Time Serial Change of Grain Yield per Hectare and Its Impact Factors in Northeast China

Northeast China is a commodity grain base with strategic role in China,so researches on the change of grain yield per hectare in northeast China is of significance for ensuring China's grain security.Using data from 1978 to 2004,the paper presents a comprehensive analysis on the time serial change of grain yield per hectare in northeast China from 4 viewpoints of period,trend,steady and crops respectively,and illustrates the different impact factors of agricultural production conditions on grain yield per hectare change at different stage using grey relation analysis.