China has been increasing grain production since 2004 by using more chemical fertilizers. A study compared fertilizer use in wheat, rice, and maize crops in 2001 and 2008. They found that fertilizer application rates increased for wheat and maize, but decreased for rice. Despite total fertilizer consumption going up, the proportion used on grain crops decreased. The efficiency of fertilizer use, measured as PFP, was highest for rice, followed by wheat and then maize. Over the years, PFP increased for wheat and rice, but decreased for maize. Changes in crop planting affected fertilizer efficiency, with more cereal crops improving efficiency, but more economic crops decreasing it in China.