CALCIUM NUTRITION AND CULTIVAR INFLUENCE INCIDENCE OF TIPBURN OF COLLARD

The collard (Brassica oleracea, Acephala group) cultivar Vates was more susceptible than 'Blue Max' to tipburn in sand-culture and field studies. Calcium concentrations in young leaves were similar for both cultivars. 'Blue Max' appears to require a lower Ca concentration in young leaves than 'Vates' for normal growth. In sand-culture studies, increasing the Ca level in nutrient solution to 3 mM or higher decreased tipburn in 'Vates'. 'Blue Max' did not develop tipburn regardless of Ca level. Increasing the Ca level in nutrient solution increased Ca concentration in young and old leaves for both cultivars. Soil application of CaSO4 or foliar application of Ca(NO3)2 or CaCl2 did not decrease occurrence of tipburn in 'Vates', presumably because these treatments did not increase Ca concentrations in young leaves.