Nitrogen Effects on Monostands and Polystands of Annual Bluegrass and Creeping Bentgrass

Abstract

Annual bluegrass (Poa annua L.) and ‘Penncross’ creeping bentgrass (Agrostis palustris Huds.) were grown in monostand and polystand in silica sand and supplied with solutions in which 0%, 25%, 50%, 75% or 100% of the N was NH4+ and the remainder was NO3.– In polystand, annual bluegrass was more competitive than ‘Penncross’, producing more shoot and root dry weight and more tillers. Competitive ability of annual bluegrass was decreased as the percentage of NH4+ increased in nutrient solution. The decrease in competitive ability was reflected by a decline in tiller number and root and shoot dry weight. ‘Penncross’ was less affected by N form than was annual bluegrass.

Nitrate and Ammonium Nitrogen Effects on Growth of Creeping Bentgrass and Annual Bluegrass

“…The green house was maintained at ~21C in the day and 16C at night. The pH in the silica sand rootzone was not controlled or monitored during the experiment; in a simultaneous ex periment using the same species, substrates, and treatment solutions, the rootzone pH showed a small but statistically significant decrease with increasing NH^-N, from 7.1 to 6.5 (Eggens and Wright, 1985).…”

“…Nitrogen source may also affect the competitive bal ance between annual bluegrass and creeping bentgrass. Annual bluegrass appears to grow more slowly and be less competitive when N O 3-N is the predominant source (Eggens and Wright, 1985;Engel and Busey, 1979;Waddington et al, 1978), whereas creeping bentgrass may be less affected by N source (Markland and Roberts, 1969;Mazur and Hughes, 1976). Little information has been available on variation among creeping bent grass cultivars in response to differing N sources.…”