Effects Of Intercropping Oat And Common Vetch And Nitrogen Application On Forage Yield,Quality And Water And Nitrogen Use Efficiency

Forage intercropping has been widely concerned in recent years.Intercropping of gramineous forage and leguminous forage can solve the problem of low yield of leguminous forage or low quality of gramineous forage.In addition,in the southern foothill of Yinshan,the precipitation is low and the seasonal distribution is uneven,so how to improve the water utilization rate of crops has become the main problem that researchers pay attention to.In this study,we used forage oats（Mengsiyan 1）and common vetch as materials,and carried out field experiments of after-oat intercropping combined with nitrogen application in the southern foothills of Yinshan Mountain from2020 to 2021.Set up three planting modes（P）（OV:Intercropping of oat and common vetch;MO:Monoculture oat;MV:Monoculture common vetch）and 3 nitrogen application levels（N）(N₀:0kg/hm²;N₇₅:75kg/hm²;N₁₅₀:150kg/hm²).The effects of different nitrogen application rates on the yield,quality,water and nitrogen use efficiency and soil characteristics of intercropping forage were studied,which provided a scientific basis for the cultivation management technology of efficient utilization of water and fertilizer for intercropping oat and common vetch in the southern foothills of Yinshan Mountain.The main research results are as follows:（1）The effects of planting pattern and nitrogen application level on the yield of fresh grass and hay were significant（P<0.01）.The yield of fresh grass and hay increased under different planting patterns with the increase of nitrogen application.Under the intercropping oat and common vetch N₁₅₀ treatment,the yield of fresh grass and hay was the highest.Compared with N₀,the yield of fresh grass and hay was increased by 42.23%and 50.59%in 2020 and 2021,and that of hay was increased by36.60%and 51.21%,respectively.The land equivalent ratio of intercropping of oat and common vetch was 1.07～1.15,suggesting that the intercropping of oat and common vetch had the advantage.（2）The contents of crude protein,ether extract and soluble sugar and their relative feeding value of oat and common vetch under different planting patterns were increased with increasing nitrogen application rate,while the contents of neutral and acid detergent fiber were decreased.The results showed that N₁₅₀ treatment had the best effect,but there was no significant difference compared with N₇₅ treatment（P>0.05）.（3）Planting pattern and nitrogen application level had significant effects on water use efficiency（P<0.01）.The soil water consumption and water use efficiency at growth stage of oat and common vetch increased with the increase of nitrogen application under different planting patterns.The soil water consumption under the intercropping oat and common vetch N₇₅ treatment in 2021 was the lowest,which was4.09%and 14.57%lower than that under the N₀ and N₁₅₀ treatments,respectively.In intercropping mode,the WUE under N₁₅₀ treatment was the highest in two years,which increased 48.95%and 10.63%compared with N₀ and N₇₅ treatments in 2020,and 37.24%and 3.45%compared with N₀ and N₇₅ treatments in 2021,respectively.（4）The effects of planting method and nitrogen application level on nitrogen content and nitrogen uptake of forage were extremely significant（P<0.01）.Under different cropping practices,nitrogen content and nitrogen uptake of oat and common vetch increased with the increase of nitrogen application,but the agronomic use efficiency,nitrogen uptake efficiency and nitrogen partial productivity of nitrogen were decreased under the nitrogen application level of N₁₅₀,and the highest nitrogen use efficiency was observed under the nitrogen application condition of intercropped oat N₇₅.Compared with N₁₅₀,the agronomic efficiency of nitrogen fertilizer in 2020 was increased by 42.98%,the nitrogen uptake efficiency of nitrogen fertilizer in 2 020 and2021 was increased by 28.21%and 21.43%,and the partial productivity of nitrogen fertilizer in 2020 and 2021 was increased by 71.73%and 54.30%,respectively.（5）Both planting pattern and nitrogen application level had effects on soil characteristics.Soil pH showed a decreasing trend with the increase of nitrogen application rate,and the soil pH was decreased by intercropping compared with monoculture.The lowest soil pH was 7.95 under the intercropping oat and common vetch N₇₅ treatment,which was 0.38%～3.40%lower than that under other treatments.The soil organic matter content showed an increasing trend with the increase of nitrogen application rate.In 2-year intercropping mode,the soil organic matter content in 0～20 cm soil layer was the highest in N₁₅₀treatment,which increased by 12.46%and15.61%in 2020 and 2021,respectively,compared with that in N₀.The contents of total nitrogen,alkali-hydrolyzed nitrogen,nitrate nitrogen and ammonium nitrogen showed an increasing trend with the increase of nitrogen application rate.The maximum total nitrogen content in 0～20 cm soil layer under the intercropping of oat and common vetch was found to be 50.89%and 4.76%higher in 2020 and 2021 than in N₀,respectively.The maximum soil alkali-hydrolyzed nitrogen content was found in the N₁₅₀ treatment,which was increased by 9.54%and 29.15%in 2020 and 2021 compared with N₀,respectively.Soil available phosphorus and available potassium showed an increasing trend with the increase of nitrogen application rate,and the content was higher in intercropping mode.The effects of nitrogen application level on soil microbial biomass carbon and nitrogen contents were significant（P<0.01）.With the increase of nitrogen application,soil microbial biomass carbon and nitrogen content showed an increasing trend,and all treatments were treated with intercropping oat and common vetch N₁₅₀,and the microbial biomass carbon increased by 109.25%and116.66%compared with N₀ in 2020 and 2021,respectively,and the microbial nitrogen increased by 393.22%and 289.95%compared with N₀,respectively.It was concluded that oat and green fertilizer common vetch had the effect of increasing soil fertility.（6）In terms of economic benefits,the net profit of the intercropping oat and common vetch model was higher（2544.44～5404.01 yuan/hm²）,and the highest monetary advantage index was 549.38 in the case of N₇₅.In conclusion,the intercropping oat and common vetch model can increase the forage yield of leguminous forage and improve the forage quality of grass in this region,and the water and nitrogen utilization efficiency under the nitrogen fertilization condition of N₇₅is better than that of N₁₅₀.The soil nutrient content and economic benefits of intercropping and nitrogen fertilization have been increased,which is suitable for widespread planting in the southern foothills of Yinshan Mountains.