Change in farmland soil fertility and nutrient management strategy in the piedmont of Mount Taihang, North China Plain

The trend, degree and mechanism of change in soil nutrient/fertility in farmlands of Luancheng, Hebei Province was analyzed using soil survey data for 2008, 2000 and 1979, from which a sustainable strategy for agricultural nutrient resource management was put forward. The results indicated a significant change in soil fertility for 1979 through 2008. There was a significant increase (P<0.01) in soil organic matter, Olsen-P, available K, and especially in available N. Average available N increased from 56.7 mg·kg^-1 in 1979 to 80.0 mg·kg^-1 in 2000, and to 109.1 mg·kg^-1 in 2008. This represented an annual increment of 1.1 mg·kg^-1 and 3.6 mg·kg^-1 in 1979~2000 and 2000~2008, respectively. Available N increased by 1.9% and 4.5% annually for 1979~2000 and 2000~2008 and with a total corresponding increase of 41.1% and 36.4%, respectively. The rate of increase in 2000~2008 was higher than in 1979~2000. Soil organic matter content increased from 11.6 g·kg^-1 in 1979 to 11.6 g·kg^-1 in 2008, which represented an annual increment of 0.24 g·kg^-1. Soil organic matter increased by 2.1% annually and by 62.1% in total for 1979~2008. Soil Olsen-P content increased from 17.5 mg·kg^-1 to 24.7 mg·kg^-1 in the 30-year period, represented a total increase of 41.1%. It was then evident that no shortage existed in soil potassium due to the calcareous nature of soils in North China coupled with occasional potassium fertilizer application in the past century. This resulted in a decrease in available K from 140.6 mg·kg^-1 to 111.4 mg·kg^-1 in 1979~2000, representing 20.8% decrease over the period. Available K increased to 149.5 mg·kg^-1 in 2008 as a result of incorporating straw into the soil and increasing potassium fertilizer application in the current century. Soil fertility in the farmlands of Luancheng was high with a high potential for agricultural production. While the key to nutrient management in the region lied with nitrogen, the overall objective of nutrient management was sustainable high crop yield and sound environment. While nitrogen management should include real-time soil nutrient deficiency diagnosis and dosage, phosphorus and potassium management should based on constant soil nutrient monitoring and conservative phosphorus/potassium application. Fertilizer management practices that incorporate straw into the soil and combine the application of organic and inorganic fertilizers should be implemented in the study area.