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Accueil du site Doctorat Chine 2018 Study on the Construction of Alfalfa Fertilizer Model and Physiological Mechanism of Nutrient Efficiency in the Arid Irrigation Area of Northwest China

** Titre : ** Study on the Construction of Alfalfa Fertilizer Model and Physiological Mechanism of Nutrient Efficiency in the Arid Irrigation Area of Northwest China

** Auteur : ** 于铁峰；

** Grade : ** Doctoral Dissertation 2018

** Université : ** Gansu Agricultural University

**Résumé **

The arid irrigation area in northwest China is one of the important pasture production areas.Because of the lack of management means and the blindness of fertilization,the soil nutrient elements was lack and imbalance,and the low utilization rate of nitrogen,phosphorus and potassium fertilizer caused the yield and quality of alfalfa(Medicago sativa)not to reach the standard of high-quality forage.So this study took the alfalfa(2 years in 2016 and 3 years in 2017)in the northwest arid irrigated area as the study object,the effects of different fertilization systems on alfalfa production performance,carbon and nitrogen metabolism,root nodule nitrogen fixation,soil nutrient characteristics and soil microbial characteristics were systematically studied by using the quadratic regression 3414 experimental design and single factor experiment design,and the relationship among fertilizer,crop,soil and microorganism was also analyzed.Moreover,the mechanism of nutrient absorption and utilization in high-yielding alfalfa field was revealed,and the fertilizer efficiency model of alfalfa(Gannong No.3)production in the northwest arid irrigated area was established,and the optimum amount of fertilizer was also obtained.The main results were as follows:The results showed that the contribution of N,P and K to the yield of two years old alfalfa was K > P > N,and the contribution of N,P and K to the yield of three years old alfalfa was P > K > N,and the interaction effect in two years old alfalfa was N-P > N-K > P-K,and the interaction effect in three years old alfalfa was N-K > N-P > P-K.The contribution of N,P and K to the total protein yield of two years old alfalfa was N > K > P,and the contribution of N,P and K to the total protein yield of three years old alfalfa was N > P > K.The effect of N-P interaction on the two years old alfalfa was better than that of N-K interaction and P-K interaction.The effect of N-P interaction and N-K interaction on the total protein yield of three years old alfalfa was significantly greater than that of P-K interaction.By using the method of frequency analysis,the optimal fertilization amount of N,P and K were 56.27 67.51 kg·hm-2,77.69 90.48 kg·hm-2 and 76.43 87.18 kg·hm-2 when the target yield of the two years old alfalfa was higher than the average yield of 17522.1 kg·hm-2,when the target yield of three years old alfalfa was higher than the average yield of 19234.1 kg·hm-2,the optimal fertilization amount of N,P and K were 46.75 57.66 kg·hm-2,80.15 92.28 kg·hm-2 and 57.79 69.74 kg·hm-2,respectively ;when the total target protein yield of two years old alfalfa was larger than the average of 2115.7 kg·hm-2,the optimal fertilization amount of N,P and K were 66.35 77.48 kg·hm-2,79.34 98.87 kg·hm-2 and 73.68 85.38 kg·hm-2,respectively ;when the total target protein yield of three years old alfalfa was larger than the average of 2656.0 kg·hm-2,the optimal fertilization amount of N,P and K were 68.44 79.50 kg·hm-2,72.74 85.96 kg·hm-2 and 50.68 61.61 kg·hm-2,respectively.Soil pH decreased after harvest of alfalfa without fertilization,soil organic matter content for all treatments increased,and increased by 9.31% 14.93%.Soil total nitrogen was not affected by fertilization and alfalfa planting years ;N,P,K was benefitial for the increase for soil available nitrogen,available phosphorus and available potassium,respectively.

** Mots clés : ** alfalfa； fertilization model； carbon and nitrogen metabolism； nodule nitrogen fixation； microbial biomass； soil enzyme；

Page publiée le 12 avril 2019