Seed Treatments Improve Germination Rates, Crop Health
By Bill Mahanna and Ev Thomas
Considerable changes in seed treatments have occurred in the past decade, both in the extent of use and in the type of treatments. These changes have been very much for the better, particularly regarding seed corn treatments but with forage seeds, as well. Not only is a much higher percentage of forage seeds coated or otherwise treated with some material, but there's a wide range of treatment options. The following is a summary of some of the more significant changes in seed treatments that impact the dairy industry.
Evolving Seed Corn Treatments
Until about 10 years ago, planterbox seed corn treatments were the standard. These “three-way” treatments were farmer-applied and combined two insecticides (usually diazinon and lindane) and the fungicide captan. The recommendation was to thoroughly mix the powdered treatment with the seed, but far too often the envelope of seed treatment was dumped into the already filled seed hopper and stirred a bit, if at all.
It was sometimes possible to detect the mixing process employed by looking at the farmer’s right arm: “Pink arm” up to the elbow (due to the seed treatment coloring) was an indication of improper mixing technique! And while we’d like to believe that farmers always used these treatments, the occasional corn emergence disaster (and subsequent admission of guilt by the farmer) was testament to the fact that they did not.
Planterbox treatments were better suited for the plate-type planters; the type that farmers with some gray hair may remember. A 16-cell or 24-cell plate was located at the bottom of the seed unit, and even a carelessly applied seed treatment eventually found its way by gravity to the bottom of the unit and was somewhat effective.
But planterbox treatments are not the ideal match for today’s modern finger pickup and air planters. The new seed corn treatments, applied by the seed company and consisting of at least one fungicide and an insecticide, eliminate the “pink arm” problem for the farmer. Although properly applied planterbox treatments often performed well in university trials, the use of treated seed means one less chore for the farmer to do, and there are a number of formulations and concentrations of treatments to suit a variety of field and pest conditions.
The two most common seed corn treatments are Poncho® and Cruiser Extreme®, each of which is available in at least two rates. The lower rate is used for seedling insects such as seed corn maggots and seed-borne diseases, while the higher rate is used for the control of seedling pests as well as providing some protection against corn rootworms. (Opinions vary as to the extent of rootworm control afforded by seed treatment, with some entomologists suggesting that even the highest rate may not be adequate under heavy rootworm pressure.)
In the past year or two, a seed treatment that’s also labeled for nematode control has become available from some seed companies.
NEW SEED CORN TREATMENTS applied by the seed corn company, as opposed to planter box treatments, are quite effective. They also result in one less chore for busy farmers.
Began with Forage Seeds
Seed coatings for small-seeded forages, particularly legumes such as alfalfa and red clover, have been around for a long time. It’s been over a generation since farmers have had to apply rhizobial inoculants to alfalfa and clover, since the seed of almost all these species is now preinoculated. A rhizobial seed coating helps provide an ideal microenvironment for effective nodulation. Many of the preinoculated legume seeds also include metalaxyl, a fungicide that helps prevent early season fungal blights.
Forage seed coatings include limestone, gypsum, and polymers. Some are used to better adhere the inoculant to the seed, while others are intended to supply nutrients and to boost the weight of the seed to improve seed-to-soil contact. When materials are added to enhance the size or weight, the process is often termed “pelleting.” This is much more common with certain grass species than with forage legume seed.
For instance: teff is an annual forage grass with a tiny seed, about 1.3 million seeds per pound. This makes proper seeder calibration difficult which is why much of the teff seed sold in the U.S. is coated, in effect, doubling its size. However, heavy seed coatings reduce the number of seeds per pound. You need to take this into consideration when calculating seeding rates.
Recent grass seeding trials by Cornell University included coated and uncoated comparisons of varieties of orchardgrass and tall fescue. The seed coatings didn’t adversely impact yields, and while there was a slight trend to higher yield, in most cases the yield differences weren't significant.
Many Options Exist
A wide variety of products can be included in seed coatings; some pasture grass seed is coated with a fertilizer containing the major nutrients plus several secondary and micronutrients. One of the newer seed coatings on the market is a water-absorbing polymer. This coating is designed to retain water that would normally be lost through evaporation and then release it back to the seed as needed. The goal is enhancing germination and growth under moderately dry conditions.
In the future, we can look forward to new seed treatments, both nutritive and nonnutritive, to improve the chances of successful forage stands.
Originally published in the March 2012 Field to Feedbunk issue. Reproduced with permission.