Harvest management is an important tool in achieving high-quality forage, high yields, and stand persistence. Harvest management can also be used to reduce the impact of weeds, insects, and diseases. Harvest timing is a compromise between forage yield, quality, and persistence. While forage quality decreases with maturity, dry matter yield usually increases up to fullflower stage in legumes and full-heading stage in grasses. Cutting more frequently at earlier stages of maturity results in forage with higher nutritive value but lower yield compared with cutting less frequently at more mature stages of growth.
A good compromise between forage yield, quality, and stand persistence is to harvest legumes in late-bud to early-bloom stage, and grasses in late-boot to early heading stage. Harvesting at that stage will result in the highest yields of digestible dry matter per acre. Cutting management of grass-legume mixtures should be based on the best harvest schedule for the legume.
First Harvest Timing
Make a timely first harvest to achieve the best quality possible in what is usually the largest crop of the year. Forage quality declines more rapidly with advancing maturity in the spring than it does later in the summer. Timing of the first harvest should be based on the calendar rather than on stage of maturity. Bud development and flowering are not reliable guides for proper timing of first cutting in Ohio. In some seasons, little or no bloom is present; in others, bloom is abundant. Table 7.10 gives recommended harvest dates for the first cutting of legume-grass hay meadows. Harvesting during these periods maximizes yields of digestible dry matter per acre. By using various grasses and legumes that differ in maturity development (Table 7.2), producers can spread the optimum first cutting date over one week to 10 days.
Most grasses should be harvested in the boot stage for best forage quality; however, timothy and smooth bromegrass should not be cut until the grass is in the early heading stage. Earlier harvesting of those species may reduce regrowth and result in stand loss, because the basal buds for regrowth are not fully developed until early heading.
A good method to time first cutting of alfalfa is described in a fact sheet and video titled "Estimating alfalfa fiber content in the field,” both of which are available at forages.osu.edu/forage-management/harvest-storage.
Summer Harvest Timing
Stage of growth is usually a reliable guide for timing summer harvests of legumes. Generally, summer (approximately 35 days between cuttings) and half bloom for birdsfoot trefoil and red clover. High yields of good quality forage can be harvested if four cuttings are made on a 35-day schedule. Four cuttings of alfalfa can be made on soils with good fertility without any detrimental effects on the stand. Harvest schedules for legume-grass mixtures should follow closely to what favors the legume component. Smooth bromegrass and timothy are more compatible with less intensively managed stands (threecut schedule), while orchardgrass, perennial ryegrass, tall fescue, meadow fescue, and reed canarygrass are adaptable to more frequent harvesting.
Intensive Cutting for High Quality
More intensive frequent cutting schedules are desirable where high forage quality is important. Shorter harvest intervals will usually shorten stand life, especially of legumes. Allowing legume stands to reach early flower stage once during the season improves stand persistence. This can usually be achieved in late summer without great reductions in forage quality (forage fiber levels increase and forage nutritive value decreases at a slower rate in late summer than earlier in the year). Cutting intervals that are consistently shorter than 30 days stress legume stands because the plants do not fully replenish depleted energy reserves in the taproots and crowns. Fiber levels may be undesirably low when legumes are cut extremely early (pre-bud to very early bud stage). Some grass species can be harvested very intensively to achieve dairy-quality forage. Pure stands of orchardgrass and perennial ryegrass (where adapted) can be maintained on harvest intervals of 24 days under good fertility management.
Fall Harvesting
Producers often want to harvest the fall growth from forage stands, but fall harvesting usually increases the risk of legume heaving and winter kill, and interferes with accumulation of root reserves required for winter survival and growth the following spring. The need for the forage or its value should be weighed against the increased risk of stand damage from fall harvesting.
Minimizing Fall Harvesting Hazard to Tall Legumes
• Complete the last regular harvest by the following dates: Sept. 7 in northern Ohio, Sept. 12 in central Ohio and Sept. 15 in southern Ohio
• Do not harvest during late September and October. Forages are actively storing reserve carbohydrates in the crowns and roots during this period
• If a late fall harvest is made, it should be delayed until after a killing frost (25 degrees Fahrenheit for several hours) or at least near to the time of killing frost. A word of caution: Removing topgrowth at this time can dramatically increase the risk of legume frost heaving on heavy soils. Mulching with up to 4 tons per acre of straw-manure or 2 tons per acre of old hay or straw should reduce frost-heaving potential after a late harvest. Late fall harvesting should only be attempted on healthy, established stands grown on well-drained soils with optimum pH and high fertility (high soil potassium levels are especially important)
• Avoid fall harvesting of new seedings
• If a mid-fall harvest is made, select fields that are well drained, have optimum pH and fertility, are planted to improved varieties having multiple pest resistance, and where at least 45 days of regrowth was allowed prior to the fall harvest.