A Tale of Two Crops

While the title is a not-so-subtle reference to Charles Dicken's novel, there is a lot less intrigue in this case.  The results of the very dry seedbed combined with a lack of meaningful precipitation in the week or weeks following seeding have become very visible in wheat, barley, and oat fields in the last week or so (Photo 1). At first glance, this may look like a mix of two different varieties of wheat. A closer inspection makes you realize that this is the same variety at completely different growth stages rather than two different varieties.  

Photo 1 - A field of spring wheat near Crookston with two crops that are more than a week apart in their growth and development

The challenge ahead is how to harvest these two crops without either an increase in dockage, a loss of quality, or both. The published data on the effect of swathing grain prior to physiological maturity (the point in the development of the crop where the maximum dry weight has been accumulated in the kernel and the only thing left for the crop to do is to dry down enough to allow for mechanized harvest) is pretty straightforward - the earlier you swath during the grainfill the greater the yield loss and loss in test weight will be; not until kernel moisture is below 40% can you expect to not loose grain yield or test weight. That moisture content is not reached until well into the soft dough stage. Swathing the grain in the watery rip or milk stage resulted in kernels that were shriveled and retained a green color.  

Leaving grain standing past the harvest ripe stage increases the risk of eventually having the crop getting rained on (if we can only be that lucky in the case of the row crops).  This will initially only result in a loss of test weight. Repeated wetting and trying, however, may lead to loss of post-harvest dormancy and increases the risk of sprouting.  That in turn, results in low Hagberg Falling numbers.  Eventually, the straw will be overripe and collapse, impeding harvestability even further.

What's one to do?  The decision will largely depend on the developmental gap between the two crops, the preharvest sprouting tolerance of the variety, and the intermediate weather forecast.  The larger the gap between the two crops and the greater the risk for preharvest sprouting (either because the variety has a poor rating and/or because frequent rains are forecasted) will force your hand to focus on the first crop. 

If you choose to swath the crop there is a good chance the unripe kernels will dry down in the swath and the shriveled kernels will be blown out the back of the combine.  Application of preharvest glyphosate in wheat in this case would be considered an off-label application as not all of the wheat plants will have reached physiological maturity.  Straight cutting will result in a mix of dry and very wet grain in the tank and ultimately in the bin. This will require immediate drying of the grain to avoid spoilage.  The closer the individual kernels are to physiological maturity to more likely it is that those kernels will cure out normally and not retain a green color. Check here for all the in and outs of drying wheat and barley.