Effects Of Selenium And Cobalt Fertilizers On Growth And Quality Of Alfalfa

As the most widely used high quality leguminous grass, alfalfa(Medicago sativa L.) has an important role in feed production and processing in our country. Selenium and cobalt, important trace elements in the growth of alfalfa, have an inimitable effect on improving the yield and quality, promoting photosynthesis, antioxidation and biological nitrogen fixation of alfalfa root microorganism. Meanwhile, alfalfa is natural selenium-rich plants, with high absorption and storage capacity of selenium, so alfalfa is an excellent carrier to organizing inorganic selenium. Northern pasture is an important alfalfa production and processing base in China, has lower content and validity of selenium and cobalt in soil, causing deficiency of selenium and cobalt in alfalfa, therefore, it can be relieved through the application of selenium and cobalt fertilizer.This experiment takes Medicago sativa L. vc. Gannong No. 3 as material, study on the effect of selenium and cobalt fertilizer on the seed germination, growth characteristics, grass production, quality and root by germination and pot in poor test.Understand the application effect and determine the best fertilizer rate of selenium and cobalt, the purpose of this is intended to prove definite theoretical basis about application of fertilizer in alfalfa planting process in northwest region.The results showed that:⑴Selenium and cobalt solution can promote the germination of alfalfa seed, improve the germination energy, germination percentage, germination index and vigor index of seed. With the increase concentration of selenium and cobalt solution, each index increased first and then decreased, in the condition of 10℃, the best seed germination was LT-15 treatment, germination energy, germination percentage, germination index and vigor index of seed were 68.00%, 85.33%, 132.87 and 3.33 respectively, in the condition of 20℃, the best seed germination was NT-12 treatment, germination energy, germination percentage, germination index and vigor index of seed were 79.67%, 91.67%, 140.21 and 3.61 respectively.⑵In the single test of selenium and cobalt, with the increase application rate of selenium and cobalt fertilizer, grass production, nutritional contents and relative feeding value of alfalfa increased first and then decreased in the first year. With selenium 2.5 mg/pot, hay and fresh yield were highest in S3 treatment, which were 11.79 g/pot and 49.96 g/pot respectively, with selenium 3.5 mg/pot, crude protein, crude fat, crude ash and relative feeding value was highest in S4 treatment, which were 19.97%, 5.74% and 9.29% respectively, neutral detergent fiber and acid detergent fiber was lowest in S4 treatment, which were 34.93% and 27.08% respectively. If use high content of crude protein, crude fat, crude ash and low content of neutral detergent fiber and acid detergent fiber for the evaluation standard of alfalfa quality, S4 treatment was the best and C6 treatment was the worst.⑶In the mixing experiment of selenium and cobalt, the numerical values about plant height, growth rate, grass production, crude protein, crude fat, crude ash, underground biomass and root morphology of alfalfa were increased first and then decreased with the increase of fertilizer rate, stem-leaf ratio, neutral detergent fiber and acid detergent fiber were just opposite, decreased first and then increased in the first year. According to the average value of each index of the two crops, the content of stem-leaf in S3C2 and S3C3 treatment were the same optimal, which were 1.02, underground biomass, relative feed value, root volume, bifurcation number were highest in S3C2 treatment, but neutral detergent fiber and acid detergent fiber were lowest, which were 2.6258 g, 186.06%, 2.05 cm3, 34.28% and 26.23% respectively. Plant height, growth rate, hay and fresh yield, crude protein, crude fat, main root length, root surface area and root diameter were highest in S3C3 treatment, which were 51.56 cm, 1.04 cm/d, 172.88 g/pot, 43.88 g/pot, 19.98%,6.09%, 25.33 cm, 137.68 cm2 and 1.16 mm respectively. There were very significant positive correlation among root traits, root dry weight and aboveground biomass(P<0.01). S3C3 treatment was recommended as the best fertilizer rate of selenium and cobalt which was 5.0 mg/pot and 0.8 mg/pot respectively.