Annual bluegrass and creeping bentgrass response to varying levels of iron

Abstract

Many biotypes of annual bluegrass (Poa annua L.) are found on golf course putting greens. Although normally considered an invasive weed, annual bluegrass can provide as good a putting surface as creeping bentgrass (Agrostis palustris Huds.). The most desirable biotypes of annual bluegrass are primarily vegetative and have a low flowering frequency. Whether the nutritional requirements of annual bluegrass biotypes differ from one another or from creeping bentgrass is unknown. The response of three flowering (FAB, high seedhead production) and three vegetative (VAB, low seedhead production) biotypes of annual bluegrass (AB), and the three parents of 'Penncross' creeping bentgrass (CB) to varying levels of iron (Fe) in greenhouse sand culture was investigated. After establishment, clones were grown for 3 weeks and irrigated with a strength Hoagland's solution containing 0, 2, 4, 6, and 8 mg·L-1 Fe in citrate-Fe. Shoot and root responses to Fe were similar for the VAB and FAB biotypes. However, VAB had higher color ratings (darker green leaf color) with Fe treatment level at 4 mg·L-1 than did FAB or CB, which required 6 mg·L-1 Fe for acceptable color. Growth of creeping bentgrass was greater than that of annual bluegrass at every Fe level tested. Shoot dry weights of CB increased significantly with Fe treatment level up to 6 mg·L-1. Shoot dry weight of AB increased up to 4 mg·L-1 Fe and then declined at ≥6 mg·L-1. Root growth of CB increased up to 6 mg·L-1 Fe, but then decreased significantly at 8 mg·L-1 Fe. Root growth of AB increased slightly up to 4 mg·L-1 Fe and then declined at 6 and 8 mg·L-1. Shoot tissue concentrations of Fe were similar for AB and CB at each Fe rate tested except at 8 mg·L-1 Fe, where Fe levels in CB were significantly lower. Based on this work, creeping bentgrass and annual bluegrass respond differently to Fe nutrition, but different biotypes of annual bluegrass appear to respond similarly.