Research on Decline Law and Recovery Technique of Astragalus adsurgens Meadow on Kerqin Sand Land Application of molecular identification techniques in Chinese materia medica Rooting Depth of Alfalfa Studies on Potassium Absorption Characteristics of Different Growing Year Alfalfa(Medicago Sativa L.) DIURNAL CHANGES OF PHOTOSYNTHESIS AND TRANSPIRATION OF MANUALLY PLANTING PUCCINELLIA TENUIFLORA