurrence of tipburn and bacterial rotting of Chinese cabbage, but the weather conditions during cultivation had the greatest impact on the severity of tipburn.
