Potential Loss of Nitrogen from a Paddy Rice Field Applied with Liquified Manure.

Main pathway of nutrient transport in agricultural field is leaching and surface runoff by rainfall. The non-point pollutants discharged from rice paddy fields applied with manure liquefied fertilizer (MLF) and commercial chemical fertilizer (CF) was investigated by plot-scale study over rice growing season of year 2004 and 2005 in Korea. The amount of fertilizers to be applied was calculated to furnish 110 kg∙N ha^-1 to each plot. Total 13 runoff events occurred over experimental period; 7 and 6 times for 2004 and 2005, respectively. The ranges of runoff coefficient, the ratio of runoff for rainfall, were 0.19~1.23.
The effluents were collected, whenever runoff occurred, to investigate the discharge amount of organic matter, nitrogen species, and phosphorous species. Due to lower infiltration rate measured (<0.1 mm d^-1), only nutrient loss by infiltration was assumed negligible.  The discharge loads of organic matter (OM), suspended solid (SS), total-N (TN) from MLF plot was always higher than those from CF plot. Total loss of nitrogen mostly was contributed by first runoff event.  The sEMC (single event mean concentration) of TN from both plots were significant different (p<0.05). In MLF plot, organic nitrogen (ON) and nitrate-N were the major forms in nitrogen. On the contrary CF plot, ammonia-N was the major form. Nitrite-N was a lowest portion in both plots. 
The total phosphorus (TP) loss from MLF and CF plot were 12.52 and 12.88 kg ha^-1, respectively. There were not significantly different between two plots (p<0.05). Approximately 49~94% of the discharged form of phosphorus was particulate phosphorus. The percentage of dissolved phosphorus among TP loss was 18% in MLF plot, but it was even less (>10%) in CF plot.