To optimize the management practices during the transition period "Grain for forage" in North China

the production potentials of biomass and crude protein and the ammonia (NH3) emissions under 4 different rotations were investigated with field experiment. A field experiment including 5 crop rotations was conducted

of which the traditional winter wheat-summer maize rotation (W-SuM) was considered the reference to evaluate the production potentials of biomass and crude protein in other rotations such as ryegrass -summer maize (R-SuM)

ryegrass-spring maize (R-SpM)

ryegrass-double summer maize (R-DM) and double summer maize (DM)

and their NH3 emissions were also measured in situ with Draeger-tube method (DTM). Results indicated that among the 5 crop rotations

the R-DM rotation had the greatest biomass (31 012 kg/hm2) and crude protein (2 529 kg/hm2) production

which were 14.3% and 8.2% greater respectively than those in the W-SuM rotation. The annual NH3 volatilizations from these rotations ranged from 13.43 to 23.77 kg/hm2

accounting for 4.2%～5.6% of their N applications

which were both in an order of R-DM＞W-SuM＞R-SpM＞R-SuM＞DM. Meanwhile

the seasonal distributions of NH3 emissions under different rotations differed

e.g. the contribution of NH3 volatilization in summer season in DM rotation was much greater than those in other rotations. The ryegrass-double summer maize rotation was high likely to produce the greater biomass and crude protein.