Sigmoidal controlled-release fertilization improves nutrient recovery, nutrient balance, and environmental performance in Chinese cabbage

Purpose This study evaluated whether a sigmoidal controlled-release fertilizer could sustain Chinese cabbage productivity under reduced nutrient input while improving nutrient recovery, nutrient balance, and environmental performance under open-field conditions. Methods Field experiments were conducted in Korea in 2017 (Exp. I) and 2018 (Exp. II). Treatments included an unfertilized control, a conventional fertilization treatment, and three controlled-release fertilizer rates. Fresh yield, dry matter production, nutrient uptake, apparent nutrient recovery efficiency, plant nutrient balance, residual soil nitrate, and cumulative nitrous oxide emission were assessed to determine the agronomic-environmental optimum fertilizer rate. Results Compared with the conventional treatment, the 53 kg N ha − 1 controlled-release treatment reduced fertilizer input from 320 to 53 kg N ha − 1 , from 78 to 8 kg P 2 O 5 ha − 1 , and from 198 to 13 kg K 2 O ha − 1 , corresponding to reductions of approximately 6.0-, 9.8-, and 15.2-fold, respectively. Despite these reductions, this treatment maintained fresh yield comparable to the conventional treatment in Exp. I and produced the highest yield in Exp. II. It also showed substantially greater nitrogen recovery efficiency than the conventional treatment, reaching 87.2% and 82.6% in Exp. I and Exp. II, respectively, compared with 21.2% and 15.0%. In Exp. I, plant phosphorus-to-nitrogen and potassium-to-nitrogen ratios were lower under conventional fertilization, indicating less balanced nutrient acquisition. Cumulative nitrous oxide emission was highest in the conventional treatment (10.75 kg ha − 1 ), whereas the 53 kg N ha − 1 controlled-release treatment remained much lower (2.30 kg ha − 1 ) and similar to the unfertilized control. Conclusion The 53 kg N ha − 1 reduced input of sigmoidal controlled-release treatment was identified as the agronomic-environmental optimum because it maintained productivity while improving apparent nutrient recovery, nutrient balance, and selected environmental indicators under substantially reduced nutrient input. These results suggest that reduced input of sigmoidal controlled-release fertilization can be a practical strategy for more sustainable open-field Chinese cabbage production under the conditions of this study.