Objectives The paper studied the yield and nitrogen loss caused by fertilization rate and combination proportions of manures with chemical fertilizer, to provide a theoretical basis for efficient use of different organic manures in the area.

Methods A winter wheat/summer maize rotation field experiment was conducted in Yucheng Experimental Base of Chinese Academy of Agricultural Sciences, Shandong, from October 2014 to September 2015. The tested wheat cultivar was Jimai22 and maize cultivar was Zhengdan958. In the conventional nitrogen application rate of N 225 kg/(hm²·season), chemical fertilizer (CF), chicken manure (CHM), pig manure (PM) and cattle manure (CM) were applied in different chemical and manure N ratios (0%, 25%, 50%, 75%, 100%). In addition, single application of double N rate of fertilizers (DCF, DCHM, DPM and DCM) and no fertilizer control were included in the experiment. The crop yields, N₂O emission and NH₃ volatilization flux were determined.

Results In the N rate of 225 kg/hm², the 100%CHM and 100%PM treatments had similar yields with 100%CF, but 100%CM treatment produced lower yields. Compared with their conventional N rate, DCF, DCHM and DPM had similar yields, while DCM increased maize yield significantly. The yields of wheat and maize in different proportion treatments of pig and chicken manure were all similar to those of 100%CF, and there was no significant difference among them. While among the combining treatments of cattle manure with chemical fertilizer, wheat yield decreased with the increasing ratios of cattle manure, and maize yields were less affected by the ratios. In N rate of 225 kg/hm², 100%CF treatment had an annual NH₃ volatilization of 39.63 kg/hm², which was 37–53 folds greater than those of 100% CHM, PM and CM treatments. The NH₃ discharge coefficient in 100%CF was approximately 9%, while those in the three 100% manure treatments was only 0.2%. The total annual NH₃ volatilization quantities of organic manure with chemical fertilizer were increased significantly with increase of chemical fertilizer ratio. When the chemical fertilizer accounted for 75%, the total annual NH₃ volatilization quantity was similar to that of 100%CF. Applying double N rate of CF, PM, CHM and CM all increased the annual NH₃ volatilization significantly. NH₃ volatilization occurred mainly during wheat season in manure treatments while mainly during maize season in CF treatments. The total annual N₂O emission for 100%CF was 2.85 kg/hm², higher than those of 100% manure treatments. The total annual N₂O emission of the manures were in the order of pig manure (2.51 kg/hm²)>chicken manure (1.91 kg/hm²)>cattle manure (1.85 kg/hm²). The average N₂O emission in the double N rate treatments was more than 1.5 times of those in conventional N rate. When the chemical fertilizer accounted for 50%, the total annual N₂O emission quantity was similar to or higher than those of 100%CF. The N₂O discharge coefficient for 100%CF was around 0.4%, while those for 100% manures were only about 0.3%. The NH₃ and N₂O emission was mainly occurred during wheat season in 100% manure treatments, whereas that was mainly during maize season in 100%CF. The NH₃ and N₂O emission quantities in double N rate treatments were significantly increased, but the discharge coefficients were kept the same.

Conclusions Manure sources and nitrogen combining proportions with chemical fertilizer perform significanly different on crop yields, N₂O emission and NH₃ volatilization. Under the conventional N rate, chicken and pig manure could be applied alone or combined with a proportion of less than 50% of total N, while cow manure could be applied combined with more than 75% of chemical nitrogen, to achieve the similar crop yield as with chemical fertilizer alone, and reduce the gaseous loss of nitrogen fertilizer in farmland.