Study On Mixed Seeding Experiment Of Alfalfa And Perennial Ryegrass Under Different Nitrogen Levels

Objective:High-quality forage is the material basis of animal husbandry.The problem of limited high-quality forage is a key problem to be solved urgently in the development of animal husbandry in XPCC.In view of this,it is of great practical significance to study the yield,nutritional quality,interspecific relationship and soil fertility of legume-grass mixed sowing in different proportions under the condition of nitrogen application,so as to provide theoretical basis for legume-grass mixed sowing in actual production,promote the efficient development of animal husbandry and increase the economy of farmers and herdsmen.Method:Alfalfa（WL525HQ）and perennial ryegrass（Toya）were used as materials,and a two-factor split-plot design was used.The nitrogen application rate was the main area,N₀:no nitrogen application;N₁:20%of the total nitrogen application rate was base fertilizer,20%of the topdressing at branching stage,and 60%of the topdressing at budding stage;N₂:20%of the total nitrogen application rate（100kg/hm²）was basal fertilizer,30%topdressing at branching stage and 50%topdressing at budding stage,with 3 replicates.The mixed sowing ratio was set as single sowing alfalfa（M）and perennial ryegrass（L）in the sub-region,and the sowing rates were 22.5 kg/hm² and 60.0 kg/hm²,respectively.Seven treatments were designed:alfalfa+perennial ryegrass 7:3（M₇+L₃）,alfalfa+perennial ryegrass 6:4（M₆+L₄）,alfalfa+perennial ryegrass 5:5（M₅+L₅）,alfalfa+perennial ryegrass 4:6（M₄+L₆）,alfalfa+perennial ryegrass 3:7（M₃+L₇）.Each plot was sowed according to the percentage of each single sowing treatment,with 3 replicates.A total of 21 treatments.For single sowing.The plot area was 20m²（4 m×5 m）,and the treatment spacing was 1 m.Results:（1）Under N₀,N₁ and N₂ nitrogen levels,the hay yield of mixed sowing ratio under different stubbles was significantly higher than that of single sowing（P<0.05）,among which the yield of L treatment was the lowest,and the N₁ nitrogen level was significantly the highest（P<0.05）.In the M₅+L₅ treatment,the total hay yield reached 1.06 t/hm²;under the mixed sowing ratio,CP,DM,RFV,TDN,and CP yield per unit area were the highest at N₁ nitrogen level,and NDF and ADF were the lowest at N1nitrogen level.Under N₀,N₁ and N₂ nitrogen levels,CP,DM,RFV,TDN and CP yield content per unit area were significantly higher than those of single sowing（P<0.05）,and NDF and ADF were significantly lower than those of single sowing（P<0.05）.Under the N1 nitrogen level,except for the M₇+L₃treatment,the CP content was significantly the highest（P<0.05）,and it increased first and then decreased with the increase of the proportion of perennial ryegrass.Among them,the CP content of M₅+L₅ treatment was the highest,the DM content of M₆+L₄ treatment was significantly the highest（P<0.05）,and the RFV and TDN of M₅+L₅ treatment were the highest（P<0.05）.The contents of NDF and ADF in M₅+L₅ treatment were the lowest（P<0.05）,and decreased first and then increased with the increase of the proportion of perennial ryegrass.（2）Under N₀,N₁ and N₂ nitrogen levels,the land equivalent ratio coefficient of different mixed sowing ratios was greater than 1,the relative yield of alfalfa was much greater than 1,and the relative yield of perennial ryegrass was far less than 1.With the increase of the proportion of perennial ryegrass,the relative total output value was greater than 1,and there was no significant difference under nitrogen level.The relative yield of alfalfa and perennial ryegrass was stable and the highest at N₁ level.The CP content of perennial ryegrass leaves was higher than that of stems by49%,the DM content of stems was higher than that of leaves by 19%,and the plant height of alfalfa was higher than that of perennial ryegrass by 69%.The nitrogen uptake and nitrogen utilization rate of perennial ryegrass increased gradually with the increase of proportion,and the nitrogen uptake and nitrogen utilization rate of M₃+L₇ treatment were significantly the highest（P<0.05）.Under the mixed sowing level,the indexes of nitrogen level were higher than those of non-nitrogen level,and the nitrogen level of N1 was the best.（3）Under the mixed sowing level,the physical and chemical properties of the soil at the nitrogen level were higher than those without nitrogen application,and the highest nitrogen level was N₁.The soil bulk density content of mixed sowing ratio was significantly lower than that of single sowing（P<0.05）.The soil water content,organic matter,total nitrogen content,alkali-hydrolyzable nitrogen,total phosphorus,available phosphorus,total potassium,available potassium and the number of nitrogen-fixing bacteria under N₁ nitrogen level were significantly higher than those of single sowing（P<0.05）.Although there was no significant difference in soil physical and chemical properties between mixed sowing ratios,the soil physical and chemical properties increased with the increase of perennial ryegrass ratio.Conclusion:（1）The mixed sowing of alfalfa and perennial ryegrass under different nitrogen levels had an effect on its nutritional quality,yield,interspecific relationship and soil stability.Among them,20%of the total nitrogen application rate（100kg/hm²）was used as base fertilizer,20%of topdressing at branching stage,and 60%of topdressing at squaring stage.When the mixed sowing ratio of alfalfa and perennial ryegrass was 5:5,the yield reached 1.06t/hm2,the crude protein content was 26.05%,and the NDF and ADF were 26.03%and 26.03%,respectively.（2）Under different nitrogen levels,the mixed sowing of alfalfa and perennial ryegrass made full use of forage resources,and had a certain niche separation and symbiotic relationship.At the same time,the mixed sowing increased the nitrogen absorption of forage,and the nitrogen utilization rate increased with the increase of perennial ryegrass proportion and was higher than that of single sowing.（3）The soil nutrients and the number of nitrogen-fixing bacteria under the nitrogen level were higher than those in the non-nitrogen soil,and were higher than those in the single-sown pasture.The content of organic matter and total nitrogen increased gradually with the increase of the proportion of perennial ryegrass,while the number of nitrogen-fixing bacteria increased first and then decreased,and the mixed ratio was the highest at 5:5.