The Response of Broccoli and Cabbage to Soils with Different Fertilization Histories

The purpose of this study was to investigate the growth, nitrogen (N) uptake and distribution, nitrate nitrogen (NO3(superscript -)-N) content of broccoli and cabbage as affected by different fertilizers, grown in soils with different fertilization histories. The field used in this study is located in Chi-san, at the Kaohsiung District Agricultural Improvement Station, in Southern Taiwan. The soils in this study were subjected to long-term studies, and were treated with organic fertilizer only (OF), chemical fertilizer only (CF), or a combination of organic and chemical fertilizers (IF), all of which were applied continuously. After transplantation, broccoli and cabbage plants were harvested at 75 and 70 days, respectively. The plants were separated into roots, leaves (wrapper leaves for cabbage), and heads. After drying to a constant weight at 65℃, the dry weight, nitrate N, total N, and insoluble N were determined, respectively. The results showed that the growth and N uptake of broccoli and cabbage from the OF-treated plot were the same or even higher than those from the CF and IF plots. The N use efficiency (NUE) for the OF plot was also higher. The NO3(superscript -)-N concentrations of both the entire broccoli and cabbage that received OF treatment were lower than those which received CF treatment. The total N and soluble N concentrations of organic fertilizer-treated broccoli were lower than those of the chemical fertilizer-treated ones; the reverse was true for cabbage. In conclusion, after 11 years of applying organic fertilizer and establishing the soil fertility, the crop yield of OF treatment, in which the application of N fertilizer was based on the mineralization capacity, can be as high as or higher than that of CF treatment, resulting in lower NO3(superscript -)-N concentrations in the plants.