EFFECT OF N FERTILIZER FORMS AND SOIL MOISTURE LEVELS ON THE N GASEOUS LOSSES

In a pot experiment using brown forest soil with clay eluviation (40 kg soil/pot) from Keszthely the gaseous losses of nitrogen (total N, N-2, N2O NO NO2) caused by denitrification were tested. Gas-collecting traps were placed at a depth of 20 cm in the soil. At the same fertilizer N input (6250mgN/pot, 150mg N/kg soil), the effects of two fertilizer forms (KNO3, NH4Cl) and two soil moisture levels (field water holding capacity, WHC= 65% and 100%) were evaluated to the gaseous losses of nitrogen with and without sowing of maize hybrids (two Stira and two Mv 355/pot) as test plants. The composition of the N-containing gases was determined by gas chromatography. From the soil-atmosphere the gas samples were taken 8 times, the sampling times were on the 2, 16, 30, 54, 68, 82, 110, 138-th days of the experiment. Statistical evaluation of the results was performed by analysis of variance. The N gaseous loss in the planted pots was the 12% of the applied fertilizer dose, while in unplanted pots it was nearly the double of it (22%) Consequently, there was a 50% decrease in the denitrification gaseous losses of fertilizer N due to plant N uptake. The N-gaseous loss was significantly higher in cases of KNO3 applications and at the WHC= 100% soil moisture than in NH4Cl treatments and at the WHC= 65%, probably due to more intensive denitrification. In the unplanted pots the amount of N-2 and N2O increased the most (by 95% and by 70%) compared with planted pots. It can be concluded that the improperly applied fertilizer causes significant GHG emissions in the absence of plants.