Excessive application of fertilizer nitrogen (N) in crop production systems in the North China Plain (NCP) has resulted in the accumulation of nitrate (NO3-) in subsoil. Denitrification is a possible pathway for removal of accumulated nitrate in subsoil. But denitrification is often neglected and/or regarded as unimportant because of the low amounts of metabolizable carbon in most subsoils. The aim of the study is to evaluate the priming effect of glucose (G) application on denitrification in a 0-190 cm soil profile in a winter wheat/maize double cropping system. The study was conducted at Luancheng Agroecosystem Experimental Station, Chinese Academy of Sciences. The experiment had four treatments in triplicate: CK (0 kg N and G ha-1 year-1), N (750 kg N and 0 kg G ha-1 year-1), CCK (0 kg N and 4000 kg G ha-1 year-1) and CN (750 kg N and 4000 kg G ha-1 year-1).
Results/Conclusions
Our results indicated that application of glucose significantly promoted denitrification rates with N addition. The total amounts of N losses via denitrification in 0-190 cm soil profile were 4.2, 4.4, 19.4 and 35.9 kg N ha-1yr-1 in CK, CCK, N and CN, respectively. Specifically, we highlighted that 37% of the total denitrification activity in 0-190 cm soil profile in N occurred at 0–15 cm top soil layer, 19% occurred at 15-90 cm soil layer and 44% occurred in the soil layer beneath the root zone (90-190 cm). The removed nitrate via denitrification in CN increased 130%, 95% and 28%at 0-15 cm, 15-90 cm and 90-190 soil layers, respectively. In conclusion, we found that the subsoil (15-190 cm) was a large contributor to nitrate losses via denitrification. Meanwhile, metabolizable carbon addition is an effectively potential pathway to remove accumulated nitrate in subsoil in a winter wheat/summer maize double cropping system in NCP.