Variation of soil quality in typical farmlands in China under long-term fertilization and research expedition

【Objectives】 Fertilization, as the major practice in increasing crop yield, significantly affects soil quality. Researches on the relationship between long-term fertilization and soil quality have been hot spots. During the last three decades, the input in agriculture has been increased and the grain yields have achieved eleven continuous growths since 90s in last century in China, which has definitely produced great influence on soil quality. Investigation on the variation of soil quality after a long term different fertilization modes is critical to keep the sustainability of soil quality and maintain stable grain yield in China. 【Methods】 Papers related to soil quality in farmland under long-term fertilization around China were reviewed in this paper. The effects of long-term fertilization on the main physical and chemical properties were summarized, the research focuses, present situation were discussed and expedition in the future was proposed.【Results】 1) Thirty one papers were collected in this issue, and over 60% of them focused on the study of soil organic matter and phosphorus availability, indicating the soil organic matter and phosphorus balance are the two key indexes in the evaluation of soil quality in farmland in China. 2) After nearly 30-years?? continuous application of chemical fertilizers, the soil organic matter content (SOM) in the black soil in northeast China is decreased at rate of 1 g/kg per decade, but increased at a rate of 1.4-2.5 g/kg per decade in other areas. Long-term combined application of organic manure and straw with chemical fertilizers benefits the accumulation of SOM, the increase rated is respectively 51% and 68% in the northwestern and the north China, and 24% in dry land of the southern China and paddy field in the Yangtze River catchments. 3) The average carbon efficiency of organic materials is 16.3% in cropland in China, which is decreasing with the increasing gradients of precipitation and temperature. The average efficiency of carbon utilization in northwestern and northeastern China is 22%-26%, greater than those in northern (13%) and southern part of China (10%). 4) Fertilization managements have significantly influenced soil available phosphorus (P) contents. When the annual P application rate is 20-33 kg/hm2, the contents of total P and available P in soil keep stable on a certain level or greatly increased depending on both the soil type and P application rate, with the highest increase of 2.1 mg/kg annually. 5) Combined application of organic manure and chemical fertilizers will significantly activate stored P in soil, and expending the room for available P increase. The maximum increase in available P content could be as high as 9.3 mg/kg. 6) Fertilizer P application could promote the accumulation of soil P in the form of active inorganic P (Ca2-P, Ca8-P, Al-P, Fe-P), while the combined application of fertilizer P with organic manure will greatly increase the content of active organic P pool in soil.【Prospects】Under present intensive agricultural management in China, the primary factor affecting the balance of soil organic matter is sufficient application of organic materials. More researches on soil quality should be focused on soil biological index, soil ecological and healthy function, and the evolution of soil quality. Meanwhile, more attention should be paid on the development of proper models and the optimization on the best-fitted parameters, to enhance the simulation and forecast of the change trends of soil quality in agro-productive practices in the future.