Abstract
The impact of chemical to organic fertilizer substitution on soil labile organic and stabilized N pools under intensive farming systems is unclear. Therefore, we analyzed the distribution of soil total N (STN), particulate organic N (PON), microbial biomass N (MBN), dissolved organic N (DON), and mineral N (NO(3)(-) and NH(4)(+)) levels down to 100 cm profile under wheat-maize rotation system in northern China. The experiment was established with four 270 kg ha(-1) N equivalent fertilizer treatments: Organic manure (OM); Organic manure with nitrogen fertilizer (OM + NF); Nitrogen fertilizer (NF); and Control (CK). Results found that the OM and OM + NF treatments had significantly higher STN, PON, MBN, DON, and NO(3)(-) contents in 0-20 cm topsoil depths. Conversely, the NF treatment resulted in the highest (p < 0.01) DON and NO(3)(-) depositions in 40-100 cm subsoil depths. The NH(4)(+) contents in selected profile depths were significantly highest (p < 0.01) under OM treatment. The correlations between STN and its fractions were positively significant at 0-10 and 10-20 cm topsoil depths. Our results suggest that partial substitution of chemical fertilizer with organic manure could be a sustainable option for soil N management of intensive farming systems.