Assessing Forage Stands and Winter Damage

Spring is here and now is a great time to walk fields and note how the forages faired. Winter damage is difficult to predict and the variability of temperatures this past winter across the state can present some difficult conditions for forages. Depending on the location and what type of forage field, winter damage may be a major concern, particularly for forages with taproots like alfalfa. Stands should be assessed carefully during spring green-up for concerns such as heaving and crown and root disease. A thorough and timely assessment will allow for planning any necessary adjustments for the 2024 season.

Assessment

When making a stand assessment it is important to not only make aboveground observations by way of a stem count but to also dig up plant samples and assess the below-ground biomass. To make an aboveground assessment, select a random one square foot in the field and count the number of living stems within that square foot area. Repeat that random selection and counting of stems, 4-5 times for an area of 20-25 acres. When scouting the more samples or locations assessed the more accurate the estimate will be. The average stem density of a field can be a useful tool to gauge the yield potential for the coming year. For alfalfa stand assessments the University of Wisconsin Extension has a useful publication; “Alfalfa Stand Assessment: Is this stand good enough to keep?”, in which they provide the following table as a reference for stand assessment and decision making.

While assessing the stem density of a forage stand take note of where on the plant shoot growth is active. Healthy plants will have numerous shoots growing evenly around the crown. A damaged plant will have a lower number of total shoots and often have more or all stems on one side of the crown. Damaged plants will be lower yielding and have a lower survivability for the following winter.

Heaving

With temperature variability and freeze-thaw cycles, heaving is a common form of winter damage seen in the field. This is a more common problem in heavier clay soils and poorly draining soils. Warmer temperatures occurring sporadically in February and March, followed by short freezes, similar to what we have seen this year can heave and expose the root system to a severe enough level that plants may not survive into May. Plants that experience heaving and survive, are more susceptible to disease and the stress of heaving accumulates over the lifespan of the crop lowering the yield potential and life expectancy of the stand. If significant heaving is observed, but crown health is minimally affected adjustments to harvest practices prior to the first cutting may be necessary. Cutting too low at any point during the year on heaved crowns can not only damage the crown and slow regrowth but can also damage the root system, often causing immediate death and no additional cuttings. Making obvious notes in the mower tractor or flagging the field enterance can help you remember throughout the year that mower adjustments need made to not damage the stand. Stand with increased heaving may be limped through this year by managing cutting but will usually need to be rotated to another crop next year.

Stem and Root Concerns

Even if no heaving is observed it is important to dig up plant samples and observe crown and root health. Similar to assessing stem density, select multiple random plants and split the crown and root. The table below can help you rate crowns. A healthy stand will have less than 30% of crowns rating 3 or 4 and no crowns in the count rating 5, which are dead plants.

Once a stand assessment is completed, if renovations are needed there are a couple of options. Stands can be improved with grasses and clover to extend the production of the forages for a few years. Another option is terminating after a first cutting and plant silage corn or possibly a warm season forage such as sorghum, sudangrass, or sorghum-sudan as a high-yielding alternative to meet forage production needs. Based on your operation practices, options such as Teff grass, Italian ryegrass, or Berseem clover are good options for dry hay.  Summer annual cereal grain forage such as oats, spring triticale, or spring barley could be made as dry hay but may be easier to harvest as silage or baleage. To fulfill forage needs, spring seeding alfalfa is an option, and planted with a companion crop can provide forage this year and set up a stand ready for maximum yield next year.