Change characteristic of nitrogen recovery efficiency of wheat in typical farmland of China under long-term fertilization

The change characteristics of nitrogen recovery efficiency (NRE) of wheat on 9 typical farmlands in China were analyzed based on the results of 15 to 24 years long-term fertilization experiments. The results showed that NRE of wheat in black soil and grey desert soil didn’t changed markedly with time under neither single application of nitrogen (N) nor combine application of N and K (NK), but it was decreased in other soils under same treatments with the order of decreasing rate: red soil (7.24) yellow brown soil (4.16) cumuli cinnamon soil (1.48), neutral purple soil (1.44), fluvo-aquic soil (1.06) lime purple soil (0.60). Additionally, NRE of wheat with combined application of chemical fertilizers (NP and NPK) and manure (NPKM) was rather consistent with time in fluvo-aquic soil，gray desert soil，yellow brown soil，black soil and neutral purple soil. NRE under the treatment of balanced chemical fertilizers (NPK) in cumuli cinnamon soil, fluvo-aquic soil, cinnamon soil, gray desert soil, yellow brown soil, black soil, neutral purple soil, and red soil was 76.8%，73.4%，56.4 %，44.9%，44.4%，33.8%，41.7%，33.6% respectively, indicating that NRE was different among the soils. NRE of soils collected from warm temperate zone of Northern China (cumuli cinnamon soil，fluvo-aquic soil, cinnamon soil and gray desert soil) were higher than the soils from the subtropical area of South China (yellow brown soil，purple soil and red soil ) and black soil in mid-temperate zone. The spatial variability of NRE had significant correlation with contents of soil organic matter, soil pH, and geographic latitude, especially for the soils from northern China.