The study looked at changes in soil properties and fertility in a large grain-producing area in China over a 10-year period. They collected soil samples in 2007 and 2017 and measured pH, organic matter, nitrogen, phosphorus, and potassium levels. They found that soil fertility declined overall, with organic matter and potassium decreasing significantly. Different crop rotation systems had varying effects on soil fertility, with double rotation systems showing higher fertility levels. The study also identified changes in soil properties due to factors like cropping systems, fertilization practices, and reduced acid rain.