By Roger Don Gribble
ENID, Okla. —
You can tell by the headline on this article that, yes, I am a kinder, more gentle Oklahoma Cooperative Extension Service area agronomist.
It wasn’t 15 years ago I would tell producers to kill their grain sorghum and harvest within seven to 10 days after killing the crop. Since we are in a more politically correct world now, we discuss with producers the art of “conditioning the crop for harvest.”
As a producer transitions from spring-planted grain sorghum into planting wheat this fall, they will want to condition grain sorghum for harvest. This is especially important with the amount of moisture received during the months of July and August. In many cases, the moisture received has initiated additional tillering of the grain sorghum plant, and at this time those additional tillers will add to grain yield if a producer is willing to wait until a frost to kill the grain sorghum plant.
Well, that is all fine and well, but if a producer is hoping to rotate to a small grain crop like wheat this fall, then those tillers are a problem and need to be dealt with. The additional tillers increase moisture in the harvested crop, and I have seen these tillers cause good grain to pass over the combine sieves and be dropped out the back of a combine. This might be good for quail and pheasants, but likely will not pay many notes at the bank.
Conditioning the grain sorghum crop for harvest is about the application of a glyphosate product to the crop. The application is made to the crop when the biggest share of what you want to harvest is at 30 percent moisture or less. Do note your glyphosate label restriction will indicate a harvest restriction of seven days.
The biggest question for producers would be to know when the crop he wants to harvest is at 30 percent moisture. The plant gives us several opportunities to know when this moisture level is obtained. The first one is the drying of the glumes that protect the seed and hold it in place. As those glumes mature they dry out and separate from the seed. That is an early indication you are at 30 percent moisture or less.
Another timing signal is when grain sorghum reaches black layer. As you remove a seed from the plant, look closely at the point of attachment on the grain. If you see a black dot at that point of attachment, you are at the black layer stage of growth. This is a point where there is no more water being moved into the seed.
At this point, the seed is simply at its dry-down stage and harvest will begin as soon as moisture levels in the grain will be accepted at your grain handling facility.
Kansas State has done the most recent research on this topic. Jennings and Roozeboom indicated this production technique did reduce harvested grain sorghum yields by roughly 2 percent compared to the non-treated check treatment. The wheat yields behind the treated grain sorghum increased by 13 percent or five to six bushels per acre compared to the non-treated grain sorghum/wheat rotation.
If a producer chooses to utilize this production technique, be prepared for harvest after that seven-day glyphosate treatment. This technique will damage the stalks of treated plants and the chance for lodging increase significantly.
Your OCES ag educator can assist you with the timing of application to determine if your grain sorghum should be conditioned for harvest.
Gribble is Oklahoma Cooperative Extension Service northwest area agronomist.