Effect of fertilization on composition and spatial distribution of dissolved organic nitrogen in paddy soil-microbial systems

Abstract

Dissolved organic nitrogen (DON) has high bioavailability and is an important source of soil nutrients. In order to determine the concentrations and the composition of DON in different depths (0-30 cm), and provide a theoretical basis for further deep research into the paddy soil nitrogen supply, experiments based on the lysimeter method were carried out to investigate the effect of fertilization on composition and spatial distribution of DON in paddy soil. Paddy soil was treated under chemical fertilization treatment (CT) and mixed fertilization treatment (MT). With methods of PCR-DGGE and HPLC-MS, the results of the experiments suggested that the samples in 10-20 cm and 20-30 cm under MT had significantly higher bacterial diversity than those under CT except in 0-10 cm. DON had a high percentage (63.1-79.9%) in Ntot of soil solution. The results of the correlation analysis revealed that DON had a significant positive correlation with organic matter content, Shannon-Wiener diversity index (H') and a significant negative correlation with pH. The possible results of HPLC-MS identification of DON from paddy soil solution were that (a) 3-(4-thiazolyl)-l-alanine; (b) 2-phenylbenzimidazole-5-sulfonic acid; (c) 4-(2, 4-difluorophenyl)-3-nitrobenzene carbaldehyde; (d) fendizoic acid.