Part 5: When Do I Plant and How Much Seed Do I Use?
In the earlier posts in this series, I discussed some of the decisions and planning that need to be taken ahead of planting hay and pasture fields. For this article, we have entered the ideal planting time for forage grasses and legumes. However although we are in the ideal window for planting, there will be areas that have received enough rainfall to recharge the topsoil with moisture as well as areas that have not received enough rainfall for a successful seeding. For those areas that remain dry until mid- to late-October, the best decision is likely to postpone planting until next year.
Some species have specific requirements that limit how late in the fall you can plant. For example, reed canarygrass requires at least six weeks between planting and the average date of the first frost; otherwise, the crop could be winterkilled or severely weakened over the winter leaving the crop unable to compete with the usual spring flush of weeds. Other species, such as Kentucky bluegrass, just take a very long time (21 to 28 days) to germinate and should not be planted late in the fall. Before deciding to plant a species or mixture, be sure to study the species in question to avoid missing the ideal planting window.
In areas that have received enough rainfall to replace soil moisture reserves, planting can begin. Early planting can lead to well established forage seedlings that are able to survive winter temperature extremes and get off to an early vigorous start next spring. Early planted stands are better at competing against weeds next spring and often produce higher yields as well. Work by Dr. Marvin Hall at the Pennsylvania State University showed significant yield decreases for all forage species tested as the date of fall planting was delayed with higher losses occurring the further north the site was located.
If planting into a prepared or tilled seedbed, be sure that all weeds have been killed during soil preparation and that a good smooth (clod-free), firm (your shoe should not sink deeper than the sole level) seedbed is prepared for planting. Seed is then broadcast on the seedbed and firmed or pressed into the soil with any number of devices. Seed of small seeded forages should not be buried more than 1/8 to ¼ inch deep. Covering the seed is ideal since seed in contact with moist soil readily absorbs water but is not quickly dried again by the heat from the sun. Seed can also be planted using a Brillion seeder followed by a cultipacker or roller or seed can be placed in the soil using a drill with packing wheels that firm soil over the seed.
Since drills (no-till and conventional drills) place the seed in rows from 4 to 8 inches apart, depending on the drill, I generally recommend that you drill at half the recommended seeding rate and run the drill twice over the field at about a 45 degree angle. This will help new seedlings to cover the soil surface more quickly and reduce the chances for weed seed to germinate and compete with the new forage crop.
Another method of seeding is to use a no-till drill following an herbicide burn-down program. This is especially useful when perennial weeds with underground rhizome systems are present. Examples of these weeds are hemp dogbane, Canada thistle, and horsenettle. Often several herbicide applications will be needed to get these weeds under control so plan a weed control program well ahead of seeding. One of the best times to apply a translocated herbicide is in fall when weeds are sending carbohydrates (sugars) down to underground storage organs (rhizomes). If a systemic herbicide that can move inside the plant is used, it will be taken with the sugars down to the rhizomes and help kill the meristem buds that are next year’s growing sites for the weed. Read the herbicide label for the exact interval between treatment and seeding. Generally for Roundup® or glyphosate you should wait several weeks after herbicide application before planting. Since the herbicides used for control of these perennial broadleaf weeds will kill legumes that often are included as a component of pasture mixtures, it is best to work on controlling these weeds a year or two before spending the money to establish a new seeding or to renovate an existing stand.
In all cases I’ve talked about, be certain to calibrate your seeding equipment and make sure the drills and other equipment are clean and functional before entering the field. These days forage seed is quite expensive so make the most of the money you spend by accurately calibrating your equipment. This involves the following procedure: weigh out some seed to add to the planting equipment, determine the width of area covered with seed by the equipment (in feet), run it for a certain number of feet (the length—say 50 or 100 feet); multiplying the two numbers together to get the number of square feet covered by the seed; divide that number by 43,560 (number of square feet in one acre); and finally weigh the amount of seed remaining in the equipment. Subtract the final weight from initial weight and divide that number by the number of acres you covered (usually this will be a number such as 0.15 or even 0.015 or other very small number). If your seed weights were in pounds of seed then the number you calculate at the end will be in pounds per acre or if you had access to an egg scale or something that measures in grams then divide the number of grams of seed used by 454 (grams per pound) to obtain pounds of seed and then divide that number by the number of acres planted in the calibration test. If all else fails, email me or give me a call and I’ll help you do the calculations.
In summary, I’ll list some of the key points to keep in mind.
- Make adjustments to soil fertility well in advance of seeding or renovating.
- Have all perennial weeds under control before establishing a new seeding or conducting a major renovation in a field.
- Monitor soil moisture levels to be sure an adequate reserve of soil water is available to establish the crop.
- Understand the requirements for the forage specie or species chosen especially as it relates to fall planting date.
- Start with a weed-free seedbed whether for conventional tillage or no-till.
- Unless the site is known to be very low in available soil nitrogen (N), allow the new seedlings to develop 2 to 3 leaves before applying N in the fall.
- Don’t delay planting; try to hit the optimum planting window.
- Ideally, cover the seed with just a little soil but at the very least press the seed into the soil to ensure good soil to seed contact.
- Most seeding rates really refer to the numbers of pure live seed (viable potential seedlings) that should be planted per acre so do the proper calculations to plant the correct amount especially when using coated seed.
- If using preinoculated, lime-coated legume seed as a component of the pasture/hay mix, you should check to be certain the seed has been stored away from heat and high humidity and is not more than a year old, otherwise fresh legume inoculant should be applied to the seed just prior to planting.
- Many small seeded species now come with a range of coatings (lime, moisture control compounds, etc.) that can halve the weight of pure live seed in the container so you should be sure to account for this when calculating the correct seeding rate.
In the last installment of this series, I’ll discuss how to manage new pasture and hay fields for long-term healthy stands.
This article was submitted by Dr. Richard Taylor, Extension Agronomist, University of Delaware. Dr. Taylor can be reached at email@example.com