Submitted to: American Society of Agricultural Engineers Meetings Papers
Publication Type: Other
Publication Acceptance Date: July 22, 1999
Publication Date: N/A
Technical Abstract: The effects of crop management systems including tillage, rate of fertilizer application, and type of application on the transport of nitrates in surface runoff were studied on two field-size watersheds, Farming System 1 (FS1) and Farming System 2 (FS2) located in the claypan soil region of north-central Missouri. Water samples were collected from the drainage areas for NO3-N and NH4-N analysis during each runoff event from 1993-1997. On an average, nitrate loss to surface runoff from the fields accounted for 6.0% of the total fertilizer N applied to the soil with more than 75% of the total loss occurring within 6 weeks following application. In some years, a single event accounted for almost 50% of the annual nitrate loss to surface runoff. In 1993, fertilizer applied on FS1 was 2.3 times higher than FS2; however, annual nitrate loss to runoff from FS1 was only 21% higher than FS2 and was mainly attributed to difference in nrunoff volume. In 1995, nitrate loss to surface runoff from FS1 where fertilizer was surface applied and incorporated was 13% less than FS2 where fertilizer was surface applied and not incorporated, although fertilizer applied on FS1 was 22% higher than FS2. In 1997, nitrate loss to surface runoff from minimum till (FS1) where fertilizer was surface applied and incorporated was 3 times higher than that from no-till (FS2) where fertilizer was knifed-in. In general, the study showed that the method of incorporation, runoff volume, and timing of a runoff event relative to the date of application had a the greater influence on nitrate loss to surface runoff than did the application rate.