Based on the statistic data of crop yield and farmland produce investment in the period from 1990 to 2009,carbon emission,carbon absorption and carbon footprint of the farmland ecosystems were estimated in China.Conclusions were reached as follows:Carbon emission amount and intensity,carbon absorption amount,and carbon footprint on the increase,carbon absorption intensity was stable,with the large number of agricultural use of fossil energy,carbon footprint per unit area of 0.08 hm2/hm2 rose from 1990 to 20...