Forage gap warfare: interseeding into bermudagrass

The author is the extension forage specialist for the University of Arkansas. Paul Beck, Dirk Philipp and Kenny Simon contributed to this article.

In Arkansas and the mid-South, bermudagrass will produce green blade tips in March, but sustained growth does not occur until late April or early May when night temperatures are 60°F or more for about a week. At the end of the growing season, growth declines sharply when night temperatures drop into the 50s, and growth basically stops when night temperatures drop into the 40s. Other points to consider are that bermudagrass is very resilient, it tolerates herbicide suppression, and it is compatible with complementary cool-season forages.

The most common annual forages interseeded into bermudagrass are annual ryegrass, small grains, annual and perennial legumes, and forage brassicas. Ryegrass is highly productive and the growth profile extends into late spring, but it is less productive in fall than small grains or brassicas.

Winter oats are fast growing, palatable and easy to establish, but winterkill can be a problem in the upper South. Rye is fast growing, winterhardy and tolerates poor soil. It is very early maturing with rapid spring growth. Wheat is readily available, more cold tolerant than oats, matures later than rye, but earlier than ryegrass.

All of the small grains have less shading impact on spring greenup of the underlying bermudagrass sod than ryegrass. Mixtures of small grains with ryegrass have been shown to provide a reliable and longer grazing period from fall through spring than small grains or ryegrass alone. Forage brassica in the South is used for fall grazing and has minimal regrowth in spring.

Have a gap plan

Recommendations for filling fall forage gaps with winter annuals in the mid to upper South are as follows. Typical seeding recommendations are to clip or graze the bermudagrass to a 2 to 4-inch stubble, and interseed 100 to 120 pounds of small grain with 20 pounds of annual ryegrass per acre between September 15 and October 15. A simple calendar of estimated grazing periods for different winter annual forage options is illustrated in the figure.

For grazing by November 1 to 15: Small grains and ryegrass intended for grazing by early November must be planted before September 15. Planting on a tilled seedbed or no-tilled into harvested crop fields will be required for this to work. Apply fertilizer nitrogen (N) after the stand comes up to ensure fall growth. Apply phosphorus (P) and potassium (K) according to soil test. Apply more N in February for sustained growth into spring. Due to the tillage requirement, this option will not fit every case or every field. However, selecting specific fields for this early planting option may fill a void until other forage is available.

For grazing by December 1 to 15: Winter annuals intended for grazing in early December can be interseeded into warm-season grass sod or planted in crop fields from September 15 to October 1. Suppress grass sod with a low rate of glyphosate herbicide or with moderate disking when planting this early to prevent competition with the small grain seedlings. Planting can be done with a no-till drill or by disking followed by broadcast of seed and dragging with a harrow. Apply fertilizer N after the stand comes up to ensure growth, add P and K according to soil test, and then broadcast more N in February for sustained growth into spring.

For grazing by February to early March: Planting annuals after mid-October into November will allow good establishment, but forage production will be delayed until February or early March. Fertilizer applications can be delayed until February since growth potential is limited during mid-winter.

How much to plant

Limit grazing of winter annuals is an effective supplement to the increased nutrient requirements of spring calving cowherds. Research at the University of Arkansas has shown that limit-grazed cows on winter annuals two days per week and fed hay the remaining time performed as well as cows on hay with a balanced ration. Plant one-tenth acre per cow per day of the week to be grazed through the winter. For example, if cows will be limit-grazed three days per week, then plant three-tenths of an acre per cow. For 50 cows, that equals 15 acres.

Estimating stocking rate at turn-in is important to prevent overgrazing. At least 900 to 1,200 pounds of forage dry matter per acre should be available before turn-in. Research indicates that 2.5 to 5 pounds of forage dry matter per pound of calf bodyweight allows for average daily gains of 2 to 2.5 pounds on winter annual pasture. This translates to 1,000 to 2,000 pounds of forage dry matter per 400-pound calf. So winter annual pasture with 1,000 pounds per acre of dry matter in the fall could sustain one 400-pound calf per acre. As forage yield increases in spring, stocking rate can increase accordingly.

Legumes can help

Annual legumes such as crimson clover, arrowleaf clover and hairy vetch provide little forage growth after planting in fall but provide excellent quality forage for spring grazing. The spring growth profiles also matched the small grain and ryegrass profiles, meaning that the forage matures in late spring and dies; this allows bermudagrass to grow through summer.

Hairy vetch shaded bermudagrass more than the annual clovers. Perennial legumes such as red and white clover and alfalfa became more competitive through spring and early summer, depending on legume stand density. Consider the important seasonal production of bermudagrass when selecting a cool-season forage due to competitive growth differences in spring and summer.

Brassicas are an option

Forage brassicas are becoming popular in the Southeast for fall grazing. Commonly planted species include forage turnip, rape and turnip/rape hybrids. Early planting is the key to successful brassica establishment. For Arkansas conditions, we have found that planting from late August to September 15 produces good results. Later planting produces very poor yield.

Generally, light to moderate disking of the sod is required for successful establishment. For pure stands, plant 5 pounds per acre of brassica. For mixtures with ryegrass or small grain, plant 2 to 3 pounds per acre of brassica. Our results have shown over 2,000 pounds per acre of dry matter by late October and over 5,000 pounds dry matter by early December in well-managed stands. Forage brassica mixed with ryegrass can provide excellent fall grazing from the brassica and spring grazing from the ryegrass.

Livestock unaccustomed to brassica will often refuse the forage at first turn-in; plan an acclimation period on a small area of brassica pasture. Once the animals have accepted the brassica forage, strip grazing with a single-strand electric wire will prevent trampling and excessive waste of the forage. Turnip bulbs are a secondary feed source and animals learn to consume those as well. Tests indicate bulbs contain about 10 percent crude protein and 78 to 80 percent total digestible nutrients.

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