[China's crop residues resources evaluation].

The availability of crop residues in China is reviewed in this article. The definition of crop residues is clarified as the total byproducts of field production and processing industry thereafter, and methodology for evaluating crop residues is discussed. Based on literature, the progress on the crop residue assessment is addressed. The annual field crops residues in China from 1991 to 1999 were estimated between 6.0-6.8 hundred million tons, while the data for the process residues were not available. From 2000 to 2007, the annual crop residues were estimated between 5.9-7.3 hundred million tons, while the processing residues at the range of 0.9-1.1 hundred million tons. The reasons for the significant variations are due to the disagreement on crop residue definition, different, even inaccurate residue to grain ratio data used in the estimations, and the lacking of clear understanding on the statistical analysis and grain outputs related to the crop residue evaluation. With the complete statistic analysis method, the author's group evaluated the residues in 2006 and 2007 to be 7.4 hundred million tones in total, including 6.5 hundred million tons for field crop residues and 0.9 hundred million tons for process residues. Moreover, the geographic distribution of the field crop residues was analyzed based on the harvest indices (HI) tested within the near five years.