Nitrate Movement Through the Soil Profile in Relation to Tillage System and Fertilizer Application Method

AN experiment was performed to determine the movement of NOa-N through no-till and moldboard-plowed field plots. On the plowed plots, NOa-N (about 150 kg/ha) was surface broadcasted either before or after tillage; on the no-till plots, only surface application of NO3-N without tillage was used. Two rains of 12.7 and 6.35 cm (2.3 cm/h) were applied about one day apart with a rainfall simulator to the 5x5 m plots. Soil sampling down to 150 cm was performed before and after rainfall for soil water content and N03-N analyses. Results showed that plots under no-till maintained significantly higher N03-N amounts in the 0- to 30-cm layer, with 40% of the N03-N initially present still there after 12.7 cm of rain and 33% remaining after the additional 6.35 cm of rain. The corresponding numbers for the moldboard-plow plots were 19 and 9%. The amount of N03-N leached from the 150-cm profile with 12.7 cm of rain was also less (29 kg/ha) for the no-till compared with moldboard-plowed plots (122 kg/ha).