Three densities(60000,75000,90000 plants/ha),three nitrogen application levels(150,225,300 kg/ha)and two chemical control treatments(no chemical control,chemical control)were set,and combined into seven cultivation patterns,including T1(high density,high nitrogen and ch...MORE Three densities(60000,75000,90000 plants/ha),three nitrogen application levels(150,225,300 kg/ha)and two chemical control treatments(no chemical control,chemical control)were set,and combined into seven cultivation patterns,including T1(high density,high nitrogen and chemical control),T2(high density,medium nitrogen and ...