1 Nitrogen absorption and movement in creeping bentgrass Agrostis stolonifera as affected by nitrogen source and shade E. Nangle*, D. Gardner, A. Studzinska, K. Danneberger, J. Street *Dept. of Horticulture and Crop Science, 2021 Coffey Road, The Ohio State University, Columbus, OH 43210-1086; Keywords: foliar application, nitrogen movement, shade management. Introduction Shade on turfgrasses leads to leaf elongation and thinning of the turf surface. Management of shaded turf areas is affected by many variables including air movement, the percent shade, the type of shade and time of day. Strategies which have been investigated include the use of growth regulators (Steinke and Stier, 2003; Wherley et al., 2005) and different sources, forms and rates of nitrogen (Goss et al., 2002). The aim of these investigations is to alter plant growth in a way that reduces leaf elongation and reduces loss of surface quality (Beard, 1997). Nitrogen is required for maintaining suficient turfgrass quality since it is an essential component of many plant compounds required for growth and development (Fry and Huang, 2004). Nitrogen movement into turfgrasses has had minimal investigation and no research has looked at uptake of nitrogen sources in shaded conditions. In full sun (FS) conditions using perennial ryegrass, Bowman and Paul (1992) found that KNO 3 , (NH 2 ) 2 CO and (NH 4 ) 2 SO 4 entered at a similar rate when applied to the leaf. This research showed that the partitioning of N varied between leaves and roots. Henning et al., (2009) found a similar result on creeping bentgrass while Stiegler et al., (2009) found that (NH 2 ) 2 CO was taken up in greater amounts in comparison to other N sources also on creeping bentgrass. It is unknown how these fertilizers act in shaded conditions, however, and the objective of this research was to investigate if there is a difference in nitrogen uptake from foliar fertilizer applications to shaded creeping bentgrass (Agrostis stolonifera) Materials and methods Greenhouse trials were conducted at The Ohio State University, Department of Horticulture and Crop Science greenhouses, Columbus, Ohio on 2-5 July and 24-27 July, 2007. Two hundred and forty pots ~12.5 x 20cm size were illed with 12 x 15 cm plugs of creeping bentgrass from the ield and illed with 80/20 w/v sand/soil rootzone. The trial areas were in split plot design. The light environment was the main treatment and N sources the subplots, with three replications and two experimental repetitions. The pots were placed in a FS environment and under a 10-12 week-old soybean (Glycine max) canopy (DS), replicating a deciduous tree canopy. The R:FR ratio measured .45 under DS and 1.23 in FS using a spectroradiometer (LiCor-1800). The shade in the canopy showed some variation but averaged <20% photosynthetic photon lux of FS. The three sources of N, Ca(NO 3 ) 2 ,(NH 4 ) 2 SO 4 and (NH 2 ) 2 CO were labeled with 15 N (Sigma Aldrich) and applied at a rate of 0.43g m 2 . The Ca(NO 3 ) 2 carried 99% label, (NH 4 ) 2 SO 4 and (NH 2 ) 2 CO were 60% each. Pots were placed in an area of 3.3 m 2 and application was made with a CO 2 backpack sprayer. Immediately after the irst application and again at 6, 12, 24, 48 and 72 hours after treatment (HAT) plants were