Increasing costs associated with winter feeding have renewed interest in extending the grazing season in the North‐Central USA. A factorial design with three N treatments was applied to existing smooth bromegrass ( Bromus inermis Leyss.) pastures to evaluate initiation dates and N fertilization rates for stockpiling forage. Stockpile initiation dates were 1 June, 15 June, 1 July, 15 July, 1 August, and 15 August. Nitrogen fertilization treatments were 0, 56, or 112 kg ha −1 . Data collected included forage mass in October, residual forage mass the subsequent April, leaf concentration, and forage nutritive value. October forage availability was generally greater from earlier stockpile initiation dates (2.58, 2.44, 1.98, 1.28, 0.78, and 0.65 Mg dry matter ha −1 for 1 June, 15 June, 1 July, 15 July, 1 August, and 15 August stockpile initiation dates, respectively; LSD at 0.05 = 0.19). Leaf mass available in October was similar through the 15 July stockpile initiation date. October forage mass was greater with 56 kg N ha −1 than with 0 N fertilization, averaging 1.26, 1.75, and 1.85 Mg ha −1 (LSD at 0.05 = 0.14) for 0, 56, and 112 kg N ha −1 , respectively, when averaged across stockpile initiation dates and years. Trends in April forage mass for stockpile initiation date and N fertilization tended to be similar to October. Crude protein tended to increase and acid detergent fiber and neutral detergent fiber tended to decrease as stockpile initiation was later in the season. These results indicate that initiating stockpiling of smooth bromegrass–dominated pastures about 1 July with 56 kg N ha −1 optimizes stockpiled smooth bromegrass in the North‐Central region.

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.

Legumes can improve productivity and quality of cool-season grass pastures but often do not persist under grazing. In May of 1997 and 1998, field experiments were planted in cool-season grass pastures near Morris, MN, to evaluate establishment and persistence of kura clover ( Trifolium ambiguum Bieb.) compared with alfalfa ( Medicago sativa L.), birdsfoot trefoil ( Lotus corniculatus L.), and red clover ( Trifolium pratense L.) under grazing pressure in the north-central USA. Each spring, from planting through 2002, stands of these legumes were evaluated for persistence. Pastures were grazed five or six times per growing season for 12-h grazing periods by lactating dairy cows ( Bos taurus L.) over the duration of the study. Kura clover stand density was low relative to the other species in the growing season after establishment but increased and maintained denser stands in subsequent growing seasons. Alfalfa, birdsfoot trefoil, and red clover initially developed stands greater than 30% of the sward and remained constant or increased for two (1998 planting) or four (1997 planting) growing seasons before declining. In the spring of 2002, stands were greater ( P > 0.001) for both planting years for kura clover (90%) compared with alfalfa, birdsfoot trefoil, and red clover (41, 28, and 9%) when averaged across planting years, respectively. Kura clover stands spread 60 (1998 planting) to 90% (1997 planting) over the length of the study. Stands of other species did not spread. In these studies, kura clover was able to compete, persist, and spread under intermittent grazing and has the potential to be an important and persistent component of cool-season grass pastures in the north-central USA.

Legumes in cool‐season grass pastures can improve productivity and quality. In May of 1997 and 1998, a split‐split plot field experiment with six replications was planted in Morris, MN to evaluate the effect of sod suppression, planting method, and legume species on establishment of legumes into existing cool‐season grass pastures and to evaluate kura clover ( Trifolium ambiguum Bieb.) and birdsfoot trefoil ( Lotus corniculatus L.) as potential species for interseeding in the North Central region. Whole‐plot sod suppression treatments were (i) 0.62 kg a.i. ha −1 glyphosate [isopropylamine of N ‐(phosphono‐methyl) glycine] or (ii) no glyphosate. Subplot planting methods were (i) no‐till drilling, (ii) broadcasting seed on the soil, (iii) broadcasting seed followed by harrowing, and (iv) broadcasting seed followed by a light disking. Legume species sub‐subplots were (i) alfalfa ( Medicago sativa L.), (ii) red clover ( Trifolium pratense L.), (iii) kura clover, and (iv) birdsfoot trefoil. Stand data were collected in the fall of the planting year and in the spring of the second growing season. Averaged across planting methods and species, legume stands were 38% where glyphosate was used and 3% where it was not. No differences or interactions were detected for planting method ( P > 0.12). In this study, if competing vegetation was suppressed, stands were >31% regardless of planting method. When sod was suppressed, alfalfa established better stands than the other legume species. The overriding factor in the ability to establish legumes in this study was the suppression of existing vegetation during establishment.

Legumes have been shown to increase production in cool-season grass pastures. However, they are included he relatively few acres of pasture. A split plot experiment with six replications was conducted to evaluate the impact of pasture renovation and grazing management on forage production and species composition of cool-season grass pastures. Grazing management main plots were grazed to leave low (2-4 in.), medium (4-6 in.), or high (6-8 in.) residue levels, Main plots were intensively grazed (50 000-70 000 lb of cows per acre) five or six times per grazing season by lactating Holstein cows, Subplot pasture renovation treatments were (i) an untreated check, or sprayed with glyphosate and interseeded with (ii) alfalfa (Medicago sativa L.) (iii) red clover (Trifolium pratense L.) and birdsfoot trefoil (Lotus corniculatus L.), or (iv) "graziers mix" (a mixture of legumes and grasses), Areas that were grazed to leave low residue level produced less forage mass (4.7 ton/acre) than areas grazed to medium (5.4 ton/acre) or high (5.5 ton/acre) residue levels. When averaged across years and grazing management treatments, renovated areas produced 1.8 ton/acre (46%) more forage than the control, Of interseeded species, alfalfa, red clover, and orchardgrass persisted through the study (more theta 25% of the dry matter in st least one of the pasture renovation treatments). By June 1998, thistle (Carduus and Cirsium spp.) was present in all treatments. Fewer thistle was present in areas that were grazed to leave low residue (10 sq yd) than high residue (18 sq yd) and in renovated areas (9 sq yd) than the control (22 sq yd). The additional forage produced as a result of pasture renovation cost from $8.07/ton to $12.81/ton. This study indicates that pasture renovation can be a valuable tool for increasing forage production in cool-season grass pastures.