Impact of Nitrogen Source and Trinexapac-ethyl Application on Creeping Bentgrass (Agrostis stolonifera L.) Physiology under Neutral Shade, Deciduous Tree Shade, and Full Sunlit Conditions

Abstract

Decreased light quantity or quality affects the growth of turfgrass plants. Shade causes thinning of turfgrass stands and loss in surface quality. Plant changes include increased chlorophyll levels, lower soluble sugars, and loss of canopy cover. The objective of this research was to investigate if applications of foliar nitrogen and trinexapac-ethyl [4-(cyclopropyl-α-hydroxy-methylene)-3,5-dioxo-cyclohexane carboxylic acid ethyl ester] (TE) would result in beneficial biochemical changes in creeping bentgrass (Agrostis stolonifera L. cv. Penncross) grown in different shaded environments. Foliar applications of three nitrogen treatments, (NH2)2CO, Ca(NO3)2, or (NH4)2SO4, were made weekly at 0.43 g N/m2. Growth regulator treatments consisted of an untreated control or TE applied biweekly at an a.i. rate of 0.057 kg·ha−1. Plots were established in full sun (FS), neutral shade (NS), and deciduous shade (DS). Chlorophyll content, soluble carbohydrates, flavonoids, clipping yield, and color were measured. Nitrogen treatments caused some variation in levels of soluble carbohydrates in shaded conditions. Chlorophyll (Chl) levels varied between TE treatments, with increased levels of chlorophyll b (Chl b) found in TE-treated plots under FS. Application of TE resulted in higher flavonoid concentrations in leaf tissue in shaded conditions. Repeated applications of (NH2)2CO significantly improved color (P = 0.05). Turfgrass managers maintaining creeping bentgrass in shade may benefit from applications of TE and (NH2)2CO.