Agricultural sustainable intensification improved nitrogen use efficiency and maintained high crop yield during 1980-2014 in Northern China

Global population increase will require rapid increase of food production from existing agricultural land by 2050, which will inevitably mean the increase of agricultural productivity. Due to agricultural sustainable intensification since the 1990s, crop production in Huantai County of northern China has risen to 15tha^-1yr^-1 for the annual wheat-maize rotation system. We examined the temporal dynamics of nitrogen (N) budget, N losses, and N use efficiency (NUE) during the 35years (1980-2014) in Huantai. The results revealed that atmospheric N deposition increased 220% while reactive N losses decreased by 21.5% from 1980s to 2010s. During 1980-2002, annual N partial factor productivity (PFP_N), apparent NUE and N recovery efficiency (RE_N) increased from 20.3 to 40.7kggrainkg^-1N_fert, from 36.5% to 71.0%, and from 32.4% to 57.7%, respectively; meanwhile, reactive N losses intensity, land use intensity and N use intensity decreased by 69.8%, 53.4%, 50.0%, respectively, but without further significant changes after 2002. Overall increases in NUE and decreases in N losses were largely due to the introduction of optimized fertilization practice, mechanization and increased incorporation of crop straw in Huantai. Straw incorporation was also significant in soil N stock accrual and fertility improvement. By 2030, northern China may reach the lowest end of PFP_N values in developed countries (>45kggrainkg^-1N_fert). These agricultural sustainable intensification practices will be critical in maintaining high grain yields and associated decreases in environmental pollution, although water use efficiency in the region still needs to be improved.