AGiven the long and harsh winter, many farmers are seeing winterkill and damage in their forage fields this spring. If you have yet to inspect your fields, now is the time to begin. Grasses and legumes are beginning to grow and signs of damage can be seen more easily seen at this time.
Signs of injury and winterkill include stands that are slow to green up and uneven growth patterns in fields. To diagnose damage in a suspect field, examine the plant roots. This can be done by walking diagonally across the field and digging up shovel full of plants (4-6 inches deep) at regular intervals, about every 4-5 paces. The roots of each plant should be firm and the interior color should be white or cream colored. If the roots are soft and the interior yellow to brownish in color, it most likely was winter killed. For alfalfa, the majority of crown buds should be white or pink and firm throughout the bud. It is important to try and inspect as many plants as possible to determine the percentage of your stand and/or areas of your field that are injured.
For fields moderately affected by winter injury, different management practices than normal will be necessary to keep the stand in production. Consider allowing plants to mature longer before cutting, or in the case of legumes, allowing them to fully bloom before cutting if the damage is more severe. Increasing cutting height, leaving new shoots, and not cutting the stands in the fall will aid in the stand’s recovery and increase production. If alfalfa was lost in a predominately grass stand, it could be managed for grass. If the alfalfa stand was only partially injured (25 to 50%), interseeding with a quick germinating forage, such as orchardgrass or perennial ryegrass, could provide additional production. When dealing with winter injured stands, it is particularly important to adequately fertilize and to control for weed competition.
For fields severely affected by winter injury, such as over 50% killed, you may want to consider replanting. A small grain/field pea mixture or annual ryegrass will be good choices if the forage is needed in early/mid-summer. Corn silage will be the best choice for optimizing full season forage production, but at later dates (mid-June to early July) you may want to consider planting a summer annual. A few options include Sudangrass, sorghum, sorghum-sudangrass hybrids, and millet.
More information on managing winter injury in forages can be found in the following resources:
“Evaluating and Managing Forage Stands for Winter Injury” by NWCS, UVM Extension. https://www.uvm.edu/sites/default/files/media/managing-forage-winter-injury.pdf
“Managing Cereal Grains for Forage” by NWCS, UVM Extension. https://www.uvm.edu/sites/default/files/media/managing-cereal-grains-for-forage.pdf
“Evaluating Hay and Pasture Stands for Winter Injury” by Iowa State University Extension.