Nitrogen Fertilization Impacts on Stand and Forage Mass of Cool-Season Grass-Legume Pastures

Abstract

Combining the benefits of legume N2fixation and N fertilization may increase the productivity and profitability of pasture systems. Our objectives were to study the effects of N fertilization on productivity and persistence of legumes in mixtures with cool‐season grasses under rotational stocking with short grazing periods. Twelve N fertilization regimes ranging from 0 to 336 kg of N per ha were applied annually to smooth bromegrass and reed canarygrass in monoculture and mixture with alfalfa, birdsfoot trefoil, and kura clover. Alfalfa was the dominant legume in mixtures with cool season grasses in 1999. As kura clover developed, it became the dominant legume species and by the trials end stands averaged over 70% in mixtures with both smooth bromegrass and reed canarygrass and across N treatments. Nitrogen fertilization did not affect alfalfa stands, but reduced kura clover stands by 17%. Smooth bromegrass‐legume mixtures with no N fertilization produced more forage (10.5 Mg DM/ha) than any smooth bromegrass monoculture with N treatment (336 kg of N per ha produced 8.0 Mg DM/ha). Cost of forage mass in smooth bromegrass‐legume mixtures was less than 50% of smooth brome monocultures. While N fertilization did not increase forage production in treatments with legumes, legumes were able to maintain vigorous stands with up to 336 kg of N per ha.

Kura Clover Forage Yield Contribution Increases Over Time When Seeded in Mixture with Grasses in Southwestern Québec

“…The high clover:grass ratios observed in the spring of the fifth post‐seeding year for all KC‐grass mixtures could potentially be problematic for grazing animals, KC having the potential to cause bloat (10,15). Such results are in accordance with previous studies, which also reported a gradual increase in KC contribution to total forage yield, and a propensity for KC to dominate swards several years after seeding (1,2,6,16). The present study suggests that KBG should not be seeded with KC in southwestern Québec, since it does not have the ability to sufficiently contribute to yield in proportions (i.e., at least 50%) that would limit bloat potential (4).…”

“…Despite its great potential, KC use remains marginal mainly due to a characteristic slow development (3,5,6,13,14). Kura clover's contribution to yield is initially minimal; it however gradually increases in post-seeding years (1,2,5,6). If KC's development pattern is well known, there is however limited information on how KC yield contribution over time may differ when seeded with various grass species.…”

Overseeding aeschynomene and N fertilization effects on forage characteristics, N fixation, and N2O‐N emissions of bahiagrass pastures

“…Cuomo et al. (2005) observed that persistence of alfalfa ( Medicago sativa L.) and birdfoot trefoil ( Lotus corniculatus L.) was not affected by the application of 56 kg N ha −1 when overseeded into reed canarygrass ( Phalaris arundinacea L.), but the N increased grass forage accumulation and nutritive value.…”

“…Although previous studies reported a negative effect of N fertilization on overseeded legumes (Mulder, 1952;Robinson & Sprague, 1947), studies with cool-season species demonstrated that low N fertilization levels may stimulate grass growth without impacting legume performance. Cuomo et al (2005) observed that persistence of alfalfa (Medicago sativa L.) and birdfoot trefoil (Lotus corniculatus L.) was not affected by the application of 56 kg N ha −1 when overseeded into reed canarygrass (Phalaris arundinacea L.), but the N increased grass forage accumulation and nutritive value.…”

Enhanced efficiency nitrogen formulations for bermudagrass–white clover pastures

“…Previous research has shown legume tolerance to N applications up to 150 kg N ha −1 (Gardner et al., 1960; Mackenzie & Daly, 1982; Hoveland et al., 1995; Harris & Clark, 1996; Cuomo et al., 2005). Nitrogen application up to 112 kg N ha −1 did not suppress ladino clover in orchardgrass ( Dactylis glomerata L.) when applied as split applications across the growing season (Nelson & Robins, 1957).…”