Nitrogen Recovery and Transport Efficiency of Winter Rapeseed and Residual Nitrogen Effect on Subsequent Sesame using 15N Labelling Technique
In China, the application rate of nitrogen in rapeseed is high, but the uptake and utilization efficiency is low, which may cause irreversible environmental pollution. Use of efficient nitrogen rate and to improve nitrogen recovery, transport and residues management is important for crop productivity and sustaining the environment. Therefore, a pot was conducted using two winter rapeseed cultivars of Huayouza No.9 (HZ9) and Huashuang No.5 (HS5) under two N levels (0.15-N1 and 0.30-N2 g N.kg–1 soil). The 15N-uera was applied before sowing (basal) and at stems elongation stage (topdressing). The results indicated that 15N recovery efficiency (15NRE) of HS5 under N1 increased by 5.89 percentage points compared to N2, and the most obvious difference was observed in grain. However, no significant difference was observed in HZ9 between the two N levels. The 15N transport efficiency (15NRE) of the N1 treatment (37.62~37.70%) was much higher than that of the N2 treatment, with the difference mainly observed in stem (4.33~5.03%). The 15NTE of basal was significantly higher than that of topdressing, with the difference mainly found in leaves (14.02~19.52%). The 15NRE under topdressing treatment (56.85~61.60%) increased 8.18 and 8.58 percentage points relative to that under basal treatment, with the main difference observed in grain and pericarp. Additionally, about 1.62% nitrogen from rapeseed season in two N levels was absorbed by the subsequent sesame crop, with its yield increased by 26.00~89.19% compared to the control. The average 15NRE of sesame from basal and topdressing was 1.91% and 1.34%, with a yield increase of 16.22% and 59.50% over the control, respectively. The integrated data indicated that higher N recovery and transport efficiency can be achieved by adequacy reducing application rate and increasing the proportion of topdressing, and the residual soil nitrogen of rapeseed can be recovered to some extent by planting sesame.