the effect of temperature and carbon dioxide on dissolved nitrogen forms in a calcareous soil

elevated atmospheric carbon dioxide and other green house gases have increased the earth temperature in recent century, which it affects all biochemistry cycles in soils. to examine the effect of atmospheric co2 concentration and temperature on n forms in soil solution in a calcareous soil, an experiment was conducted in a completely randomized design with factorial arrangement in the laboratory conditions. initially, soil was treated with one percentage of cattle manure compost and 200 kg ha-1 of urea, then changes in forms of soil nitrogen (total dissolved nitrogen, dissolved inorganic nitrogen, dissolved organic nitrogen, sum of nitrate and nitrite and ammonium) were evaluated in two levels of temperature (25 and 35 oc) and two different carbon dioxide concentrations (350 and 700 ppm) during 60 days of incubation with three replications. the results showed that the effect of carbon dioxide on nitrogen forms was different at 25 and 35 oc. carbon dioxide increased dissolved organic nitrogen but dissolved inorganic nitrogen and nitrate and nitrite decreased at 25oc treatment. while total dissolved nitrogen, dissolved inorganic nitrogen and no2 + no3 increased at 750 ppm of carbon dioxide treatment, it had no effect on dissolved organic nitrogen. changes in dissolved organic nitrogen were higher than other forms of nitrogen during the experiment. the maximum and minimum dissolved organic nitrogen were occurred faster than other nitrogen forms at 35 oc treatment. the results of this experiment showed that elevated carbon dioxide with increasing temperature increased the rate of nitrogen biochemical reactions in soil.