Tuesday, March 1, 2011

What About Soybeans?

The chart above shows average corn and soybean yields from the US over a 25 year period from 1984 to 2009.  Corn yields increased an average of 1.6% over this period, while soybeans increased 1.27% over the same time.  The slower incremental gain in soybeans has frustrated breeders and agronomists alike.  Some have suggested that soybean yields have suffered because it has been assumed for too long that soybeans are easy to manage.  This hits close to home because I have been known to tell new soybean growers to put the seed in the ground, control the weeds and send in the combine.  Piece of cake, no fuss, no mess.

The past few years we have started looking at soybeans with a more critical eye because corn is putting more money in our pocket.

What factors should we consider to boost soybean yields?

Planting Date

Corn growers have not been afraid to push planting dates earlier, but there has been general reluctance to do the same with soybeans.  This chart is a summary of 23 site years of data showing the yield advantage to earlier planting dates.  Here in Ontario, April 15 is probably too early, but May 1 is not.  Ealier planting dates work with because the plant will be physically bigger at the end of June when flowering begins.  A bigger plant supports more flower retention and less pod abortion.

Variety Selection and Planting Practices
Variety selection is crtical and must be matched to disease tolerance needs like white mold and phytopthera.  I believe soybean breeders will eventually break through and start delivering greater yield gains with newer genetics.
A common question from clients relates to row width response between varieties.  There is a feeling that shorter varieties belong in narrow rows and tall, bushy varieties are better in wide rows.  Personally, I don't like big tall varieties and I don't like short varieties.  Neither type tends to be very consistent.  A good variety is a good variety, I don't care what row width you use. 
A bigger factor influencing soybean yield response in my opinion, is uniform emergence.  We do in this with corn and we should do the same with soybeans.  Emergence is influenced by seed bed conditions, uniform seeding depth and trash cover. 

Soybeans consume a lot of fertility.  A 50 bus soybean crop consumes 45 lbs phosphorous and 65 lbs potash.  A 150 bu corn crop consumes 57 lbs phosphorous and 40 lbs potash.  The problem is soybeans do not respond to starter fertilizer as well as corn does and we tend to neglect fertilizer applications to soybeans, especially on rented crop land.  If your soil test levels are high for both P and K, this neglect will not hurt you.  But, most of us do not have high P and K, so we need to pay closer attention to fertilizer applications for soybeans.

Weed Control
I am appalled when I see growers no-tilling soybeans without early weed control.  This drives me nuts.  KILL THE WEEDS, KILL THEM EARLY.

There are new inoculant products on the market which are worth the money.  We will be using Optimize this spring which we believe will deliver 1-2 bus more than traditional inoculant.   More on this later.


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