Fall Pasture and Grazing Management

submitted by David Tuggle

Be careful not to hurt your pasture stand this fall. Read about tips for successful fall pasture management. 
Fall pasture growth often provides additional opportunity for grazing livestock; however, careful management of pastures is essential for the over-wintering of forages and improvement into the next growing season. A dry end to our summer has stunted fall pasture regrowth dramatically, but as rains begin to increase in frequency in most regions, fall grazing is beginning to look a little more promising, but could be detrimental to your forage stand if not managed carefully.

During the fall, perennial pasture forages are experiencing the development of new shoots – which gives us the accumulated forage to graze – as well as root regeneration. During the period of root regeneration, carbohydrates are being stored as an essential part of the root rebuilding process, which provides the necessary stores for proper over-wintering.These carbohydrates are stored within the crown and roots of the plant, which is generally in the lower 3-4 inches of the plant in cool season perennial pastures, so it is critical that pastures are never grazed below a 3-4 inch stubble height at any point in the season, but especially during the fall. It is often recommended to leave a higher stubble height – often 4-5” – in the fall to give pastures a chance to store those carbohydrates that will give them a “jump start” the following spring. If plants are grazed below the growing point, nutrient stores will be depleted and the “protection” from stress will be dramatically reduced. Overgrazing during the fall inhibits regeneration of the root system and the development of new shoots for the next season’s growth. Implementing a rotational or strip grazing system can help to manage grazing height by reducing paddock size and increasing the ability to monitor plant residue height.

Early fall is a great time to apply nutrients such as lime, potassium, and phosphorus, as this aids in root regeneration and regrowth. Soil tests should be completed, and if pH is below the recommended level for the targeted forage species within that pasture, liming at the recommended rate to improve soil neutrality will help with forage growth and competitiveness with weeds. If moisture is available, pastures will respond to a fall nitrogen application and lower rates of fall-applied nitrogen will not negatively affect legume population within pastures. However, pasture plants’ response to nitrogen is directly correlated with the amount of moisture available, fertilizer application date, and rate of application. It is generally recommended that for cool season mixed species pastures, no more than 40 lb of nitrogen per acre should be applied in the fall of the year.; High rates of nitrogen application could lead to winter kill. If a fall application of fertilizer is desired, no later than an October 1 application date is generally recommended, so now is the time!

Frost and Freezes Increase Cyanide Poisoning Risk 

Cyanide poisoning, more commonly referred to as prussic acid poisoning, can have a very abrupt and deadly effect on ruminant livestock grazing forages and requires careful management as frosts and freezes begin in the area. Plants, such as sorghum, sudangrass, sorghum-sudan hybrids, Johnsongrass, wild cherry, and others, contain compounds that produce free cyanide when these plants are damaged by frost or drought conditions. Grazing these plants when they are producing young shoots (less than 18 inches tall) also increases the risk. Using caution when grazing these forages during times of stress can usually eliminate the possibility of cyanide poisoning in livestock. Waiting for two weeks after a light frost (temperature greater than 28°F) is recommended. For a killing frost, wait until the material is completely dry and brown (usually cyanide dissipates within 72 hours). Grazing at night when a frost is likely is not recommended as high levels of cyanide are produced within hours after frost occurs. Delay feeding silage for six to eight weeks following ensiling of forages in the sorghum family. If cut for hay, allow to dry completely so the cyanide will volatilize prior to baling.