Submitted to: Crop, Forage & Turfgrass Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/15/2015
Publication Date: 6/26/2015
Citation: Bartholomew, P.W. 2015. Timing of nitrogen fertilizer application for annual ryegrass overseeded into unimproved perennial warm-season pasture. Crop, Forage, & Turfgrass Management. doi:10.2134/cftm2013.0018.
Interpretive Summary: In the southern Great Plains (SGP) cool-season grasses overseeded into dormant warm-season pasture can provide grazing at a time of year when green forage is usually not available. However, as warm-season pasture growth resumes in spring there may be competition between cool and warm-season grasses that results in reduced yield of warm-season grasses and offsets some of the yield benefit provided by the cool-season crop. This problem arises, in part, because of delayed spring growth and late termination of growth of the cool-season grass. Experiments were undertaken to determine whether oats or rye would provide earlier production and shorter growth cycle than annual ryegrass and, if increased N fertilizer in spring would accelerate cool-season production sufficiently to offset negative effects on warm-season grass later in spring. Oats were not sufficiently cold-hardy to survive over winter. Increased N application in early spring did not increase early season production in rye or annual ryegrass. Annual ryegrass was more productive than rye throughout, but the response to increased N application was similar in both crops, ranging from 9.2 to 32.3 lb dry forage per 1 lb of N applied. Sown at the recommended seed rate rye was less productive than annual ryegrass, but was more costly to establish. Increased spring N application increased overall forage yield but did not advance the spring growth period of rye or annual ryegrass and did not have any apparent effect on competition between cool- and warm-season grasses.
Technical Abstract: In the southern Great Plains fall overseeding of annual forages can increase herbage production early in the following year, but competition between cool- and warm-season components of mixed pasture may result in only small net benefit in total annual yield. Increased seasonal separation of pasture components, by use of early-producing species, or by stimulation of early growth by N fertilizer application to the cool-season crop, may mitigate problems of competition. Rye (Secale cereale L.), oats (Avena sativa L.) or annual ryegrass (Lolium multiflorum Lam.) were overseeded into dormant unimproved warm-season pasture in fall and provided 25, 50 or 75 kg/ha of N fertilizer in mid-February of the following year. Oats did not tolerate low winter temperatures. Rye was more difficult to establish under no-till conditions than ryegrass and provided no clear benefit in early-season production. Rye and annual ryegrass showed similar DM yield responses to applied N but, at harvest in early April, response to increased N application was less than 4.0 kg DM per kg N applied, and neither species showed significant advance in early-season growth. N application treatment or species choice had little impact on DM yield of the warm-season grass component of mixed cool- and warm-season pasture.