NITROGEN DYNAMICS AS INFLUENCED BY VARIOUS LAND USE SYSTEMS OF A MICRO-WATERSHED IN NORTHERN TRANSITION ZONE OF KARNATAKASabyasachi Majumdar and P. L. PatilAbstract An investigation was undertaken during 2013-14 in northern transition zone of Karnataka to study the forms and distribution of nitrogen under different land use systems in Singhanhalli-Bogur micro-watershed. Three land use systems [agriculture (paddy land and non paddy land), forest and horticulture] were selected for the study. From each land use system, fifteen surface (0-20 cm) soil samples were collected randomly and analyzed for forms of nitrogen. The exchangeable ammonical nitrogen values of surface soil samples varied between 8.4 to 36.4, 14.0 to 47.6 and 16.8 to 35.6 mg kg-1 under agriculture, horticulture and forest land use systems, respectively. Nitrate nitrogen values of surface samples ranged between 2.8 to 47.6, 3.9 to 25.2 and 8.4 to 24.7 mg kg-1 under agriculture, horticulture and forest land use systems, respectively. Total nitrogen content decreased with depth in almost all the profiles and ranged from 270 to 1000 mg kg- 1. There was a significant positive correlation recorded between total nitrogen and clay content under all the land uses systems except non-paddy land. The contribution of inorganic nitrogen fractions to total nitrogen was very low.
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