Dr. Michelle Arnold: Grass Tetany: A Complicated Disorder With An Easy Prevention

Chris Teutsch Univerity of Kentucky Grain and Forage Center of Excellence, Princeton, Kentucky

Crabgrass is a weed, right? Yes, if it is in your wife’s flowers, maybe if it is in your hayfield, and probably not if it is in your pasture. I spent seventeen years working in the Southern Piedmont region of Virginia and one valuable lesson that I learned was that if it wasn’t for crabgrass and wiregrass (bermudagrass) we would have a lot of hungry cows during the summer months! Crabgrass is a species often shows up in thin stands of cool season grasses or areas where the stand has been damaged by hay feeding or traffic. Crabgrass is a species of opportunity. It is does not show up in a well-managed cool season stand, but rather where there is an opening in a sod. In fact, a crabgrass plant needs a six-inch opening to get started and be productive. The point

that I want to make is that crabgrass is NOT Figure 1. Volunteer crabgrass stand developing in a grazed out annual ryegrass pasture at UK Research and Education Center at Princeton

Variety Proprietor/Distributor Seeding Vigor1 JUN 9 Percent Stand Maturity2 Yield (tons/acre)

JUN 9 OCT 11 JUL 9 AUG 2 SEP 2 OCT 11 JUL 9 AUG 2 SEP 2 OCT 11 TOTAL

Commercial Varieties-Available for Farm Use

Impact Barenburg USA 4.0 99 99 37.0 46.3 58.0 58.0 1.69 1.62 2.11 1.12 6.54*

Mojo w YJ3 Barenburg USA 3.5 98 98 41.0 53.5 58.0 58.0 1.52 1.75 1.93 0.97 6.16*

RedRiver Noble Foundation 3.5 96 88 45.0 55.5 58.0 58.0 1.65 1.49 1.66 0.68 5.48

QuickNBig Noble Foundation

Experimental Varieties

BARDSIRR Barenburg USA 5.0 100 23 49.3 55.5 58.0 58.0 1.96 1.13 1.14 0.17 4.39

4.1 97 97 41.0 51.8 58.0 58.0 1.45 1.53 2.00 0.88 5.87*

Mean CV,% LSD,0.05 4.0 98 81 42.7 52.5 58.0 58.0 1.65 1.50 1.77 0.76 5.69 12.3 2 13 7.5 4.5 0.0 0.0 9.98 24.53 10.38 17.01 7.72 0.8 3 16 4.9 3.7 0.0 0.0 0.25 0.57 0.28 0.20 0.68

1. Vigor score based on a scale of 1 to 5 with 5 being the most vigorous seedling growth. 2. Maturity rating scale: 37=flag leaf emergence, 45=boot swollen, 50=beginning of inflorescence emergence, 58=complete emergence of inflorescence, 62=beginniing of pollen shed. 3. YJ=yellow jacket coating in the seed. *Not significantly different from the highest numeerical valie in the column, based on the 0.05 LSD. Nitrogen Application: 60 lb/ A of actual nitrogen on May 21 and 40 lb/A on Auguest 3 (Total of 100 lb of N/acre) going to take the world over anytime soon. 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 stands 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 crabgrass stands, whether they are volunteer or an improved variety that was intentionally established. 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. Crabgrass seed can be fluffy causing it to bridge in seeders. To help with this problem, it 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 early spring. One variety of crabgrass comes with a seed coating that makes it flow through seeders better. The downside is that it makes up a substantial portion of the total weight making it necessary to increase the seeding rate, although seed cost per pound tends to be lower. 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. Although nitrogen is a touchy subject this spring, we know that nitrogen fertilizer not only increased dry matter yield, but also the crude protein concentration in crabgrass forage. If you are overseeding hay feeding areas, no additional nitrogen should be applied. 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 to 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. 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. Transitioning Back to Cool Season Perennials Thinning stands containing crabgrass can be transitioned back to cool season perennials by no-tilling well adapted perennials in summer or early fall. Fall plantings avoids competition from crabgrass and other summer annuals grasses and broadleaves in time. The following tips will help you have success with adding perennial species back to thinning stands. Soil test and apply needed P, K, and lime. Soil test to ensure that soil pH is in the range of 6.0 to 6.4 and P and K are in the medium to high range. Closely graze crabgrass pastures. Close grazing suppresses seed formation and removes plant residue from pastures. This helps to ensure proper seed placement and good soil to seed contact when no-tilling. No-till perennial cool season grasses in late summer or early fall. Planting in late summer or early fall avoids competition from summer weeds. Apply nitrogen after cool season grasses have emerged. A small amount of nitrogen, 30-40 lb N/A, applied in the fall will help grasses tiller and prepare them for rapid growth in the spring. Apply nitrogen in mid-March. A spring application of nitrogen will promote cool season grass growth and enhance canopy closure. A solid canopy of well adapted cool season grasses will help keep warm season weeds at bay. Do not graze cool season grasses closely. Leave at least 4-5 inches of residual growth as you move into the summer months. As mentioned above, when we graze cool season grass stands closely, especially as you move into summer, it encourages summer grasses and weeds Do not apply late spring or early summer nitrogen. Applying nitrogen in late spring or early summer tends to encourage summer annual grasses and weeds in pastures. Crabgrass isn’t for everyone, although most everyone has it in their pastures. It is just another resource that could be used to increase the summer productivity of thinning cool season pastures and at the same time take up spaces that may have been occupied be summer annual weeds.

FEATURED PUBLICATION

This month’s featured publication is: “Crabgrass” by Chris Teutsch, Ray Smith, Tom Keene, and Jimmy C. Henning. It can be accessed at http://bit.ly/342CcRK or at your local extension office

FEATURED VIDEO

This month’s featured video is Mowing and

conditioning for bale silage: equipment and harvest

management-Jessica Williams. This presentation was given as part of the 2022 Alfalfa and Stored Forage Conference, Conserving High Quality Forage as Baleage, that was held in Bowling Green, KY on February 24, 2022. This conference was joint effort of the Kentucky Forage and Grassland Council and University of Kentucky Cooperative Extension. Proceedings of this conference are available at https://uknowledge.uky.edu/ ky_alfalfa/2022/.

FENCING TIP

Properly build fence brace assemblies. Regardless of the type of fence that you are putting up, the brace assembly is the heart of the fencing system. The most recommended brace assembly for our region is the H-brace. The brace post and corner post should be a CCA treated post that is 6-8 inches in diameter and 8 feet in length and should be driven small end down. The brace rail should be a CCA treated post that is 5 inches in diameter and 10 feet in length. The brace rail should be pinned with ½ inch Class III Galvanized pins that are 4 and 10 inches in length. The brace wire should be two wraps of a 170,000 psi Class III Galvanized high tensile wire that is tightened with a heavy duty in-line ratcheting strainer. After tensioning, the brace wires should be pulled together by loosely wrapping piece of high tensile wire on each side of the strainer and pushing the wraps toward the post. To learn how to properly build a brace, make planes for attend the Kentucky fencing school this fall.

FORAGE MANAGEMENT TIPS

Seed warm season annual grasses once soil temperature reaches 60 F. Clip, graze or make hay to prevent seedhead formation in cool season pastures. Rotate cool season pastures when residual is 3-4 inches. Consider temporary electric fencing to sub-divide larger pastures and exclude areas for mechanical harvesting. Scout pastures for summer annual weeds and control when small. Make plans to attend summer forage tours and fencing schools in the fall.