title: [Fixed ammonium content of chief paddy soil types in Hunan Province and its influencing factors].
abstract: By the method of Silva and Bremner, the fixed ammonium content of chief paddy soil types in Hunan Province and its influencing factors were studied. The results showed that the content of fixed ammonium in plough layer ranged from 141 mg.kg-1 to 353 mg.kg-1, averaged 272 +/- 67 mg.kg-1, and accounted for 11.2% of total soil N. The content of fixed ammonium was in order of alluvial sandy soil > purple clayey soil > newly alluvial sandy soil > yellow clayey soil > reddish yellow clayey soil. There were four distribution models of fixed ammonium in the soil profiles: 1) fixed ammonium content increased with the increase of depth in the profiles; 2) fixed ammonium content decreased with the increase of depth; 3) there was no distinct change; and 4) abrupt increase or decrease was found in the profiles. The percentage of fixed ammonium to total N in soils always increased with the increase of depth. The fixation of NH4+ by soil was the strongest under 30 degrees C. Long-term submergence benefited to the fixation of NH4+ in newly alluvial sandy soil, purple clayey soil, and alluvial sandy soil, while the alternation of drying and wetting contributed to the fixation of NH4+ in yellow clayey soil best. The content of fixed ammonium in tested soil was correlated with the content of clay < 0.01 mm at the significant level, and not correlated with the content of clay < 0.001 mm, total N, organic N, and matter.
authors.affiliation: College of Resource and Environment Science, Hunan Agricultural University, Changsha 410128. Zhangyangzhu@263.net
authors.forename: Yangzhu
authors.initials: Y
authors.lastname: Zhang
authors.forename: Jipei
authors.initials: J
authors.lastname: Liao
authors.forename: Fayun
authors.initials: F
authors.lastname: Li
authors.forename: Yunxiang
authors.initials: Y
authors.lastname: Huang
authors.forename: Ruizhi
authors.initials: R
authors.lastname: Hu
authors.forename: Zhengping
authors.initials: Z
authors.lastname: Yuan
mesh_terms: D012275:Oryza; D000644:Quaternary Ammonium Compounds / Q000032:analysis*; D012987:Soil / Q000032:analysis*; D013696:Temperature
chemical_list: D000644:Quaternary Ammonium Compounds; D012987:Soil