Effect of different land use systems on the form and distribution of organic nitrogen in brown soil

Influence of different land use systems(naturally needle broad-leaved secondary forest,tussah woodland,and tilth land) on organic nitrogen form and distribution in brown soil were studied under field condition.Soil samples(020,2040,and 4060 cm) were collected from each of land use system.Results showed that the influence of different land use systems on the organic nitrogen forms was the strongest on 020 cm soil layer.The content of all the organic nitrogen forms in naturally needle broad-leaved secondary forest land was the highest,followed by tussah woodland and tilth land.Contents of all forms of organic nitrogen decreased significantly with increasing of the depth for naturally needle broad-leaved secondary forest land and tussah woodland,but the distribution of different forms of organic nitrogen under tilth land use system showed a big variation.The result also indicated the proportion of organic nitrogen forms was ammo acid-Nhydrolysable unknown-Nammonia-Nammonia sugar-N under second forest land and tussah woodland land use systems,but land use of tilth was different which was hydrolysable unknown-Nammo acid-Nammonia-Nammonia sugarN.The proportion of ammonia-N under tilth land was larger than second forest land and tussah woodland at 040 cm soil layer.