Effect of Nitrogen and Ccalcium Concentration in Nutrient Solution on Growth, Yield and Tipburn of Butterhead Lettuce in Floating System

The present investigation was carried out to evaluate the impacts of different concentrations of N and Ca and N:Ca ratio in nutrient solution on growth indices, yield and tipburn of butterhead lettuce ( Lactuca sativa var. Capitata) in floating system. The experiment was conducted as completely randomized design, with 8 treatments and 3 replications, in Research Greenhouse of Shahrekord University. Treatments (different concentrations of Ca and N (mg/L) in the nutrient solution) included T 1 (N60 + Ca80), T 2 (N80 + Ca80), T 3 (N100 + Ca80), T 4 (N120 + Ca80), T 5 (N120 + Ca160), T 6 (N160 + Ca160), T 7 (N200 + Ca160) and T 8 (N240 + Ca160). Results showed that there was no significant difference between treatments for number of leaves; but significant differences were observed in tipburn percent, leaf and root fresh weight, leaf and root dry weight, and stem length and diameter. The highest head weight, length and diameter of stem, and root and leaf dry weight were observed in T 1 (N60 + Ca80), T 2 (N80 + Ca80) and T 3 (N100+ Ca80) treatments. The weight of head in different treatments varied from 218 to 326 g/plant. Increasing the N concentration to more than 100 mg/L decreased the yield. Higher yield was obtained in 80 mg/L Ca concentration as compared to 160 mg/L. The tipburn occurrence of the treatments varied from 10.5 to 42.5 percent. The lowest tipburn occurrence was observed in T2 and T6 (N:Ca=1) treatments; while it was highest in T1 and T5 (N:Ca=0.75) treatments. Leaf analysis showed that significant difference was observed among the treatments with respect to N and Ca content. The T2 treatment (N80 + Ca80) was the best due to its high yield and lower tipburn incidence.