I hope your winter pasture is up and running, or soon will be. Two of the most frequently asked questions this time of year are, When is the pasture ready to graze? and, How many animals will it support?
Think of your pasture as a large factory with many workers (plants). If your workers are suppressed (grazed too early) shortly after starting the job (germinating), they will probably never express their full potential. They need time to grow and mature before reaching maximum productivity and being grazed. The amount of vegetation above and below the ground is directly related to a plant's ability to grow and, after being grazed, regrow. Initiate fall grazing when the plants are 8 to 10 inches tall, have become well tillered, and have a well-developed root system that firmly anchors them. If plants are grazed too early, they'll never reach their full growth potential.
How many animals will your pasture support? Most winter pasture growth for fall grazing (November 1 through March 1) occurs by December 15. Our region is typically too cold during January and February for significant pasture growth, which means you must plan to leave enough pasture for grazing to carry the cattle through February. We refer to this method as stockpiling, which is used during months when forage doesn't grow. As a rule, you can stock 400 to 600 pounds of beef per acre in the fall if 8 to 12 inches of forage is available when grazing is initiated. In other words, stock approximately 67 pounds of beef per acre-inch of forage during the first two weeks in November. However, you should subtract 3 inches from the total height because a pasture should not be grazed below a 3-inch stubble height. If it is, regrowth opportunity will be drastically suppressed. For example, let's say you have 10 inches of forage the first week in November:
10 inches 3 inches (reserve) = 7 inches
7 inches x 67 lb. of beef/acre-inch = 469 lb. of beef/acre
(average for the season)
This amount should give your stockers forage through late February.
But what if you must acquire the cattle before your pasture develops? First, draw on your management practices and personal experiences. In a year with average temperature and rainfall, we can expect to grow about 700 pounds for each acre of winter pasture in the fall. With adequate fertility (proper pH and sufficient phosphorus and potassium), we can expect 13 pounds of additional forage (dry matter) per pound of actual nitrogen applied in the fall. If the nitrogen were applied at 80 pounds of actual nitrogen per acre, you would need to use the following:
235 lb. of ammonium nitrate (34-0-0)/acre or 174 lb. of urea (46-0-0)/acre or 98 lb. of anhydrous ammonia (82-0-0)/acre
Given this information, what will be the estimated stocking rate per acre?
(700 lb. of dry-matter forage/acre) + (80 lb. of N x 13 lb. of forage/lb. of N)
= (700 lb. of dry-matter forage/acre) + 1,040
100 days' grazing (November 15March 1) = 17.4 lb. of dry-matter forage available/day
Other factors to consider when winter pasture is grazed are removing cattle or grazing more solid areas during periods of excessive rainfall, removing cattle entirely during periods of ice or snow, and having enough reserve feed to maintain stock physiology when cattle are not on pasture.