• journal_title：Vadose Zone Journal
• Contributor：Nathan E. Derby ; Francis X. M. Casey ; Raymond E. Knighton
• Publisher：Soil Science Society of America
• Date：2009-
• Format：text/html
• Language：en
• Identifier：10.2136/vzj2007.0162
• journal_abbrev：Vadose Zone Journal
• issn：1539-1663
• volume：8
• issue：2
• firstpage：290
• section：ORIGINAL RESEARCH

Proper N management for agricultural production is critical to minimize groundwater contamination with NO₃. For 18 yr, research was conducted to observe NO₃–N concentrations in the vadose zone, groundwater, and subsurface drainage under sprinkler-irrigated, primarily corn (<em>Zea maysem> L.) production. Potato (<em>Solanum tuberosumem> L.) and soybean [<em>Glycine maxem> (L.) Merr.] were also grown intermittently on the site. The lysimeter leachate NO₃–N concentration increased to 156 mg L⁻¹ under corn production within 1 yr after the initiation of irrigation (at the onset of the study), then decreased to <10 mg L⁻¹ during a 6-yr period of best-management N fertility management for corn. The average yearly lysimeter NO₃–N concentration fluctuated between 8 and 117 mg L⁻¹ during the study. Nitrate concentrations in the shallow groundwater followed a similar time series trend as leachate concentrations, but with lower concentrations and lagging about 1 yr. Subsurface drainage NO₃–N concentrations were much lower but followed the same trend as the shallow groundwater. An N balance indicated higher net N mineralization after the initiation of irrigation and the years after potato production. Fertilizer N application rates and yearly weather conditions, which affected crop vigor and N uptake, combined to affect the fall residual soil NO₃. Fall soil NO₃ from 0- to 1.8-m depth was the most significant factor influencing the leachate NO₃–N concentration each year during the study (<em>rem>² = 0.76).