Farming Magazine - April, 2012
Forages: Spring Planting Thoughts
They say that timing is everything. While this may be an exaggeration, it's not much of one when it comes to spring planting. The difference between seeding alfalfa or oats in April versus May can be the difference between a good crop and a poor one, just as May-planted corn is almost always higher yielding than the same corn hybrid planted in June. But don't let the rush of spring planting cause you to become careless. Details, even the seemingly small ones, can make a big difference!
Forage crop seeding rate and seedbed preparation
It's easy to find seeding rate recommendations for alfalfa and other small-seeded forage crops; most suggest a rate between 15 and 20 pounds of seed per acre (legume or legume and grass seed combined). At these rates, how many seeds are you actually planting? Alfalfa contains about 200,000 seeds per pound, so a seeding rate of 18 pounds per acre - a common recommendation when alfalfa is seeded without a grass companion crop - is over 80 seeds per square foot. We consider an ideal stand of alfalfa in the first full production year to be 12 plants per square foot; therefore, to achieve a full stand all you need is for one seed in six to germinate and survive. Timothy contains 1.2 million seeds per pound; at a seeding rate of 8 pounds per acre - some sources suggest 10 pounds - that's 220 seeds per square foot. It's tough to find information on what's considered a "full stand" of timothy, but it's surely a lot less than 220 plants per square foot!
The reason forage seeding rates are so high is because small seeds need to be planted shallowly: For both alfalfa and timothy, no more than .25 to .5 inch deep. That's why field preparation is so important; a cloddy, loose seedbed can result in forage seeds being buried an inch or more deep, resulting in a poor survival rate. With seeding this shallow you can often find some forage seeds lying on the soil surface. Seed cost is usually such a small part of the total investment in forage establishment that we shoot high in seeding rates just to be safe. However, good seedbed preparation can result in quicker germination, a thicker initial stand, and therefore better competition to broadleaf weeds and annual grasses. While a dense first-year alfalfa stand will typically lose a high percentage of plants during the first winter, research has shown higher seeding year yields with high-density stands.
Good seedbed preparation results in a well-granulated soil with few clods. No-till drills can produce just such a seedbed - albeit in a narrow strip - as long as soil moisture is appropriate and the equipment is properly adjusted. At Miner Institute we've produced excellent stands of alfalfa grass using reduced (and occasionally zero) tillage. One of the essential parts of a no-till drill is the firming or packing wheels located directly behind the seed tubes. Excessive tillage (resulting in an overly fluffy seedbed) is never a problem with no-till. With conventional tillage, though, some farmers apparently believe that a third or fourth disking is necessary, while in reality they're often doing more harm than good. A common mistake is for a farmer to seed into a very fluffy seedbed, then compact the soil by the use of press wheels on the grain drill or by using a roller or cultipacker. These are all good implements, but what's important is to have a level, firm seedbed at the time of seeding. This often means rolling or cultipacking before seeding, even if the drill is equipped with press wheels. Two rules of thumb that may be useful: Prior to seeding, the field should be firm enough that if you walk across it the soil won't come over the top of the soles of your shoes or work boots. Leaving a footprint .75 inch or deeper is an indication that more firming is needed. Another rule of thumb is that an empty pickup truck will make an impression in the field no deeper than about 1 inch. That's why Miner Institute cultipacks conventionally tilled fields before seeding, and then uses a press-wheel drill so the soil over the seed is firmed twice: once just before and once just after seeding. The Institute has only had one seeding failure in the past 30 years: reed canarygrass seeded a bit too late in the spring. The canarygrass germinated and grew, but the annual grasses grew even faster and choked it out. Reed canarygrass is a notoriously weak, slow-growing seedling, and that was the first, and last, time we seeded canarygrass without a companion forage. (I seldom recommend this species any longer since tall fescue is higher yielding with better forage quality and good tolerance to variable drainage conditions.)
Corn planting rates
Compared to forage seeds, corn is a large seed that even though planted about 2 inches deep has a high percentage of seedling emergence. Even though the tag on the seed corn bag may state germination to be 95 percent, in reality it's often 98 percent or greater. Therefore, unless seedling blights or early-season insect pests such as seed corn maggots wreak havoc, it's common to wind up with at least 90 percent of planted seeds maturing into harvestable plants. Seed treatments applied by the seed company instead of by the farmer (or in some cases not at all) are resulting in more consistent stands, as are our modern corn planters. In the old days we used to overplant by 15 percent, so if we wanted to wind up with, for instance, 24,000 corn plants per acre, we'd plant 27,000 to 28,000 seeds. Now we usually aim much higher for population, at least 30,000 plants per acre for corn silage and often 32,000 to 33,000. Most sources recommend overplanting by 10 percent, and a few suggest overplanting by only 5 percent. (Iowa State University research has found that only 4 to 7 percent of seeds fail to produce a plant.) However, I'm not ready to go quite that far yet, especially with no-till and or early planting. The earlier you plant, the more I'd suggest that you stick to the 10 percent overplanting guideline. No-till planting into cold soils? Consider overplanting by 15 percent, since in most cases you have more to lose from undershooting on corn plant population. At $250 per 80,000 kernel unit of seed, increasing your planting rate by 5 percent only amounts to a few more dollars per acre. Don't leave some yield potential in the seed bag.
Ev Thomas has worked as an agronomist in New York for 45 years, first with Cornell University Cooperative Extension, then with the William H. Miner Agricultural Research Institute in Chazy, N.Y., including managing its 680-acre crop operation. He continues to work part-time for Miner Institute and is now an agronomist at Oak Point Agronomics. He has a written our Forage column for over 13 years and has been an expert contributor on a number of other topics.