Study On Fertilization Responses Of High Efficiency Production Of Alfalfa In The Irrigation Area Of Hexi

Hexi area is one of the alfalfa advantage producing areas in northwest China.In this area,the soil is relatively poor,and the scientific management measures of fertilization and evaluation method of economic benefit are lack,and fertilization is blind,and the fertilizer utilization rate is low.Therefore,the efficiency and sustainable development of grass husbandry in Hexi area is restricted.In this study,alfalfa in high yield period（1-5 years after planting）was taken as the research object in Hexi irrigated area.The"3414"incomplete orthogonal regression design（nitrogen（N）,phosphorus（P）and potassium（K）are 3 fertilization factors）was adopted to systematically analyze the production performance,fertilizer effect and economic benefits of alfalfa under different N,P and K fertilizers by the fixed-point fertilization experiment for 5consecutive years.The purpose of this study is to explore the effect of alfalfa fertilizer under high efficiency production in Hexi area,and to provide reference for nutrient management and economic benefit evaluation in high yield year of alfalfa.The results are as follows:1)The effect of production performance,quality and soil nutrients on fertilization of alfalfa.Fertilization can significantly increased he yield and cumulative growth height of alfalfa,but decreased the stem-leaf ratio of alfalfa.In the 5th year,alfalfa yield was the highest when P,K and N fertilization were applied at 105 kg·hm^-2,45 kg·hm^-2 and 51.75 kg·hm^-2（P2K1N1）,respectively.Under P2K1N1,the cumulative total yield of alfalfa in 5 years reached 98947.62 kg·hm^-2,which increased by 40.99%compared with non-fertilization treatment.The following treatments were P₁K₂N₁treatment(P 52.5 kg·hm^-2,K 90 kg·hm^-2,N 51.75 kg·hm^-2)and P₂K₂N₂treatment(P 105kg·hm^-2,K 90 kg·hm^-2,N 103.5 kg·hm^-2),and the 5-year cumulative yields were 97455.34kg·hm^-2 and 97091.03 kg·hm^-2,respectively.Fertilization can significantly increase the crude protein content and total protein content,reduce the ADF and NDF content,and significantly increase the relative feeding value,and improve the soil nutrient status of alfalfa.Among them,the total protein content of alfalfa was the highest level(17682.57 kg·hm^-2 accumulated in 5 years),the relative feeding value was reached the super-level（158）,and the soil nutrient enhancement effect was the most obvious when the fertilizer amount was P₂K₂N₂treatment(P 105 kg·hm^-2,K 90 kg·hm^-2 and N 103.5 kg·hm^-2)2)Study on balanced fertilization model of alfalfa in Hexi irrigation areaIn the 4th year of planting,the effects of N,P and K on grass yield and total protein yield was P>K>N.The interaction effect of N,P and K on yield was shown as N-K>N-P and>P-K,and the main interaction effect on the total protein yield was N-P.This study simulated the ternary quadratic fertilizer effect function of grass yield and total protein yield in the 4th year of alfalfa planting.The recommended N,P and K fertilization rates for achieving the target grass yield of alfalfa were 71.53-86.40 kg·hm^-2,68.07-83.00 kg·hm^-2,63.49-75.94kg·hm^-2,and total target protein yield of alfalfa were 68.21-80.44 kg·hm^-2,83.03-95.47kg·hm^-2,64.15-75.19kg·hm^-2,respectively.In the 5th year of planting,the contribution of N,P and K n grass yield and total protein yield was P>N>K.The interaction effect of N,P and K on yield was shown as P-K>N-K>N-P and the main interaction effect on the total protein yield was mainly the N-P.The ternary quadratic fertilizer effect function of grass yield and total protein yield in the 5th year of alfalfa planting.The recommended N,P and K fertilization rates for achieving the target grass yield of alfalfa were68.41-80.95 kg·hm^-2,68.47-79.95 kg·hm^-2,68.64-80.32kg·hm^-2,and total target protein yield of alfalfa were 77.64-86.67 kg·hm^-2,80.41-93.04kg·hm^-2,72.51-83.31kg·hm^-2,respectively.3)Evaluation of the economic benefits under balanced fertilization of alfalfaThrough the data envelopment analysis of economic benefits of alfalfa planting for 1-5 years,it was found that when the ratio of P,K and N fertilizer was 105 kg·hm^-2 90 kg hm^-2and 103.5kg·hm^-2（P₂K₂N₂）,the economic benefit was the best,which was DEA effective.When alfalfa was not fertilized（P₀K₀N₀）,respectively.Its economic benefit was the lowest and its adjustment range was the largest,followed by no phosphorus treatment（P₀K₂N₂）and no nitrogen application（P₂K₂N₀）.This also confirms the importance of balanced fertilization to alfalfa production in Hexi irrigation area from theperspective of economic benefits.The influences of N,P and K fertilizers on the economic benefit of alfalfa in 1-5 years were as follows:In the 1st year of planting,N fertilizer had the greatest influence,and P fertilizer had the greatest influence on the economic benefit in the 2nd to the 5th year of alfalfa.In the comprehensive 5 years,P fertilizer had greater influence on the economic benefit than N and K fertilizers of alfalfa.