Craig C. Sheaffer, University of Minnesota

The information presented in this fact sheet is not intended to take the place of professional legal advice. In developing any written lease agreement, it is highly recommended that all parties seek professional legal advice.

Summary

• Fifteen to 30 percent of the standing forage crop is commonly lost during harvest and storage. Field losses are greater for hay, while storage losses are greater for silage.
• To develop sound harvest strategies, farmers should understand how plant development relates to forage yield, quality, and persistence.
• Scheduling the harvest based on stages of plant development is the most reliable way to obtain the desired yield and quality consistently.

Hay and Silage

Harvested forage is usually stored as hay or silage. Hay is stored at a moisture level below 20 percent. When farmers store hay at moisture levels higher than 20 percent, the forage becomes moldy and may spontaneously catch on fire. For best long-term storage, hay should be sheltered from rain or snow.

Silage is forage preserved in an anaerobic (without air) environment with a pH of 3.6 to 5.0. Specialized storage structures or wrappings meet these conditions. Silage is made by fermentation at moisture levels between 40 and 85 percent. Silage stored at a 40 to 60 percent moisture level is called haylage. Wilted silage has a moisture level of 60 to 75 percent. Direct cut, unwilted silage has a moisture level of 70 to 85 percent.

Harvest and Storage Losses

On average, farmers lose from 15 to 30 percent of the standing crop during harvest and storage. Field losses are typically greater for hay than silage, due to greater field exposure and handling of forage at a lower moisture level. Field losses can result from mechanical action and handling, plant and microbial respiration, or exposure of cut forage to rain. Because leaves dry faster than stems, leaves may shatter during field operations. Therefore, much of the lost dry matter is high-quality leaves.

Storage losses are much greater for silage than for hay. Storage losses are due to plant and microbial respiration, undesirable fermentation, and spoilage. Recommended hay and silagemaking practices are found in Tables 1 and 2.

How Plant Development Relates to Forage Yield, Quality, and Persistence

To develop sound harvest strategies, farmers should understand forage legume and grass development and the relationship to forage yield, quality, and stand persistence. Stages of grass and legume growth are described in Tables 3 and 4 and in Figure 1.

Plant development and forage yield
Forage yields accumulate rapidly from the vegetative stage to early flowering in legumes and until dough stage in grasses. While yields can continue to increase in later stages, they often increase more slowly due to the loss of leaves from the plants’ lower stems. In the vegetative stage, the proportion of leaves is equal to or greater than that of stems. However, during flowering, the proportion of stems exceeds that of leaves. When to harvest depends on farmer goals (see “When to Harvest” ).

Plant development and forage quality
Forage quality is described in terms of nutrient concentration (e.g., crude protein, minerals), animal intake potential (e.g., neutral detergent fiber), and palatability (Tables 5 and 6). Forage quality is highest when legumes and grasses are in the vegetative (immature) stage. As plants age, nutrient concentration and intake potential decline. The proportion of leaves drops as plants mature. Any reduction in leaf proportion relative to stems decreases forage quality, since leaves are more nutritious than stems.

Plant development and carbohydrate reserves of the root and crown
Carbohydrate reserves provide energy for regrowth and other metabolic processes such as respiration. Plants with high energy reserves often persist better. Plants store and use reserves in a cyclic pattern, where energy drops when regrowth begins and accumulates until plants start to flower. Therefore, while cutting grasses and legumes at the vegetative (immature) stage may produce high quality forage, it usually reduces their long-term persistence. (For more information on the persistence of legumes and grasses in CRP fields, see Persistence of Planted Forages in this series.)

When to Harvest

Scheduling the harvest based on stages of plant development is the most reliable way to obtain the desired yield and quality consistently. By using the stage of growth as a signal for when to harvest, this approach takes into account differences in the weather from one year to the next. Alternatively, scheduling each year’s harvest at the same fixed intervals or on the same dates makes it easier to coordinate the harvest with other field activities. In practice, many farmers combine both approaches to harvesting. For example, a first cutting in late May or early June can help avoid delays in harvesting brought on by inclement weather later in the season.

Recommended harvest schedules vary with farmer goals. If farmers are seeking high forage quality, they should cut legumes at the bud stage and grasses at the boot stage. However, if a high nutrient yield-per-acre is the goal, legumes should be harvested at early flowering and grasses at heading or flowering. For legume-grass mixtures, cutting schedules are usually based on the predominant plant. Cool season forages should be harvested to a 1- to 3-inch stubble height for maximum yield. Leaving more stubble benefits only stressed or winter-injured stands. Warm season grasses should be harvested to an 8- to 10-inch stubble height.

Differences Among Grasses and Legumes
Grasses and legumes differ in their ability to adapt to various soil conditions, climatic conditions, and harvest schedules. (See Renovating Land for Forage Production in this series.) Grasses tend to adapt better than legumes to stressful defoliation (frequent cutting or grazing at vegetative stages and to a low stubble height) and environmental extremes.

Grasses and legumes also differ in forage yield potential. Under good growth conditions and high rates of nitrogen fertilization, different species of tall-growing cool season grasses typically have similar yield potentials, with a maximum yield of about 6 tons per acre. Legume species, however, differ greatly from one another in yield potential. Under optimum soil and environmental conditions, alfalfa yields can approach 8 tons per acre. Usually, however, maximum yields are about 5 to 6 tons per acre. Yields of other perennial legumes are lower (see Other Resources #4).

Grasses and legumes also differ in forage quality (see Tables 5 and 6). Legumes usually have a higher nutrient concentration and greater intake potential than grasses. Some weeds, such as quackgrass, can be excellent sources of forage similar in quality to more commonly grown forage grasses.

Other Resources

1. Silage and Hay Preservation (1990). Northeast Regional Agricultural Engineering Service, Cooperative Extension, 152 Riley-Robb Hall, Ithaca, NY 14853 • 607-255-7654.
2. Warm Season Perennial Forage Grasses: Big Bluestem and Switchgrass. (USDA -Natural Resources Conservation Service, 1995). Available from the Minnesota Department of Agriculture, Sustainable Agriculture Program, 625 Robert St. N, Saint Paul, MN 55155-2538 • 651-201-6673.

The following publications are available from your local Minnesota Extension Service (MES) office or the MES Distribution Center, University of Minnesota, 20 Coffey Hall, 1420 Eckles Avenue, Saint Paul, MN 55108-6069. 612-624-4900 or 1-800-876-8636.

1. Reed Canarygrass (1990), #ES-SB-5533.
2. Forage Legumes (1993), #ES-SB-5963.
3. Alfalfa Management Guide (American Society of Agronomy, 1994), #AG-BU-5798

MDA Contact

Barbara Weisman, Conservation Program Specialist
barbara.weisman@state.mn.us
651-201-6631 or 1-800-967-2474
Ag Marketing & Development Division