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Growing sorghum this year? 5 tips for successful harvest

Don’t let your crop reach full maturity and try using directionless corn heads.

August 6, 2019

5 Min Read
A chopper harvests sorghum Sudan, short BMR pearl millet and brachytic dwarf BMR sorghum
CLOSE TO THE GROUND: This chopper is harvesting sorghum sudan on the right, short BMR pearl millet in the center and brachytic dwarf BMR sorghum on the left. Watch your speed and keep the head close to the ground if you plan on harvesting these crops for silage this season. Photo courtesy of Tom Kilcer

By Tom Kilcer

For many farmers, this year’s harvest will look a lot different from years past.

Many farms are growing sorghum or sorghum species for the first time. Its harvest timing is very different than corn silage if you want to get it right. In addition, there was a lot of silage planted in June and July. This corn could be very immature when it is harvested.

Compounding the problem are multiple weather reports that are saying cold temperatures will return with a vengeance this year and that the possibility of an early frost or freeze is above average.

Immature corn silage is a lot like sorghum or sorghum sudan. It will be a wet, higher-sugar, low-starch forage. Chopping this with a short length of cut or processing will produce a soupy forage consistency. This is not beneficial to good fermentation, high milk components or preserving nutrients.

The good news is that there are steps you can take to minimize these potential problems.

Harvest before full maturity

Research that I’ve done in conjunction with Cornell University has found that there is no advantage to waiting for grain maturity. In fact, there are many disadvantages.

The first is lodging, which increases dramatically as the seed head matures. In our research we found that even the lodging-resistant brachytic dwarf BMR sorghum fell down soon after the tip of the seed head moved to soft dough stage.

Second, if the seeds move to harder dough stage they become too small for the cow to process. Compounding this issue is a significant decrease in fiber digestibility as we move into September. Thus, waiting for matured grain can decrease milk production.

Sorghum species should be ready for harvest before they reach 35% dry matter. Many times, when the tip seeds reach soft dough they will just be reaching 30% dry matter. Our research has found that, with the proper steps, we can make perfect sorghum silage as low as 25% with no butyric acid.

Use directionless corn heads

Directionless corn heads will chop sorghum very effectively, especially if the plant is more than 4 feet tall.

We have direct-chopped sorghum, sorghum sudan, sudangrass and pearl millet. The harvest head needs to be down on the ground to get as much of the crop as possible, as it is all highly digestible forage.

Watch your forward speed. You will quickly pass the cutting speed of the head, which will leave longer stubble in the field and a potential yield loss. Longer stubble is an immediate 10% to 15% yield loss of highly digestible forage from driving too fast.

Plants that do not have a stem, are head emerged and are shorter than 5 feet tall will be all leaf and will not feed very well. These fields may need to be mowed to a windrow and chopped with a haylage head.

We don’t suggest drying it wide swath as it is too thick and difficult for tedding. The wide swath will also mix more dirt and contaminates when you try to rake or merge to a windrow.

Watch your cut

Rick Grant, Miner Institute, has found that as forage quality decreases, the shorter the length of cut will lead to greater milk production from poorer forages. The reverse is true for highly digestible forages, such as BMR sorghum species and immature corn.

The smaller they are chopped, the faster they are flushed out of the rumen before the cow gets the full extent of digestion. Larger particles will stay in the rumen mat until the bacteria can extract most nutrient components.

The other problem with chopping these silages too fine and processing them is that the higher plant moisture will turn them into the consistency of applesauce and produce hundreds of gallons of leachate, which removes the most digestible part of the plant.

Chopper setup is critical. We harvested at half, three-quarters and 1.14-inch cut length with 3-millimeter processing. We had excessive leachate from the smaller cuts but not the 1.14-inch length. Opening the processor to 6 millimeters (I actually suggest going wider) stopped the leachate from the three-quarters and 1.14-inch length.

Don’t process it

First, it is unnecessary as there are no hard kernels to break.

There is no increase in starch digestibility from processing the immature or nonexistent kernels; thus, it is a waste of fuel and time.

Second, mashing and tearing increases the volume of leachate and its lost nutrients.

In research supported by the New York Farm Viability Institute and with help from Dutch Hollow Farm and Wil-Roc Farm, we tried multiple cutting lengths and processing gaps to figure out what worked best for sorghum.

We chopped at 1.14 inches and took replicated samples processed at 3 millimeters (corn silage setting) and at 7 millimeters. We achieved a relatively uniform 10 to 11 pounds of dry matter per cubic foot from silage that was 21% dry matter and nearly identical particle size.

But processing had a huge effect on increasing leachate coming out of our silos: it increased more than five-fold.

An analysis of the silos found that there was a significant amount of sugar preserved at 7 millimeters over 3 millimeters.  

Inoculation is key this year

Sorghum species are a wet, high-sugar forage. Immature corn is similar.

The use of a high-quality homolactic bacteria is critical this year. Having the right bacteria ferment your forage is crucial to maximizing preservation of nutrients for the cow.

In a replicated, randomized test I ran on BMR sorghum, conducted with American Farm Products, the inoculated sorghum averaged 2.3 pounds more milk per cow per day in preserved neutral detergent fiber digestibility in comparison to the control.

Another replicated study we did using a Chr. Hansen inoculant designed for wet, high-sugar forage, and harvested at multiple replicated points, from 17% to 30% dry matter, showed no butyric acid over threshold. In fact, there was little to no butyric acid detected when the forage was 25% dry matter or more.

If a light frost hits, don’t panic. If the leaves just above and below the ear are OK, it will continue to mature.

Allowing it to continue to mature brings the nutrient status closer to normal corn silage. The downside is that with considerable frosting, the ruptured cells will leak their contents onto the leaf and attract all types of bacteria, fungi and yeast that can produce mycotoxins.

The longer you delay harvest for dry-down, the more of these organisms will grow. It is very much a judgement call, but early harvest may be better than mold.

Kilcer is a certified crop adviser in Kinderhook, N.Y.

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