NITRATE LEACHING LOSSES FROM MONOLITH LYSIMETERS AS INFLUENCED BY NITRAPYRIN

Three monolith lysimers, each with a surface area of 8.1 m2 and a depth of 2.4 m, were planted to no-till corn (Zea mays L.) for 6 consecutive years. The lysimeters contained a Rayne silt loam (Typic Hapludult), a well-drained residual soil. Urea was placed in a slot approximately 10-cm deep and 10 to 15 cm from the corn row at a rate of 336 kg N/ha. The urea applied to two of the lysimeters was treated with nitrapyrin [2-chloro-6-(trichloromethyl)pyridine], a nitrification inhibitor, and applied untreated on the third lysimeter. Two yearsof unfertilized meadow immediately preceded the corn. Concentrations of .**GRAPHIC**. in the leachate from the lysimeters were higher during the corn years than during the meadow period. Concentrations showed seasonal variations during the last 3 yr of the study, but showed no increasing trend. The leachate from the lysimeters receiving the nitrapyrin treated urea had seasonally flow-weighted .**GRAPHIC**. concentrations ranging from 6 to 40 mg/L, while the leachate from the lysimeter receiving untreated urea had seasonally flow-weighed .**GRAPHIC**. concentrations ranging from 20 to 54 mg/L. Nitrate-N losses showed a similar treatment difference. The 6-yr annual average .**GRAPHIC**. loss was 117 and 160 kg/ha from the lysimeters with the treated urea and untreated urea, respectively. This study demonstrates that nitrification inhibitors such as nitrapyrin, have a potential to reduce .**GRAPHIC**. leaching when applied with ammoniacal fertilizers.