| The 4 factors and quadratic general rotary unitized design molybdenum trial are carried out at Changning area of Datong county to find out the effect of nitrogen,phosphorus,potassium and sulphur on Medicago sative L..The result showed that,as the increasing of nitrogen,phosphorus,potassium dosage,the yield of Medicago sative L.increases at first and then decreases.The best fertilizer combination is urea 225 kg/hm2,calcium super phosphate 675 kg/hm2,Canadian potassium 225 kg/hm2,suphur 15 kg/hm2.At lower nitrogen soil,the Medicago sative L.yield increases as the increasing of phosphorus dosage,but it increase at first and then decrease as the increasing of potassium;at higher phosphors soil,there is not any obviously change as nitrogen increasing,it increases as potassium increasing.At higher phosphors soil,the yield don't change obviously as nitrogen increasing,while the combination of nitrogen and phosphorus fixed at certain level,the yield of Medicago sative L.increases at first and then decreases as another fertilizer factor increasing;at lower phosphorus soil,the yield of Medicago sative L.increases at first and then decreases as sulphur increasing,at higher phosphorus,the phosphorus increases gradually as sulphur increasing. |