engleski

Leached Phosphorus Measured in Drainage Water through a Field Experiment with Varying Nitrogen Rates

According to many studies done worldwide, critical levels of phosphorus in water above which eutrophication is likely to be triggered are approximately 0.03 mg/L of dissolved phosphorus and 0.10 mg/L of total phosphorus. Phosphorous dissolved in surface runoff water and lost from the soil system can range from 0.01 kg/ha up to 3.00 kg/ha annually, depending on the land use. Annual leaching losses of P to groundwater can be from 0.0001 up to 0.40 kg/ha. The latter is the highest value measured in an agroecosystem. The effect of NPK fertilization upon the concentration of phosphate in subsurface drainage water was studied in a field experiment with different nitrogen rates (from 0 up to 300 kg/ha) and constant P (120 kg/ha) and K (180 kg/ha) rates. Increased rates of applied nitrogen led to lower average values of P-PO43- concentration in drainage water. Average P-PO43- concentration noted in the investigation period (1997 - 2010) was in a range from 0.09 mg/L P-PO43- in the treatment with 250 kg ha-1 N up to 0.21 mg/L P-PO43- in the treatment with no nitrogen applied but applied with P and K. Average values of P-P2O5 losses, over a fourteen year investigation period, through drainage water, varied from 0.08 kg/ha to 0.22 kg/ha depending on nitrogen rate applied. Values were in complete negative correlation (r=0.9121) with applied N fertilization doses. These results substantiate the importance of investigating the influence of different N rates and constant P and K rates upon inorganic element leaching in the agroecological conditions of Croatia, on Stagnosol, notably in regions where intensive agricultural production is practiced.

Subsurface water; Drainage; Phosphate; Leaching; Fertilization; P loss

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