| Using the observed data of spring-sowed two years fresh alfalfa growth condition and parallel climatic conditions,analysis is made of the alfalfa's growth height and the speed variation rule with time in the loess plateau area of East Gansu,and the correlation dependence of dry matter and the fresh grass with the activity accumulated temperature.The model is revised according to the forage grass climate productivity photosynthesis output and the temperature and the precipitation,and the climate productivity of alfalfa is computed.The results show that,when sowed in spring,the growth height increase quantity reaches the top in blossoming～withering and turning yellow period in the same year and flower bud appearing～florescence in the second year,while the fastest growth speed occurs in germinating～branching and flower bud appearing～florescence periods.The dry matter weight and fresh grass weight and the activity accumulated temperature reach the maximum simultaneously in branching～flower bud appearing period.The moisture content is the main limiting factor of the alfalfa climate productivity potential in East Gansu.At present there is still a great deal of climate productivity potential in the center north loess knoll gully area for further use. |