Fig. 2.

Changes in agricultural managements and crop residue C inputs since 1980. (A) Changes in grain yield, chemical fertilizer consumption, and the rate of straw/stover return to soils in China since 1978. Grain production and chemical fertilizer data were sourced from National Bureau of Statistics of China (data.stats.gov.cn), and rates of crop straw/stover return were based on 4,060 sites in the 58 counties sampled in this study. (B) Changes in average C inputs across the 4,060 sites in the 58 counties investigated. C inputs through straw/stover incorporation were estimated using crop yield data recorded by county-level agricultural census, straw/stover return rate derived from 4,060 sites in the 58 counties, and the grain:straw ratios of 333 sampled plots across the 58 counties. C inputs by roots were estimated using the crop yield data reordered by county-level agricultural census and the root:grain ratios of 333 sampled plots across the 58 counties.