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Title: NITROGEN REMOVAL IN ORCHARDGRASS AND SMOOTH BROMEGRASS AND RESIDUAL SOIL NITRATE

Author
item Singer, Jeremy
item MOORE, K - IOWA STATE UNIVERSITY

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/9/2003
Publication Date: 5/21/2003
Citation: SINGER, J.W., MOORE, K.J. NITROGEN REMOVAL IN ORCHARDGRASS AND SMOOTH BROMEGRASS AND RESIDUAL SOIL NITRATE. CROP SCIENCE. 2003. V. 43. P. 1420-1426.

Interpretive Summary: Nitrogen uptake in cool-season grasses may aid in capturing excess nitrogen from animal confinement operations or phytoremediation. Limited information exists on the nitrogen dynamics of these grasses at very high nitrogen rates. The objectives of this study were to evaluate nitrogen uptake, recovery, and residual soil nitrate in orchardgrass and smooth bromegrass at optimum and very high nitrogen rates. Nitrogen uptake varied by year because of contrasting environmental conditions. Orchardgrass consistently captured more nitrogen than smooth bromegrass and demonstrated superior potential for uptake at nitrogen inputs up to 672 kg/ha/year. Residual soil nitrate did not accumulate at the low nitrogen rate to levels above 10 mg/kg in the soil to a depth of 0.6 m at a fall sampling. This study confirms that producers who use orchardgrass can capture greater quantities of soil nitrogen.

Technical Abstract: Nitrogen (N) uptake in cool-season grasses may aid in capturing excess N from animal confinement operations or phytoremediation. Limited information exists on the N dynamics of these grasses near the asymptote of the N response curve. The objectives of this study were to evaluate N uptake, recovery, and residual soil NO3-N in orchardgrass (Dactylis glomerata L.) and smooth bromegrass (Bromus inermis Leyss.) at optimum and very high N rates. Nitrogen rates of 224, 448, and 672 kg N ha**-1 were applied in 1999 and 2000. Nitrogen uptake varied by year because of contrasting environmental conditions. Averaged across N rate, orchardgrass and smooth bromegrass captured 799 and 555 kg N ha-1 during the 2-yr period. Orchardgrass fertilized with the medium and high N rates accumulated 13 and 14% more N than plants fertilized with the low N rate in 1999 and 32 and 36% more N in 2000, compared to 9 and 17% and 30 and 38% in smooth bromegrass. Residual soil NO3-N fluctuated according to N uptake and cumulative N input. In 1999, soil NO3-N levels after a killing frost were 5, 36, and 67 mg kg-1 at the low, medium, and high N rates in the top 0.6 m of soil in orchardgrass and 13, 44, and 72 mg kg**-1 in smooth bromegrass, compared to 2000, when concentrations of 2, 6, 40 and 3, 5, and 27 mg kg**-1 were measured. Orchardgrass N uptake potential exceeds that of smooth bromegrass and represents a good choice for rapid capture and removal of excess N.