In order to clarify the suitable planting pattern and nitrogen application rate for rapeseed relay cropped rapeseed after wheat, a field experiment was conducted in Dalad Banner, Inner Mongolia. Five nitrogen application rate gradients (0, 30, 60, 90 and 120 kg/ha) were set under three planting modes, including straw removal+tillage (T1), straw returning+tillage (T2), and straw removal+no tillage (T3). The optimal nitrogen rate was determined based on rapeseed biomass, nutrient accumulation, and economic benefits. The results showed that the aboveground biomass, carbon accumulation and potassium accumulation of rapeseed under T2 treatment were all higher than those under T1 and T3 treatments. Under T2 treatment, the average of fresh grass weight, dry grass weight, carbon accumulation, and potassium accumulation of all nitrogen application treatments could reach 60.5 t/ha, 8.0 t/ha, 2981 kg/ha, and 253 kg/ha, respectively. Nitrogen application rate significantly affected the biomass and nutrient accumulation of rapeseed under different planting modes. The biomass and nutrient accumulation of rapeseed increased with the increase of nitrogen application rate within the nitrogen application rate range. Compared with no nitrogen application treatment, the fresh grass weight and dry grass weight of rapeseed increased by 39.8% and 35.1% respectively when the nitrogen application rate was 30 kg/ha, 63.0% and 67.9% at 60 kg/ha, 78.1% and 89.0% at 90 kg/ha, 86.5% and 98.1% at 120 kg/ha. The trend of nutrient accumulation of rapeseed green manure was basically consistent with that of biomass. The input costs and outputs of rapeseed for different purposes varied under different planting modes and nitrogen application rates. Considering the factors such as biomass, nutrient accumulation, and economic benefits of rapeseed for different purposes under different modes, rapeseed can be planted with no-tillage method with wheat straw removal following wheat harvest. The optimal nitrogen application rate for rapeseed as silage feed is 120 kg/ha, and for rapeseed as green manure, the optimal nitrogen application rate is 90 kg/ha.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |