Trends in the soil chemistry of north China since the 1930s

Beliefs about widespread soil degradation can and should be tested against a quantitative history of soil quality over large agricultural regions. Fortunately, Chinese soil-profile data from the 1930s through the 1980s now permit preliminary statistical tests of broad hypotheses about degradation trends for soils of given site characteristics. There is no sign of any trend toward alkalinization in north China. A half-century of experience does confirm that organic matter and N, though not P or K, have declined over broad areas of the North since the 1950s. The patterns of nutrient loss raise new questions about erosion trends, however. The results suggest a broad-based mt uptake of soil nutrients on tilled lands after the 1950s, one that was as rapid in the Huang-Huai-Hai plain as in the famous degradation-prone areas to the west and north. A rise in China's nonagricultural population and land use has not been a clear net drain on the total nutrient reserve of agricultural soils, as many have suspected: it is a very slight net drain on P and K, but a net contribution to the total endowment of organic matter and N on arable lands.