Monday, March 17, 2014

Agronomy College

Amid all the talk about precision farming there is one old aspect of precision that we must remember.  That is planting depth.  With snow still on the ground there is increasing chatter about the cold late spring that looms ahead.  A lot can change in a month.  By late April this prediction may turn out to be one more useless bit of information.  However, it is a distinct possibility that when we go out to plant corn this spring we may face cold soil temperatures.  There is a tendency among farmers to shallow up planting depth in response to cold soil conditions.  It is logical to assume that by planting shallow we can encourage the plants to emerge quicker which has indeed been documented by some research.  Faster emergence reduces the risk of seeds laying too long in a cold damp environment which, the thinking goes, will reduce final stand and increase the odds of uneven emergence with more runt plants.

When corn planted 1.5-2 inches deep as shown by the two plants on the left, the nodal roots develop at .75 inches below the soil surface.  Corn planted at less than 1 inch causes the nodal root system to develop closer to the soil surface.  As soils shrink and dry out the shallow root system often has difficulty becoming established.  The struggling small plant trying to get it's roots established often becomes a runt plant.  Instead of faster emergence being a plus, it becomes a negative.  Runt plants do not contribute significantly to yield and can cause reduced yield in neighbouring plants because they compete for sunshine and nutrients.  In my experience, growers make many more mistakes planting corn too shallow than planting corn too deep.

As published in the 2014 Pioneer Agronomy Science Research Summary, Dr Peter Thomison at Ohio State conducted planting depth trials comparing corn planted at .5 inches, 1.5 inches and 3 inches deep.  This work was done at 20 location over two years.

As you may recall the 2011 planting season started with a cold April.  May continued wet and cooler than normal.  The 2011 corn planting season dragged from mid-April to late May.  2012 was the year a few daring souls tried planting corn in March and 90% of the corn was planted by May 1.  Soil temperatures were not a problem.  Later season drought was the problem in 2012.

In both years the yield penalty to shallow planting was significant.  This was especially true in the drought prone season of 2012. 

I have some pictures taken in 2011 at some planting depth side-by-sides conducted here in Ontario that would back up this research.

The chances of reduced stands are greater with the shallow planting than a normal 1.5 inch planting depth.  If you believe anyone who plants corn at .5 inches deep is an idiot, agronomists will remind you that there are lots of idiots every spring.  It is true nobody starts out to plant corn that shallow, but mistakes happen.

When checking for seed depth keep the following in mind.
1. Make sure to move the very loose soil at the top of the planter ridge before making a measurement.  That loose soil at the surface will settle with the first rain.  What may appear to be 1.5" seed depth becomes 1". 
2. Check every row to verify all rows are planting the same depth.
3. Take your measurement at the worst possible spot in the field which in our area is typically the exposed clay knolls.  Make sure corn is at least 1.5 inches in these spots.  Don't worry about corn planted too deep in the loamier areas.  If it happens to go 2-3 inches in those spots won't matter, but corn planted too shallow on the knolls will matter. 
Speaking of new technology this is where the pneumatic variable down force systems really shine.  The planting depth will be more uniform across soil type differences which leads to more uniform emergence.

On a final note fellow Pioneer sales rep Richard Cressman is holding a farm inter-generational/succession planning seminar this Thursday at the Wilmot Recreation Centre in New Hamburg.

It looks to be an informative session including a farmer panel and other experts.  To register you can call Richard at 519-588-2731 or e-mail to

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