Doo-Hong Min, Department of Crop and Soil Sciences, MSU Extension
Richard Lee, Department of Crop and Soil Sciences, MSU Extension
(Previously published on MSU Extension, Crop Advisory Team Alerts: September 18, 2008)
(Image Source: Texas A&M University)
Among the four seasons, fall is one of the most important seasons in terms of preparing for winter survival and spring regrowth by storing carbohydrate and protein reserves in the crowns and roots. Fall is also the season for regeneration and the formation of the shoots or growing points. Since plants become dormant in the fall as air temperature is getting lower and day length is shorter, nutrient uptake becomes accordingly slower. The following are points to consider for fall forage management for hay and pasture:
1.) Soil fertility and liming:
Since the price of fertilizer is so high these days, it’s important to use phosphorus (P) and potassium (K) efficiently. One of the best ways to save fertilizer costs is to test soil phosphorus and potassium on the hay fields and pasture. In particular, potassium is directly related to winter survival rate and it’s more susceptible to winter kill when soil potassium level is lower than the optimum level.
Fall is also a good time for liming. Having optimum soil pH is a key to having a healthy forage stand. Grasses generally perform well at a pH of 6.0 or above while most legumes require a pH of 6.5 or more. With low soil pH, plant growth can be very poor caused by poor nutrient uptake, which results inpoorer winter survival and more weed problems. This can also result in poor animal performance from low forage yield and nutritive value. Since increasing soil pH is a long-term process, it’s important to apply lime materials at least 6-12 months before the results can be shown, depending on the fineness of lime materials (the higher mesh numbers, the quicker response). It’s good to have fine lime materials, particles that pass a 100-mesh sieve react 100% with the soil in 6 months or less, to increase the soil pH in a short time period. In summary, it’s very critical to test the soil before putting any phosphorus, potassium, or liming materials to the forage fields.
2.) Fall harvest management of alfalfa:
In the late summer and early fall, alfalfa must either be cut early enough so it can regrow and then replenish root carbohydrates and proteins, or so late that the alfalfa does not regrow more than 8 inches and use root carbohydrates. This has resulted in the recommendation in Michigan of a “no-cut” window beginning in September and lasting until the killing frost. However, recent research in Quebec, Canada has helped to redefine this window by assuming that if 500 growing degree days accumulate after the last cutting, there will still be enough regrowth of alfalfa for good carbohydrate accumulation before a killing frost and good winter survival and yield the following year. So a producer can cut in September without hurting the stand as long as there is enough warm weather remaining in the growing season (accumulation of 500 growing degree days) before a killing frost. These growing degree days are calculated as the average of the daily minimum and maximum above 41°F until a killing frost of 25°F. The Quebec research also showed that cutting later in the fall was acceptable as long as less than 200 growing degree days accumulated after cutting. When less than 200 growing degree days accumulated, there would be little regrowth to use up valuable stored carbohydrates and proteins in the alfalfa roots. This would result in good winter survival of the alfalfa plants.
3.) Fall pasture management:
Most producers want to extend the grazing season as late as possible before entering winter since the weather condition in the fall is suitable to some degree for forage growth. This can sometimes result in overgrazing the pasture, which is not desirable for stand longevity. Therefore, it’s important to leave 6 inches of stubble before entering winter, which will be helpful to catch snow and regrow in early spring. Like fall harvest management of alfalfa, testing soil phosphorus, potassium, and pH will be important to maintain good quality pasture and follow the soil testing recommendations. In particular, if you have a new late summer seeding, leaving the new seeding without grazing will be important. Grazing newly planted pasture can be damaged by trampling and close grazing. Fall is also a good timing to check the status of your pasture to see if your pasture needs to be frost-seeded next spring using red clover. To do this, pastures should be closely grazed or mechanically mowed in the late fall or winter to open stands and expose soil. A chain drag or light disking can also be an option to help open the stand to increase the opportunity for better seed to soil contact.