Abstract
Recently, animal-waste composts have been extensively used for open culture systems according to area farming practices. This has resulted in the accumulation of specific nutrients and disruption of base balance. The study reports the accumulation of excess potassium and disruption of base balance due to extensive use of animal-waste composts as fertilizers at fields where black spots are frequently found in broccoli heads. In addition, the relationship between excess fertilization with potassium and development of downy mildew was observed. Excess fertilization with potassium decreased calcium and magnesium content in broccoli, decreased oxidation of lipid-like substances, and caused downy mildew. Thus, it was concluded that the major causes for the occurrence of black spots on broccoli heads in the production fields were excess accumulation of potassium and disruption of base balance due to extensive use of animal-waste composts. We speculate that the metabolism of the products was disturbed and the resistance to downy mildew might have lowered. It should also be noted that physiological disorders occur depending on the type of soil and products, and the growth process.
