Rock and Roll Agronomy

How Early Can We Start Planting Soybeans in 2008?

by Jason Hanson, Certified Crop Advisor
jlhanson@landolakes.com

Prices of commodities are getting everybody excited to push the yield envelope to squeeze out that last half a bushel or hundred weight of whatever crop and maybe a little more for this next year. And what does everybody say… plant early. That means cereals, corn, canola, beets etc. Depending on your crop mix, some acres are not going to get planted “early” due to weather and how much you can plant will depend on your time zone.

Generally crops like sunflowers, dry beans and soybeans get planted a little later. But more and more growers are moving up their planting dates. That isn’t always the best thing to do, but we won’t find that out until the season is almost over or at harvest. Last year the snow in the northern part of North Dakota had a dramatic affect on canola yields and the May/June rains also affected earlier planted sunflowers as compared to later planted ones, due to disease and stress.

If you go to a meeting or read materials in different farm publication, you will hear where early planting will more often than not have more yield. Most universities will show that earlier growth produces more leaf area, root mass, nodules and eventually yield. So what are some of the things to be mindful when the cereals are planted and the bean seed is staring you in the face? Price of diesel is cheaper today than it will be tomorrow, so why not plant? The spouse wants to go backpacking in Denali at end of June and you could beat the spray season if we could just pull the trigger… right? Above is one data chart showing yield based on planting dates.

Table 4-7. Effect of Planting Date on Yield, Plant Height and Maturity

Planting Date Yield (bu/ac) Plant Height (cm) Days to Maturity May 10 54 109 137 May 24 48 112 125 June 3 47 112 119 June 13 44 93 112 Source: Ablett, Ridgetown College, University of Guelph, 1980-81

This chart is classic of a yield response to most situations with early planting. You can find the same data out of other soybean producing areas in the country. Go Big. Go Early. A few obstacles we run across in this part of the world is that we have to contend with frost in the spring and if our soil temperatures are close to 50 degrees F. So I did a little digging and found that the last average spring frost date varies quite a bit across North Dakota and Minnesota. In the Red River Valley up to about Grand Forks, the date is around April 30. Most of the rest of the state is the May 5-7 time frame and the northern tier areas end up around May 10-12. Since the growing point on beans is above the soil surface, a killing frost getting down to 28 degrees F. would not be a good thing. Using NDAWN to look at the whole station coverage area for when those soil temperature get above 50 degrees varies by area and year. In 2005, the average soil temp hitting a consistent 50 degrees F. occurred in the May 16-19 time frame. For 2006, those dates were May 13-17 and for 2007, it was May 5. Global warming I guess. But that is what we mostly remember is last year. NDSU will state in their soybean production manual that a May 10-25 time frame is the highest yield situation taking into account frost, cool soils, emergence and vigor. Another good study out of the University of Minnesota in Crookston showed that in 2006, a mid-May planting brought the highest yield.

I also know that when you get into the early side of planting soybeans you have to pay attention to the conditions you plant into. In our plots, almost always, treated soybeans emerge faster and end up with more plants per acre. Not always do they yield better as beans can compensate very well depending on the season, but we don’t lose many plants to diseases like pythium and rhizoctonia. If that ground is also wet, you can’t make up for seed that is smeared in and you put a layer of restricted root growth around it by your seed equipment. If it dries out later on, it is not going to be real pretty.

Overall, this year’s soybean seed quality will be an issue. For this northern area we are fortunate that our seed stock is in better shape than most other places. Some areas of the country got wet during harvest and ended up with disease in/on the seed that will affect germination. Same with areas that had drought with splits and cracks in dry climates. I would still pay attention to germination on the seed tag and be mindful of vigor also. Handle seed with care even if you have a great variety with near perfect germination.

Hanson is a certified crop advisor, and rocks and rolls near Devils Lake, N.D. as a regional agronomist with Agriliance/Croplan Genetics.

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Planting Tips

1. Don’t plant unless the soil is dry enough to support equipment. Shallow soil compaction will haunt you the remainder of the growing season.
2. Soil temperatures of the seed bed should be at minimum 46-48 F or warmer if at all possible. A chilling injury can occur to germinating soybean seed if soil temperatures are below 44 F. This can result in poor seedling vigor and reduced plant population.
3. Plant seed that has been treated with a fungicide if planting into cool soils and if no-till seeding.
4. Plant high quality seed that was grown in 2006. Don’t use old seed!!
   Till the field or clear the residue away from the row to allow the soil to warm up faster and reduce the likelihood of frost damage.
5. With the recent rains in some areas, don’t plant if the fields and soils are on the wet side. Soybean mudded in too soon will fail to establish good plant stands and may result in reduced yield potential.

 By Russ Severson, County Extension Educator, Polk & Red Lake County