Simulation of nitrogen leaching and nitrate concentration in a long-term field experiment Simulace vyplavení dusíku a koncentrace nitrátů v dlouhodobém polním pokusu

The effects of organic and mineral nitrogen fertilization on nitrogen leaching and nitrate concentration in percolated water were simulated using the CANDY model. In a long-term IOSDV field experiment carried out from 1983 to the present in Lukavec, Czech Republic, increasing nitrogen rates from 0 kg to 200 kg N*ha in mineral fertilizers were combined with the application of farmyard manure or straw, the control treatment was without organic fertilization. The simulation results of four rotations in the years 1996 – 2007 are presented. In the treatments, the average simulated nitrogen leaching ranged from 2 kg to 71 kg N*ha y, the average nitrate concentrations were between 5 mg and 191 mg*l. The average year concentration of nitrate about 40 mg*l indicated increasing occurrence of concentrations above 50 mg*l at daily basis. Nitrogen leaching and nitrate concentrations were non-linearly related to the total nitrogen inputs (R= 0.98), the organic fertilizer treatments only negligibly altered the form of the relationship. The average nitrate concentration exceeded 50 mg*l at a total nitrogen input level about 150 kg N*ha; this corresponding to an average leaching of 20 kg N*ha y.