The Earth Summit held in Rio-de-Janerio in June 1992 and Kyoto Conference on Climate Change in Dec.1997 made it mandatory for all countries to establish Greenhouse Gas Emission Budget and to develop mitigation strategies. Among these gases nitrous oxide (N2O) is a globally important and relatively long lived trace gas (Atomspheric lifetime 150 yrs., Present atmospheric concentration 315 PPbv) with potent greenhouse properties and a natural species act as reactant in destruction of stratospheric ozone layer. N2O have a biogenic source and sink and exchange between soil and atmosphere is an important contributary factor to global climate change phenomenon.

Dry tropical soils are an important natural source of N2O and contribution from different ecosystem habitats are of the much ecological significance in increasing the N2O pool in the atmosphere. In the present study N2O fluxes were measured monthly for two years from Teak (Tectona grandis L.) dominated climax dry deciduous forest, moderately grazed grassland, eutrophicated shallow water body and leguminous (Soybean / Chickpea sown) Agroecosystem (located between 22°43’N – 23°11’N latitude and 75°43’E – 75°48’E longitude) at field condition by using closed chamber technique. Different soil parameters like mineral nitrogen status (NH4-N, NO3-N), total nitrogen, organic carbon, soil temperature, soil moisture were measured. Beside these factors nitrification and mineralization capacity of soil, responsible for controlling the N2O fluxes were also measured in soil samples obtained concomittantly while N2O flux measurement were made.

Annual mean of N2O emission indicates that grassland occupying seral ecological status emitting higher N2O (3.69 kg ha^-1 y^-1) as compared to other habitats such as managed leguminous agroecosystem (3.13 kg ha^-1 y^-1), climax forest soil (2.66 kg ha^-1 y^-1) and the wetland ecosystem (1.0 kg ha^-1 y^-1). Fluxes showed considerable variation during different seasons and highest emission of N2O were recorded during rainy season in studied terrestrial habitats, while in wetland ecosystem highest flux were recorded during summer season. Emissions were significantly correlated with soil moisture, soil temperature and NO3-N in dry deciduous forest. In grassland soil N2O fluxes were correlated with NO3-N and NH4-N, while in agriculture field significant correlation observed with soil moisture only. In forest ecosystem, during summer season, when soil temperature ranged to high from 38 to 40°C and correspondingly stressed to soil moisture 5-17%; significant negative fluxes (soil uptake) of N2O, 710 micro g m^-2 d^-1 were recorded. This observation that atmospheric N2O is consumed / decomposed in relatively dry and oxic soil is curious and of ecological significance in dry tropical habitats. N2O sink is an unusual trend unlike most of the reported in literature, need to establish mechanisms involve behind this sink phenomenon which is still unknown.
Overall results of present study provides intriguiting information about source-sink potential with seasonal variability and gradient of factors that controls both fluxes and ecosystems properties and processes. Data of N2O fluxes from different dry tropical ecosystems from Indian subcontinent are very rare and useful for extrapolating the fluxes and for calculating budgets of nitrous oxide for the national N2O campaign and for the national communication to the United Nations Framework for Climate Convention (UNFCC).