Diagnosis and prevention of tea leaf etiolation of young trees planted in brown soil of Shandong Province

The physiological disease, leaf etiolation, can easily occur in young tea trees planted in brown soil with higher pH value (＞6.5) in Shandong province. All leaves of some trees turned yellow, some leaves of new shoots turned white to a certain extent or had some brown spots on the yellow leaf margin. The tea trees with this disease grew weak, which restricted the tea garden to be formed. In order to identify the pathogen of this disease, the pH, organic matter content and nutritional conditions of the soil and six mineral elements related to leaf color in diseased tea leaves were analyzed, and the fertilizers including N, Mg, Fe, Mn, Cu and Zn were spraying on the diseased tea leaves to test the effect of cure the disease. The results indicated that the etiolation cause of the substrate mature leaf was the deficiency of available nitrogen in the soil. Spraying urea on the yellow leaves can turn the color of substrate mature leaf to green, but it does not have such effect on new shoots. The etiolation cause of new shoots was the deficiency of manganese and cuprum contents, and spraying microelements of manganese and cuprum on the new shoots can prevent and cure this disease. The mechanism of manganese and cuprum deficiencies need to be further investigated.