24 Jan 2015

Effects of N and K rates on yield of summer Chinese cabbage in Chongqing

Chinese cabbage is one of the most widely year-round-grown leafy vegetables in China. Nutrient studies on Chinese cabbage conducted in the past were mostly targeted for winter varieties. Thus, the purpose of this project was to determine the optimal K rates for the summer varieties in the vegetable base of Chongqing. The experiment consisted of six treatments including two N rate (300 and 375 kg N/ha), one P rate (90 kg/ha) and four K rate (0, 75, 150 and 225 kg K2O/ha). The experiment replicated three times. Nitrogen was used as urea (N 46%), P as di-ammonium phosphate (N 11 % and P2O5 44%) and K as KCl (K2O 60 %). Nitrogen and K fertilizers were split into three times as basal application at seeding, topdressings at seedling and russet stages with proportions of 30:30:40, and P fertilizer was used once at seeding.

Results showed that at each N rate, cabbage yield increased significantly with an increase in K rates without leveling-off. At 225 kg K2O/ha, the highest cabbage yields reached 40.7 t/ha at 300 kg N/ha and 42.0 t/ha at 375 kg N/ha, which were 4.7 t (12.8%) and 5.9 t (16.4%) more than the K omission treatment. In terms of cabbage quality, the treatment with low N and low K combination obtained the higher contents of vitamin C, amino acids and soluble sugar, indicating high quality does not always go with high yield of the vegetable. The treatment with high N rate and medium K rate achieved the highest N agronomic efficiency and N recovery. Nitrogen contents in leaves dropped to the minimum at six days after topdressing, indicating that one week after topdressing may be the suitable time interval for the next fertilization during the fast growing period of the summer Chinese cabbage in the region.

More about: 西南地区