What Temperatures Mean to Maturity

Everyone is now starting to talk about harvest and when is it coming.  We had a late start this spring.  As the summer has progressed, it looked like the crop was coming on very well.  The cold nights in the last couple of weeks have slowed things down so all of us are looking at what our crop is going to coming into the fall.

Growing degree-day can be defined as a day on which the mean daily temperature is one degree above the minimum temperature required for the growth of a particular crop.  The base for the cereals that we grow is generally considered to be at 4 degrees Celsius.  Newer research is indicating in all cool season crops, we are seeing growth at temperatures that are below this level. If the lower temperature is used, the amount of accumulated growing degree days goes up significantly.

These calculations become important when trying to predict maturity of the crops in the fields of the area.  The first factor that must be known is when the seeding date was.  This date is critical because it is the date when the plants started to grow.  This means that if heat was present, the plants would have some growth occurring the next day if the temperature was above the base line levels required for the crop.  The accumulation of this heat would give us an idea of how close we are to maturity for a specific crop.  The average accumulation for the Meadow Lake weather data is around 1550 growing degree days using 0 degrees Celsius as the base line temperature.  For cereals, we require an accumulation of around 1500 growing degree days that do not include a killing frost.  My guess is that most of the fields that we planted by May 25 have accumulated upwards of 1,100 growing degree days this season. We still need some heat in August to get to the levels of growing degree days that we require to get our crops to maturity.

As we all know, we cannot control the weather.  I use these numbers to talk to producers about when they can expect to get things happening in their fields. These numbers give an indication as to when fields should be sprayed pre-harvest to maintain quality.  It also gives a producer an idea as to what the risk is for a specific crop will be to get it too harvest.  With what I am seeing out there this season, most of the fields will be past the risk of frost by the first of September if we use proper management practices that help speed up maturity.

As we get closer to harvest, look at the tools that are available for speeding up maturity.  Pre-harvest glyphosate is a tool that has many benefits, one of which is providing an earlier date where harvest can occur.  Look at the tools available and make the right best decision.  Quality and yield must both be considered to ensure that the most profitable bushels are harvested.


By Dave Cubbon, P Ag