Research on Chinese future grain security based on the method of EMD.

【Objective】 Grain security problem is the first importance for our government to solve.The rapid increase of future population and food consumption coupled with a decrease of total cultivated land at a rather greater speed in recent years will badly affect the safety of grain security in our country.【Method】 In this paper,Empirical Mode Decomposition(EMD) method was introduced to study the fluctuation of grain output and cultivated land and their causes at multi-time scale from 1949 to 2006,then a dynamical model is established to predict the grain tendency production and cultivated land change in the next 30 years,through which the future grain security based on population development and cultivated land change was analyzed.【Result】 The results of study are as follows:(1) The fluctuations of grain output have 3.6-year,9.6-year and 14.5-year time scales and fluctuation of the 9.6-year time scale is more prominent.Cultivated land mainly has a 14.5-year time scale.(2) Shown from the residual trend term of grain output,till the people-estimated peak of population of 2030,the grain output can satisfy the requirement of 1.49 billion people at a per capita consumption of 400-470 kg grain.However,grain output of 1010 kg every ten years should be increased and a great effort should be made and to expand the potentials of grain production,which will be disadvantageous to the sustainable development of future agriculture.(3) Shown from the residual trend term of cultivated land,when the productivity per hectare increased to 5008-5133,5598-5798 and 6439-6725 kg in 2010,2020 and 2030,and the same proportion of grain planting is always kept,the grain production based on cultivated land can absolutely ensure 95% self-sufficiency goal brought forward by the white book 《Food Issue in China》.However,further increase in per capita grain occupancy is not optimistic,due to the restriction of limited arable cultivated land resources.【Conclusion】 The foreground of future grain security in our country is not optimistic.Fromthe correlation between population,farmland and grain output,we must strictly control the population growth,increase the quality and utilization rate of total farmland and encourage scientific technology to improve the cultivated land productivity.