CHED 855 |
| A. C. Evans, J. S. McConnell, P. B. Francis, C. R. Stark, and C. K. Bryant. |
| Nitrogen (N) fertilizer use in cotton (Gossypium hirsutum L.) production has come under scrutiny as a potential source of nitrate (NO3-) contamination of streams and ground water. This study was conducted to determine the distribution of NO3--N in soil cropped to continuous cotton, and to evaluate fertilization practices and irrigation methods that might exacerbate the accumulation of NO3--N in the soil profile. Long-term studies of N-fertilization and irrigation methods at the Southeast Branch Experiment Station near Rohwer, Arkansas, on an Hebert silt loam (fine-silty, mixed, thermic Aeric Ochraqualfs) soil were utilized. Nitrogen fertilizer treatments ranged from 0- to 168 kg N ha-1, and were applied from 1982 through 1999. Nitrogen treatments were discontinued from 2000 through 2003, then resumed in 2004. The irrigation blocks were center pivot irrigated, furrow flow irrigated, and dry land. Soil samples were taken in the spring (1994, 2000, 2004) prior to N-fertilization to a depth of 1.5 m in 15-cm increments from each N-treatment within each irrigation block and analyzed for NO3--N. Soil cropped to dry land cotton showed excessive accumulation (up to 101.2 mg NO3--N kg-1) of NO3--N when treated with N-rates of 67 kg N ha-1 and greater. Soil cropped to irrigated cotton did not accumulate as much NO3--N as dry land. Soil NO3--N was unaffected by N-treatment under center pivot irrigation. Slight increases in soil NO3--N were observed under furrow-irrigation with the greatest N-treatments (134 and 168 kg N ha-1). After four years of discontinued N-fertilizer treatments, residual soil NO3--N was depleted under furrow and center-pivot irrigation. Residual NO3--N under dry land production conditions was substantially less in 2004 than either 1994 or 2000. Plant uptake and utilization of residual soil NO3--N is thought to be the primary mechanism for depletion of soil NO3--N in this study. |
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Undergraduate Research Poster Session: Environmental Chemistry
2:00 PM-4:00 PM, Monday, 27 March 2006 Georgia World Congress Center -- Ex. Hall B4, Poster
Division of Chemical Education |