– Chris Teutsch, UK Research and Education Center at Princeton
Wet conditions this winter have resulted in almost complete disturbance in and around hay feeding areas. Even well-designed hay feeding pads will have significant damage surrounding the pad where animals enter and leave. These highly disturbed areas create perfect growing conditions for summer annual weeds like spiny pigweed and cockle bur. Their growth is stimulated be lack of competition from a healthy and vigorous sod and the high fertility from the concentrated area of dung, urine and rotting hay. The objective of this article is to outline approached for dealing with these areas.
Approach I: Planting cool-season grasses and legumes
The first strategy is to seed cool-season grasses or a mixture of grasses and legumes in the spring. While this commonly done, results are usually less than spectacular in most years. This is due to several reasons. The first is that seedings are normally delayed until late spring or early summer. This does not allow adequate time for the seedlings to develop a large enough root system to sustain them through a hot and often dry summer. The second reason is that summer annual weed pressure is very high. Summer annuals weeds like foxtail, crabgrass (?), goosegrass, spiny pigweed, cockle bur and others actively compete with cool-season seedlings for light and water, often causing stand failures.
If you decide to attempt a spring planting of cool-season grasses and legumes, there are several things that you can do to enhance, but by no means guarantee success. These are listed below.
Plant adapted forage species. Plant forages that are well adapted to Kentucky and the soils and drainage found on your farm. Tall fescue, red clover and ladino clover are by far are best adapted and most versatile forage species for pastures in the Commonwealth. Information on the best varieties to use can be found on the UK Forages webpage.
Consider leaving legumes out of the mix. While legumes are an important part of grassland ecosystems, herbicide options for controlling weeds in grass-legume mixtures are limited. Leaving legumes out will allow you to apply selective herbicides to control broadleaf summer annual weeds.
Use the high end of the seeding rate. Seeding rates are normally given as a range. For spring seedings, make sure and use the high end of this range. Rapid canopy closure is critical to suppressing summer annual weeds.
Plant as early as possible. Spring seeded cool-season forages should be planted starting in early to mid-March. Early plantings will have more time to emerge and form a canopy that can shade summer annuals weeds. They will also have additional time to develop a root system that can sustain the developing seeding during the summer months.
Plant in two directions. If drilling, cut your seeding rate in half and plant in two directions. This will aid in obtaining quicker canopy closure and hopefully prevent and shade summer annual weeds.
Check seeding depth. Small seeded cool-season forages should not be planted deeper than ½ inch. Make sure to check and recheck your seeding depth. Seeding deeper than ½ inch will delay emergence, result in uneven stands, and in many cases cause complete stand failure.
Control broadleaf weeds in cool-season grasses. Once seedling have four collared leaves, some herbicides can be applied. Always consult and follow label directions. For more information on using herbicides on new seedings, contact your local extension agent.
Clip or flash graze new stands. Summer annual weeds compete very aggressively for light, water, and nutrients with cool-season grass seedlings that are trying to establish. If this competition is not controlled, it will likely result in stand failure. The most effective control this competition is to flash graze these paddocks before weeds get to far along. Flash grazing is accomplished be placing a large number of animals in small areas for a short period of time. This reduces selective grazing and increase grazing uniformity.
Approach II: Planting a warm-season annual grasses
The second strategy involves planting a summer annual grass in late spring or early summer and has much higher probability of success. Summer annual grasses, especially sorghum-sudangrass or sudangrass, have very rapid emergence and canopy closure. This will prevent summer annuals weeds from germinating and provide forage for grazing or harvesting during the summer months (Figure 2). Perennial cool-season grasses can then be reseeded under more ideal conditions in late or summer or early fall. If you decide to use summer annuals grasses, there are several things that you can do to enhance your success. These are listed below.
Plant adapted summer annuals species. Always plant forages that are well adapted to Kentucky and the soils and conditions on your farm. Summer annuals that can be used to reclaim hay feeding areas include sudangrass, sorghum-sudangrass, pearl millet, and crabgrass. Detailed information on the adaptability, establishment, and management of these species can be found in UK publication AGR-229.
Use the high end of the seeding rate. Seeding rates are normally given as a range. Make sure and use the high end of this range. Even with summer annuals, rapid canopy closure is critical for reducing summer annual weeds.
Plant after soil warms. For summer annuals grasses to germinate and rapidly emerge, soil temperatures at planting should be at least 60 degrees F. As a general rule, this is about two weeks after the “ideal” corn planting date. This should allow plenty of time to let the area dry out and to get it smoothed up prior to planting. If there is a delay in planting the summer annuals after final tillage, it may be a good idea to do one more pass of light tillage to disturb any weed seedling that may have germinated.
Control broadleaf weeds. Once warm-season annual grasses are established, some herbicides can be applied to control summer annual broadleaf weeds. If you plan to reseed cools-season perennials in the fall, make sure and check the label for reseeding restrictions prior to application. Always consult and follow label directions. For more information on using herbicides on summer annual grasses, contact your local extension agent.
Grazing summer annuals grasses. Allow taller growing summer annuals like sorghum-sudangrass and pearl millet to reach a height of 18-24 inches before grazing and stop grazing a to 8-10 inches. Regrowth can be stimulated be applying 40-60 lb N/A after each grazing, but the last. Crabgrass can be grazed once it reaches a height of 6 to 8 inches. Cattle should be pulled off once it has been grazed to a height of 3 to 4 inches.
Haying summer annual grasses. Allow taller growing to reach a height of 30 to 40 inches before mowing. This will optimize yield and forage quality. If regrowth is desired, do not mow close than 6 inches apply 40 to 60 lb N/A after each cutting, but the last. Crabgrass should be cut for hay at the late boot-stage. Care should be taken to not mow crabgrass closer than 3 to 4 inches.
Reseeding cool-season grasses in the fall. Pastures should be sprayed with a non-selective herbicide in late summer to control any remaining summer annual grass and any weeds that have germinated. Cool-season grasses can be no-tilled into the killed pasture area.