We aimed to compare, with minimum error, the quality of cabbages (Brassica oleracea L. var. capitata) cultivated with continuous application of chemical or organic fertilizer in fields from 2002 to 2010. To this end, we studied the influences of reduction of sample size, sample weight, and degree of plant growth in each treatment on the quality of cabbage. ① We found that constituent composition varied throughout the cabbage sphere. Therefore, it was necessary to obtain the representative aliquot for the analysis of nitrate and other constituents. ② In the 11th planting, many qualitative characteristics (such as head density, L-ascorbic acid content, and nitrate content) were found to be correlated with the head weight of samples. Thus, the need for comparison of samples with equal weight, not simply representative weight, was confirmed. ③ For most analyzed characteristics, small differences were observed between cabbages subjected to the 2 manure treatments with different degree of growth, only when the samples compared were of equal weight. By using these sampling methods, we compared the quality of cabbages cultivated with continuous application of chemical fertilizer or manure. On comparison of samples of representative weights, we found that the cabbages cultivated using manure had greater spheroidicity, dry matter and L-ascorbic acid contents, with lower head density and nitrate content. However, significant differences were found only in spheroidicity, head density, and nitrate content (only at the 11th planting) between cabbages subjected to the 2 treatments, when comparing samples with equal weights.
