– Chris Teutsch, UK Research and Education Center at Princeton
Crabgrass is a summer annual grass that often shows up in pastures, especially in thin stands that have been damaged by hay feeding or overgrazing. To flourish in a pasture, crabgrass needs a six-inch opening. This means if you have a strong and vigorous sod, crabgrass will be difficult to establish and maintain.
When cool-season pastures are grazed closely and often during the summer months, the composition of these stands tend to shift toward crabgrass. Unfortunately, these volunteer stand of crabgrass are often not managed to their full potential. The objective of this article is to give you a few pointers that will help you get the most out of volunteer crabgrass stands.
Not all crabgrass is created equal. We tend to lump all crabgrass into one category, but there are several species and even improved varieties. Some crabgrass species and even local ecotypes are more productive than others and respond better to improved management. If you want to ensure that you have the most productive crabgrass species, then consider overseeding your volunteer stands with an improved variety of crabgrass (Table 1). More data on crabgrass varieties can be found by clicking on the “Variety Trial” icon found on the UK Forages webpage.
Mix crabgrass with a carrier. Uncoated crabgrass seed can bridge in drills and seeders so the seed can be mixed a carrier, like pelleted limestone or even some red clover and annual lespedeza seed and broadcast onto closely grazed pastures in late winter or spring. The crabgrass seed will begin to germinate in early to mid-May as soil temperatures start to rise. Although crabgrass seed seems expensive, relatively low seeding rates are used. For overseeding pastures, 3-4 lb/A of uncoated seed or 4-6 lb/A of coated seed should be used.
Drag closely grazed pastures to stimulate crabgrass stands. Dragging closely grazed pastures helps to get volunteer seed from the previous season or seed that you have broadcast onto the pasture into contact with soil. Good soil to seed contact is essential for germination and emergence. Any tillage or dragging should be shallow since crabgrass is a very small seed and should be covered no deeper than ¼ inch.
Apply 60-80 lb N/A to volunteer stands. Research conducted in Virginia found that like other summer annual grasses, crabgrass responds well to nitrogen fertilization (Figure 1). Nitrogen fertilizer not only increased dry matter yield, but also the crude protein concentration in crabgrass forage (Figure 2).
Control broadleaf weeds. Once crabgrass seedlings have 3 to 4 collared leaves, then light applications of 2,4-D can be applied to control broadleaf weeds that have germinated. These may include spiny pigweed and cocklebur. Make sure and always following instructions on the herbicide label.
Allow crabgrass to reach a height of 6-8 inches before grazing. Allowing crabgrass to become well established before grazing will increase season long productivity.
Stop grazing at 3-4 inches. By leaving residual leaf area, the regrowth of crabgrass will be more rapid and overall productivity will be increased. Crabgrass pastures can be grazed again once they reach a height of 6-8 inches.
Apply 30-40 lb N/A in mid-summer. If you are getting plenty of rain, you might consider applying a small amount of nitrogen in mid-summer. This will increase late summer growth and improve crude protein levels.
Table 1. Crabgrass performance at UK Research and Education Center at Princeton in 2020. The complete report can be found on the UK Forages webpage.
Allow stands to go to seed at least once during the growing season. Crabgrass is a summer annual grass that behaves like a perennial through prolific reseeding. This means that it must come back from seed each year. Therefore, allowing it goes to seed ensures that there will be plenty of volunteer seed for next year.
Plant a winter annual in late summer or early fall. Crabgrass is productive from June until September. Planting a winter annual grass like annual ryegrass or a small grain can provide late fall or early spring grazing. As these winter annuals are grazed out, crabgrass will germinate and fill in.
OR
Thicken stands up in the fall by interseeding cool-season perennial grasses. If you want to get more cool-season perennial grasses in the pasture, interseeding the pastures in the fall is the best option. This avoids competition from crabgrass and other summer annuals grasses and broadleaves. This interseeding is best accomplished using a no-till drill.
I realize that crabgrass isn’t for everyone, although most everyone has it in their pastures. It is just another resource that you might be able to use to make it through those hot and humid summer months!