Black soil has high natural fertility with organic C of 28 g kg−1 in the control treatment. After 13
years crop production, the organic C decreased by 10% as compared to the initial value (Table I). This
is a relatively short time span. Yu et al. (2004) studied the organic C changes of the cultivated black
soils for the period of the past two hundred years and found that the organic C tended to decrease with
increasing tillage years. However, after 130 years of tillage, the soil organic C remained at a relatively