The integration of cover crops into cropping systems brings costs and benefits, both internal and external to the farm. Benefits include promoting pest‐suppression, soil and water quality, nutrient cycling efficiency, and cash crop productivity. Costs of adopting cover crops include increased direct costs, potentially reduced income if cover crops interfere with other attractive crops, slow soil warming, difficulties in predicting N mineralization, and production expenses. Cover crop benefits tend to be higher in irrigated systems. The literature is reviewed here along with Michigan farmer experience to evaluate promising cover crop species for four niches: Northern winter (USDA Hardiness Zones 5–6), Northern summer (Zones 5–6), Southern winter (Zones 7–8), and Southern summer (Zones 7–8). Warm season C4 grasses are outstanding performers for summer niches (6–9 Mg ha−1), and rye (Secale cereale L.) is the most promising for winter niches (0.8–6 Mg ha−1) across all hardiness zones reviewed. Legume–cereal mixtures such as sudangrass (Sorghum sudanese L.)–cowpea (Vigna unguiculata L) and wheat (Triticum aestivum L.)–red clover (Trifolium pretense L.) are the most effective means to produce substantial amounts (28 Mg ha−1) of mixed quality residues. Legume covers are slow growers and expensive to establish. At the same time, legumes fix N, produce high quality but limited amounts (0.5–4 Mg ha−1) of residues, and enhance beneficial insect habitat. Brassica species produce glucosinolate‐containing residues (2–6 Mg ha−1) and suppress plant‐parasitic nematodes and soil‐borne disease. Legume cover crops are the most reliable means to enhance cash crop yields compared with fallows or other cover crop species. However, farmer goals and circumstances must be considered. If soil pests are a major yield limiting factor in cash crop production, then use of brassica cover crops should be considered. Cereal cover crops produce the largest amount of biomass and should be considered when the goal is to rapidly build soil organic matter. Legume–cereal or brassica–cereal mixtures show promise over a wide range of niches.

Glyphosate-resistant alfalfa offers new weed control options for alfalfa establishment. Field studies were conducted in 2004 and 2005 to determine the effect of establishment method and weed control method on forage production and alfalfa stand establishment. Seeding methods included clear seeding and companion seeding with oats. Herbicide treatments included glyphosate, imazamox, imazamox + clethodim, and no herbicide. Temporary stunting from the glyphosate treatments was observed (< 7%); however, injury did not reduce forage yield or stand density in 2004. No glyphosate injury was observed in 2005. Weed control with glyphosate was more consistent than with imazamox or imazamox + clethodim. In 2004, total seasonal forage yield, which consisted of alfalfa, weeds, and oats (in some treatments), was the highest where no herbicide was applied in the oat companion crop and was reduced where herbicides were applied in both establishment systems. In 2005, seeding method or weed control method did not affect total seasonal forage production. Alfalfa established with the clear-seeded method and treated with glyphosate yielded the highest alfalfa dry matter in both years. Imazamox injury reduced first-harvest alfalfa yield in the clear-seeded system in both years. When no herbicide was applied, alfalfa yield was higher in the clear-seeded system. The oat companion crop suppressed alfalfa yield significantly in both years. Alfalfa established with an oat companion crop had a lower weed biomass than the clear-seeded system where no herbicide was applied in both years.

Consolidation in the dairy and livestock industry in the North Central stateshas resulted in a need for producers to increase forage production per unit ofland base. Using a winter annual forage crop in a corn (Zea mays L.) andsoybean [Glycine max (L.) Merr.] cropping system could add a thirdharvestable crop in a two‐year rotation period resulting in increased forageproduction per unit of land base. The objective of this study was to: (1)evaluate the yield and quality of winter wheat (Triticum aestivum L.) andrye (Secale cereale L.) crops harvested as an early spring forage; and (2) evaluate the affect on subsequent rotational crop yield. Winter wheat andrye forage yielded from 2.7 to 1.7 ton/acre. Winter wheat and rye forage reducedyields of subsequently planted corn and corn silage compared to treatments thatdid not have a double‐crop winter annual forage. However, soybean yield was notreduced when preceded by the winter annual forage. These results suggest thatgrowers can effectively utilize winter wheat or rye as a double‐crop forage incorn‐soybean cropping systems when the winter annual forage crop precedessoybean in the rotation.

The lack of a definitive method to assess winter hardiness in alfalfa (Medicago sativa L.) remains a challenge in the north‐central region of the USA where winterkill of alfalfa can be severe. The reliability of fall dormancy ratings for describing alfalfa cultivar susceptibility to winter injury and the role of snow depth in moderating temperatures near the plant were investigated at Chatham, MI on a Chatham Stony loam (Typic Haplorthod). Four cultivars were selected with a range of fall dormancy ratings: ‘Nitro’, ‘Magnum IV’, ‘Saranac’, and ‘Vernal’. The cultivars were planted in 1993–1994, 1994–1995, and 1995–1996 seasons in plots over which 0‐, 10‐, and 20‐cm winter snow depths were maintained. Temperatures were monitored for each plot, and stand counts were made each fall and spring to assess winter injury. Nitro suffered the most winterkill across snow cover treatments. The total yield range was 0 to 9 Mg ha−1 in the absence of a snow cover and 0.4 to 12 Mg ha−1 for a snow depth of at least 10 cm, except in 1996. Extreme minimum canopy‐level (6 cm) temperatures for 10‐cm snow depth averaged over three winter seasons were 12.1°C higher than the 0‐cm snow cover treatment, which translated into higher yields. The results suggest that snow cover of 10 cm adequately protects alfalfa from winter injury. Cultivars within the same fall dormancy rating did not necessarily perform similarly, suggesting the need to develop other methods for assessing winter survival.

High temperatures and scarce precipitation often cause the productivity and quality of cool‐season pastures in Southwest Michigan to decline for an extended period during the summer. This study was conducted to determine whether integration of switchgrass (Panicum virgatum L.) or big bluestem (Andropogon gerardii Vitm.) into cool‐season grazing systems would mitigate this period of low pasture productivity and quality. Cool‐season grass and legume pastures (CS‐Only) were compared to integrated big bluestem and cool‐season grass and legume pastures (CS‐BBS) and integrated switchgrass and cool‐season grass and legume pastures (CS‐SG). The seasonal dynamics of forage dry matter offered, crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF) were used to compare the dynamics of the pasture productivity and quality in each of three treatments. Dry matter offered in the CS‐Only treatment was higher earlier in the grazing season and the peak in dry matter‐offered occurred between 20 and 30 d earlier in the CS‐Only treatment than in the other treatments. The seasonal trend for CP was generally higher and more constant for the CS‐Only treatment than for the CS‐BBS and CS‐SG treatments, which were very similar to each other. The seasonal trend for ADF and NDF was generally lower and more constant for the CS‐Only treatment than for the CS‐BBS and CS‐SG treatments, which were very similar to each other. These findings suggest that, compared to the CS‐Only treatment, the CS‐SG or the CS‐BBS treatments probably will not improve livestock gain or improve the distribution of animal grazing days throughout the summer.