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Coatings for Corn Seeds

March 22, 2002
The Landec Company, which owns the Fielders Choice seed company in Indiana, is again promoting polymer coating of corn seed for very early planting. This is a special polymer, with the ability to "sense" temperature and to become permeable to water only when the temperature reaches a certain point. In the field, this is supposed to act by preventing water uptake by the seed when the soils are too cool for germination anyway, and then to allow water movement into the seed to initiate germination when the soil temperatures are warm. The company is promoting the use of this coating for plantings made much earlier than is normally considered "safe," with the idea that planting can start earlier in this way.

We do not have very much research data on this product. In a trial planted in early May in 1999, the coating resulted in full stands, but delayed emergence of seed in a variable manner, spreading emergence over about 10 days rather than the normal 2 to 3 days. While coated seed produced good stands, the unevenness of these stands took a toll on yield. It may be that the coatings have been changed somewhat since then, such that emergence might be more uniform and faster under warm soil conditions. But it is also clear that nonuniformity of emergence can seriously affect yield, and so should be avoided as much as possible. Observations on coated corn seed planted in 2000 were that the coating again spread out emergence, regardless of the time of planting.

Dr. Tony Vyn at Purdue has been testing this technology, and he found in 2001 that a frost that seriously damaged a stand from uncoated seed planted in early April had little effect on a stand that emerged later due to seed coating. Most of the farmer testimonials used to promote this product have tended to focus on the safety aspect--being able to plant very early (March or early April) and not having to worry about "premature" emergence and subsequent damage.

While we take a neutral view of this technology at this point, pending more research results, we would urge some caution in using coated seed on large acreages. While this material clearly can reduce damage to early-emerging stands, hence providing some "replant insurance," it is likely that the coating will often spread the time of emergence, and we think that this may reduce yields. The question probably comes down to a personal risk approach: do you accept known risks of very early planting and occasional replanting, or do you spend money for seed coating to reduce the replanting risk to some extent, while perhaps increasing risks of nonuniform emergence? It may be best to take the cautious approach of using some coated seed, preferably in half of the planter, with uncoated seed in the other half, and on relatively small areas, until we know more.

There has not been excessive replanting in most areas in the past 3 years, and replant seed policies of companies have meant fairly modest replanting costs. Furthermore, the need to replant tends to be "event-related," depending more on weather events right after planting than on time of planting itself. Finally, up to now at least, using coated seed has restricted hybrid choice to those sold by, or coated by, this company.--Emerson Nafziger

Author: Emerson Nafziger

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