Abstract:

To investigate the effects of reduced nitrogen application combined with organic fertilizer on the rice-wheat rotation system，six treatments were set up：no potassium（NP），conventional fertilization（N100），15% nitrogen reduction based on conventional fertilization（N85），30% nitrogen reduction based on conventional fertilization（N70），15% nitrogen reduction based on conventional fertilization with organic fertilizer（MN85），and 30% nitrogen reduction based on conventional fertilization with organic fertilizer（MN70）. The results showed that compared with N100，MN85 significantly （p<0.05）increased the biomass of rice and winter wheat by 5.5% and 16.2%，respectively，and significantly increased potassium uptake in wheat grains and straw by 23.4% and 63.6%，respectively. Potassium fertilization increased straw potassium content and alleviated soil potassium deficit，but reduced internal potassium efficiency，and combined application of organic fertilizer decreased the partial factor productivity of potassium fertilizer. Compared with NP，MN85 significantly increased soil available potassium content，while no significant changes were observed in total potassium or slow-release potassium among treatments. In conclusion，15% nitrogen reduction combined with organic fertilizer performed best in both yield improvement and potassium balance，but attentions should be paid to the potassium release characteristics of organic fertilizer and the sustainability of soil potassium pool for the long-term application.

Key words: rice-wheat rotation, reduced nitrogen fertilization, organic fertilizer, potassium uptake, soil potassium supply capacity