Abstract
In summer Chinese cabbage cultivation, both tipburn and internal rot are very serious problems which are generally thought to be caused by calcium definiciencies attributable to a variety of environmental, physiological or nutritional factor.
Research was initiated by AVRDC soil science laboratory from 1983 to solve this serious obstacle and by 1985 a soil and crop management techniques had been developed which greatly reduces the tipburn and internal rot in summer grown Chinese cabbage in the tropics.
Tipburn was caused by NH4-N toxicity, limited root development, root damage, and rapid growth. Therefore, the following cultural practices are effective to reduce greatly tipburn: Avoiding NH4-N application at head intiation, increasing soil CEC and minimizing soil moisture fluctuation by compost application, water management and mulching, avoiding heavy application of fertilizer, suppressing the initial plant growth by covering outer leaves with rice straw and N split application.
On the other hand, internal rot was caused by limited Ca translocation into head leaves, vigorous growth rates and round-shaped heading cultivar. Therefore, foliar spray of citric acid, covering outer leaves before head formation, N split application, selecting of long headed cultivar and acceleration of rooting by water management are all effective ways of minimizing internal rot.
