The Effect of Chloride on Yield and Nutrient Interaction in Greenhouse Tomato (Lycopersicon Esculentum Mill.) Grown in Rockwool

The effect of increasing chloride content in nutrient solution on nutrient composition in root environment, interaction of nutrients in leaves and yield of greenhouse tomato cv. ‘Grace F ₁’ grown in rockwool were searched. In Experiment I (2004–2005) the levels of 15, 30, 60, and 90 mg Cl·L ⁻¹ but in Experiment II (2006) 30, 60, 90 and 120 mg Cl·L ⁻¹ of nutrient solution were tested. The sources of chloride were water (9.6–10.7 mg Cl·L ⁻¹) and calcium chloride (CaCl ₂·2H ₂O) but the rest of nutrients and sodium in all treatments were on the same levels. It was found that increasing content of chloride from 15 to 60 mg Cl·L ⁻¹ enhanced the total and marketable fruit yield. Within the range of 60 to 90 mg Cl·L ⁻¹ the yield was on the optimum level but the content of 120 mg Cl·L ⁻¹ declined it. Increasing chloride content in the nutrient solutions was reflected in rising of chlorine content in leaves. The concentration of chloride above 60 mg C·L ⁻¹ reduced the content of nitrogen but above 90 mg C·L ⁻¹ declined the content of calcium, sulfur and zinc in leaves. The antagonism between Cl:N, Cl:Ca: Cl:S and Cl:Zn was appeared. More variable interaction were between Cl:K and Cl:B. At the low levels of chloride, from 15 to 60 mg Cl·L ⁻¹, potassium and boron content were decreased but at the higher ones, from 90 to 120 mg·L ⁻¹, these nutrients had increasing course. It was not found out the effect of chloride contents on macro and microelement contents in nutrient solution emitted from drippers however their content upraising in root medium (rockwool). The highest increase was found out for Na 95.1 and 64.9 % (Exp. I and II - respectively), next for Ca (76.0, 70.1 %), Cu (62.5 and 71.0 %), Cl (43.6, 24.4), B (33.3, 21.0 %), N-NO ₃ (30.4, 49.6 %), Zn (29.5, 32.8 %), S-SO ₄ (25.9, 25.5 %), K (24.5, 24.1 %), Fe (19.8, 19.2 %), Mn (17.5, 21.3 %) and Mg (14.9, 11.7). Advantageous effect of chloride on tomato yield justified the need to introduce for the practice adequate chlorine nutrition, and recommend to maintain 60 to 90 mg Cl·L ⁻¹ in nutrient solution. The best yield appeared when content of chlorine in leaves (8th or 9th leaf from the top) was in the range 0.48-0.60 % of Cl in d. m.