| Alfalfa（Medicago sativa）has the characteristics of high nutritional value,wide range of planting application and strong selenium enrichment ability.Therefore,it is of great practical significance to explore the enrichment rule of exogenous selenium-enriched foliar fertilizer of alfalfa,which can directly or indirectly supplement selenium for animals and human body.In this study,different concentrations of selenium-rich foliar fertilizer（sodium selenite,Na?Se O3）were applied to alfalfa and different spraying methods（spraying frequency,spraying interval,spraying solution amount）were applied to investigate the effects of different spraying treatments on the growth characteristics,yield,selenium content and nutrient composition of alfalfa.In order to obtain the optimal spraying scheme for selenium-rich alfalfa production,the comprehensive evaluation and economic effect evaluation of alfalfa quality in harvest period were carried out to provide theoretical basis for selenium-rich alfalfa production.The results are as follows:（1）When the concentration of foliar selenium fertilizer（in terms of Se）was 11.25～90.0 mg/m2,the plant height（PH）,stem thickness（SD）and biological yield weight（BW）of alfalfa at the harvest stage increased first and then decreased with the increase of selenium concentration.When the selenium concentration was 56.25 mg/m2,PH,SD and BW reached the highest values,which increased by 10.8%（P<0.05）,18.4%（P<0.05）and24.94%（P<0.05）,respectively compared with the control group.The selenium content of alfalfa during harvest was positively correlated with the selenium concentration（R2=0.9575）,and when the selenium concentration was 90.00 mg/m2,the selenium content was11.69 mg/kg,an increase of 1184.62%（P<0.05）compared with the control group,and the selenium growth accumulation（GA-Se）was up to 10.62 mg/m2 at 56.25 mg/m2,an increase of 1261.54%（P<0.05）compared with the control group,at which time the selenium fertilizer utilization rate（UR-Se）is 17.65%.The selenium concentration mainly affected the CP and EE content in the nutritional components of alfalfa,CP content was the highest at a selenium concentration 45.00 mg/m2,at 19.06%;EE content was the highest at a selenium concentration of 90.0 mg/m2,at 2.06%.（2）Under the premise that the total selenium concentration was 33.75 mg/m2,the p H,SD and BW of alfalfa at harvest were significantly higher in the selenium-rich foliar fertilizer spraying of 2 sprays treatment and 3 sprays treatment than those in the control group（P<0.05）,and the content of alfalfa selenium in the 2 sprays treatment and 3 sprays treatment were significantly higher than that in 1 sprays treatment and the control group,which increased by 474.73%（P<0.05）and 492.31%（P<0.05）,respectively,and the GA-Se in the 3 sprays treatment was 5.38 mg/m2.The CP content of alfalfa in the 2 sprays and 3sprays treatments was significantly higher than that in the control group（P<0.05）,and the highest content was 18.28%in the 2 sprays treatment.（3）Under the premise that the total selenium concentration was 33.75 mg/m2,the p H and SD of alfalfa at harvest in the 5 days treatment and 7 days treatment were significantly higher than those in the control group（P<0.05）.The BW in the interval 5 days treatment and the interval of 7 days treatment was significantly higher than that in the interval of 3days treatment（P<0.05）.The selenium content in the interval of 5 days treatment and the interval of 7 days treatment were significantly higher than that in the control group and the interval of 3 days treatment,increasing by 530.77%（P<0.05）and 507.69%（P<0.05）.The US-Se in the interval of 5 days treatment and interval of 7 days treatment was significantly higher than that in interval of 3 days treatment（P<0.05）.Different interval treatments mainly affected the CP content of alfalfa nutrient composition at harvest time,and CP content in the interval of 5 days treatment and interval of 7 days treatment were higher than that in the control group（P<0.05）,and the highest was 18.16%in the interval of 5 days treatment.（4）Under the premise that the total selenium concentration was 33.75 mg/m2,The p H and BW of 75 m L/m2 treatment and 100 m L/m2 treatment were significantly higher than those in the 50 m L/m2 treatment and group（P<0.05）,and the SD of 75 m L/m2 treatment group was significantly higher than that in control group（P<0.05）.The selenium content and US-Se in the 75 m L/m2 treatment were the highest,which increased by 518.68%（P<0.05）and 628.21%（P<0.05）,and there was no significant difference in CP content（P>0.05）between the three spray solution treatments of foliar selenium fertilizer,which was higher than that in the control group（P<0.05）.In this study,a principal component analysis system was constructed to evaluate the quality of alfalfa by combining the growth characteristics,yield,selenium content and nutritional indexes of different treatment groups.The primary component analysis showed that the selenium application concentration was the highest at 56.25 mg/m2.When the total selenium concentration was 33.75 mg/m2,the quality of alfalfa was better than that of other treatments,the interval of 7 days treatment was better than the other interval treatments,and the single spray solution 75 m L/m2 treatment was better than other solution treatments.The results showed that the optimal spraying scheme for the production of selenium-rich alfalfa was a total selenium concentration of 56.25 mg/m2,divided into 2 sprays with an interval of 7 days,and the amount of solution per spray was 75 m L/m2.According to the optimal spraying scheme for the production of selenium-rich alfalfa obtained by the above research,the economic effect evaluation through test data,field demonstration data and market price data,the results show that the input-output ratio of selenium-rich alfalfa produced under the optimal spraying scheme is 1:4.39,which can effectively improve the economic benefits. |
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