Interactive effects of irrigation and nitrogen fertilizer on yield, nitrogen uptake, and recovery of two successive Chinese cabbage crops as assessed using 15N isotope

- Effects of irrigation and nitrogen fertilizer were evaluated in Chinese cabbage.
- Residue effects of N were assessed in the subsequent season.
- Dynamics of nitrogen derived from fertilizer were studied in two crop seasons.

The aim of this study was to evaluate the interactive effect of irrigation and nitrogen fertilization on yield, nitrogen (N) uptake, and recovery of two successive Chinese cabbage (Brassica campestris L.) crops and to assess the residue effects of N on the 2nd season crop under greenhouse conditions. 15N-labeled urea was administered to pot-grown Chinese cabbage in the 1st season. The cabbage plants were subjected to three irrigation treatments, 60 (W1), 75 (W2), and 90% (W3) of the soil field capacity, and four N rates, 0 (N0), 0.1 (N1), 0.2 (N2), and 0.3 (N3) g N kg−1 soil. The highest yield, dry matter (DM), N uptake, %Ndff (the percentage of N derived from fertilizer), N recovery rate, and the lowest loss rate were recorded in W3 treatment. N1 treatment had the maximum values for yield, DM, N recovery rate, and the lowest N loss rate. The highest %Ndff was recorded in N2 treatment, with no significant difference observed compared to N3 treatment in the 1st season. In addition, no significant difference among the N rates was observed in the 2nd season. Besides, roots exhibited higher %Ndff values than leaves. Only 5.30-23.00% fertilizer was absorbed by the Chinese cabbage, 56.22-71.29% remained in the soil, and 13.17-37.10% was presumably lost in the 1st season. The recovery rate in the 2nd season was approximately 3.51-17.40%. Therefore, in terms of yield, nitrogen recovery, and environmental impact, W3N1 treatment was recommended as the best combination for Chinese cabbage production and this treatment showed a productive potential in the 2nd season, as well.