Effects of nitrogen application time and harvest time on seed yield and quality of Leymus chinensis

To determine the most appropriate nitrogen application time and harvest time for Leymus chinensis seed production in Heilongjiang Province, we studied the effects of different nitrogen application times (fertilized in the preceding autumn, current spring, or fertilized both in the preceding autumn and current spring) and harvest times (21, 24, 27, 30, 33, 36, 39, 42, or 45 days after the full flowering stage) on seed yield, impact factors (heading rate and seed setting), and seed quality (germination rate and thousand seed weight) of L. chinensis ‘Nongjing No. 4’. The results showed that nitrogen could significantly increase seed yield (P < 0.05) of L. chinensis. Additionally, nitrogen application, except fertilization during the current spring, could significantly increase heading rate and seed setting rate (P < 0.05). The heading rate, seed setting rate, and seed yield were the highest when nitrogen was applied during the preceding autumn and current spring compared to the other treatments. With the delay in harvest time, the seed yield, germination rate, and thousand seed weight first increased and then decreased. The seed yield, germination rate, and thousand seed weight harvested 33 days after the full flowering stage were all close to the maximum value. We suggest that the most appropriate nitrogen application time for L. chinensis was the preceding autumn and current spring and the optimal harvest time was 33 days after the full flowering stage in Heilongjiang Province.