Maintaining High Yield and Improving Quality of Non-Heading Chinese Cabbage Through Nitrogen Reduction in Different Seasons

Non-heading Chinese cabbage (Brassica rapa L. ssp. chinensis) is an important vegetable crop. In its production, the excessive application of chemical fertilizers is common, resulting in increased production costs and decreased quality. Therefore, exploring appropriate nitrogen (N) application amounts is essential. Here, we investigated the effects of a single application of different gradients of N fertilizer on the growth, yield, and quality of cabbage by setting eight N fertilizer treatments, specifically, 0, 1, 2, 4, 6, 8, 10, and 12 kg/6.67 × 10−2 ha. We found a positive correlation between the N application amount and the yield in different seasons and a negative correlation with nitrate. The relationship between the yield of cabbage and the N application amount in three seasons was consistent with y = −ax2 + bx + c (a > 0), and the corresponding fertilizer application rates for the highest yields in spring and autumn were predicted to be 9.3 and 8.4 kg/6.67 × 10−2 ha, which was reduced by 19.1% and 30.0%, respectively, compared with conventional application rates. In addition, after two consecutive N fertilizer reductions, the second crop plants did not reduce significantly under each treatment. While, compared with the first crop, the second crop plants grew weaker with lower flavor quality and yield, they also had higher nitrate contents. In conclusion, appropriate but not excessive N reduction was beneficial in obtaining high-yielding and high-quality non-heading Chinese cabbage in spring and autumn.