By Dr. Jason Kelley, Wheat and Feed Grains Agronomist
As many of you are becoming aware, the rain event last week has caused much of our grain sorghum to sprout in the head. The extent of damage is still to be seen, but based on the limited acres that were planted this year (40,000) and the number of calls; it appears a majority of the acres are impacted from most areas of the state. Early planted fields, April through mid-May are most impacted by the rains and approximately 80% of our grain sorghum was planted during this time period.
Once grain sorghum is mature, extended periods of rainfall with warm temperatures can cause sprouting of the grain in the head. Some areas of the state had 8 consecutive days of rain last week with no drying weather. The closer the grain was to harvest, the more likely it sprouted. Later planted fields or areas of fields that maturity was delayed may show very little sprouting compared to grain that was more mature. Even on individual heads I have seen grain in the top of the head sprout and the grain at the bottom not, showing how relatively small differences in grain maturity can affect sprouting. There may be hybrid differences in sprouting, but maturity differences are likely the largest factor in sprouting. Sprouted grain is more prone to shattering, and you will likely see a considerable amount of grain on the ground. Many of our grain sorghum growers would have started harvest last week on early planted acres, so the timing of this rain is very unfortunate. The Arkansas Agriculture Statistics Service in the August 15th report estimated that only 1% of the grain sorghum crop had been harvested.
Will my grain be marketable? This is the biggest question and unknown at this point as harvested samples have not been evaluated yet. A majority of the grain sorghum grown in Arkansas is exported, especially the areas closest to the Memphis and Helena markets. Grain sorghum that is exported will follow current grain grading guidelines. If damaged kernels (including sprout damage) are greater than 15% of the grain, the sample would be classified as sample grade (poor quality) and the grain price would be heavily discounted or the grain would be rejected. Unfortunately, many fields that I have seen and pictures that I have been sent are showing more than 15% sprout damage.
Grain that is being utilized in the livestock/poultry markets will still have feed value, even though it is sprouted. In poultry and livestock feeding trials conducted by other universities, animal performance was not noticeably affected by sprouted grain compared to high quality grain. The following link provides an in-depth discussion and results of a Texas poultry feeding trial utilizing sprouted grain sorghum. http://amarillo.tamu.edu/files/2010/11/SproutedsorghumChickenFeed.pdf
In these feeding trials mycotoxins were NOT detected in the sprouted grain. However, in our environment, mycotoxin development such as aflatoxin or vomitoxin has the potential to be an issue. A mycotoxin test should be performed prior to feeding sprouted grain to livestock or poultry.
Should harvest aids be used? Once grain moisture drops to a harvestable level, grain sorghum should be harvested as soon as feasible to prevent further reductions in grain quality and reduce grain loss from shattering. The use of a harvest aid to speed harvest may be warranted, especially if overall quality of the grain still appears to be acceptable. Harvest aids will stop plant growth as well as sprout growth, but the damage to the seed has already been done. With ample soil moisture and warm temperatures, secondary heads will soon be emerging (or already emerging) if harvest is delayed more than it already has been, further complicating harvest. If grain quality still appears acceptable and secondary heads are emerging, a harvest aid should be strongly considered to shutdown growth and facilitate a quicker harvest.