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Title: Nitrate Loss in Subsurface Drainage from Mid-Season N Fertilizer Application

item Jaynes, Dan
item Colvin, Thomas

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 11/10/2005
Publication Date: 11/10/2005
Citation: Jaynes, D.B., Colvin, T.S. 2005. Nitrate Loss in Subsurface Drainage from Mid-Season N Fertilizer Application [CD-ROM]. In: ASA-CSSA-SSSA Annual Meeting Abstracts, Nov. 6-10, 2005, Salt Lake City, UT.

Interpretive Summary:

Technical Abstract: To better tailor nitrogen (N) fertilizer application to crop need, there is growing interest in applying N to corn at mid-season. While the yield benefits of this practice are mixed, little information is available as to the impacts of mid-season N application on water quality. We compared grain yields and nitrate losses in drainage water as a result of applying N either once at emergence or equally split between emergence and mid-season. Nitrogen treatments consisted of 138, and 69 kg ha-**1 applied at emergence and 69 kg ha-**1 applied at emergence and again at mid-season. Grain yield for corn and soybean, grown in a two-year rotation, and drainage water nitrate were measured on replicated tile-drained plots within a producer's field from 2000 through 2003. Corn grain yields for the mid-season treatment (10.27 Mg ha-**1) was significantly greater than the other treatments (9.56 – 9.56 Mg ha-**1) in 2000. In 2002, the mid-season N application increased yield compared to the single 69 kg ha-**1 treatment (11.62 compared to 10.70 Mg ha-**1) but was less than the yield when 138 kg ha-**1 was applied all at emergence (12.42 Mg ha-**1). There was no carry over treatment effect on soybean yields. Nitrate concentrations in tile drainage were consistently greater for the mid-season treatment than the equivalent rate applied all at emergence, but the differences were not significant. Residual soil nitrate at the end of the year also indicated that some of the mid-season N application was not taken up by the plant and was available for leaching. While mid-season N application may be beneficial for recovering some yield potential in corn, the practice does not appear to benefit water quality when compared to a single application at emergence.