Submitted to: American Society of Agronomy
Publication Type: Abstract Only
Publication Acceptance Date: November 3, 1996
Publication Date: N/A
Technical Abstract: N use efficiency components were evaluated for seven warm species for use as vegetative filter strips. Plots established since 1991 received repeated applications of broadcast fertilizer. Each year plants were either periodically cut or left uncut until dormant. Before applying 15N-depleted fertilizer in April 1995, inorganic N in soil profiles was measured. Substantial N was found in the upper 105 cm of soil (135+13 kg/ha), but differences among species and cutting management were not significant or different from fallow plots (142+14 kg/ha). Distribution patterns, however, differed; inorganic N was abundant near the surface of plots with vegetation but uniformly distributed in fallow plots. Fertilizer N use efficiencies ranged from 10 to 52% and were increased by periodic cutting. Lower recoveries in uncut plants allowed to go dormant may be partly due to lower yields, losses of plant parts (seed and leaf), and mobilization of aboveground N to root tissues. Alamo switchgrass (Panicum virgatum L.) among the most productive species had the greatest fertilizer N efficiency. Among the cut plots, biomass produced per unit of plant N was greatest for Aztec Maximilian sunflower (Helianthus maximilianii Schrad.); differences among species in biomass produced per unit of absorbed fertilizer N were not significant. Those species that produce the greatest biomass and show favorable persistence with cutting and perhaps grazing, should be the best species for N attenuation in vegetative filter strips of the Rolling Plains area of Texas and Oklahoma.