engleski

LOSS OF NITROGEN WITH DRAINAGE WATER IN A LONG TERM FIELD EXPERIMENT

In a long term field experiment with different nitrogen rates the effect of nitrogen fertilization upon the concentration of nitrate and ammonia nitrogen in subsurface drainage water was studied in a period from 1997 to 2007. Increased rates of applied nitrogen led to higher average values of NO3--N concentration in drainage water. In treatments of up to 150 kg ha-1 N, average nitrate nitrogen subsurface runoff concentration was lower than 15 mg/L for the investigation period (1997 - 2007). Maximum average concentration increased to 25.8 mg/L NO3--N treated with 300 kg ha-1 N. Average ammonia nitrogen concentration ranged from 0.27 mg/L to 0.37 mg/L during the investigation period and were not in correlation with applied fertilization doses. Losses of nitrate and ammonia nitrogen through drainage water varied from 6.3 kg/ha to 28.4 kg/ha, and from 0.24 kg/ha up to 0.52 kg/ha, respectively, depending on nitrogen rate applied. Results substantiate the importance of investigating the influence of different nitrogen rates applied for fertilization of arable crops upon nitrogen leaching in the agroecological conditions of Croatia, especially in regions where intensive agricultural production is practiced.

Subsurface drainage; Nitrogen; Leaching

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