Crop Comments: Sorghum, sudangrasses, their hybrids & millets, in the final stretch

In horse racing, the final stretch is the last straightaway of the track leading to the finish line. I like to compare growing seasons to horse races.

Much of the corn in the Northeast has been affected by drought, suffering lower starch build-up levels due to less water during July. But, of late, most areas have received (and are still receiving) enough rainfall. In the latter areas, growers are seeing corn’s whole plant dry matter continuing to increase. In moisture-deficient areas, cobs won’t have much more space to fill out. That scenario spawns lower yields, lower starch/energy values and lower bushel weights.

Corn is a lot more sensitive to very limited moisture levels than hot climate summer annuals (HCSAs).

As you read this, all but the longest season corn varieties (and/or really late-planted stands) are quite well dented and would fare quite well should an early frost hit. Corn is a member of a grouping of plants called C-4s. But let’s target our discussion on other members of this HCSA “club.”

Sorghum fits in this category, along with sudangrass, sorghum/sudangrass hybrids and millets. They are all C-4s (along with corn and sugarcane). C-4 means that their “body” tissues consist of four-carbon modules. C-4 species are much more efficient at conserving moisture than is the case with non-C-4 species. (Of this grouping, millets (particularly Japanese) appear to thrive better than these other C-4s with less than optimal soil fertility.)

Not surprisingly, more farms are now growing sorghum or sorghum relatives and millets. Their proper harvest timing differs from that of corn silage. Sorghums can be wetter, high-sugar, low-starch forage. In a properly balanced ration, sorghum can support the same milk, at potentially less cost, than corn. Chopping sorghum with a short length of cut, and worse, processing, will produce forage the consistency of cooked oatmeal – not beneficial to good fermentation, high milk components or preserving nutrients (lost leachate is 100% digestible). The good news is there are steps to take to maximize results and minimize potential problems.

Replicated research supported by the New York Farm Viability Institute examined various harvest stages of brown mid-rib (BMR) sorghum. The results were analyzed by Professor Larry Chase using the Cornell Net Carbohydrate & Protein Systems model. Chase and his team discovered that for seeded-type sorghum, milk potential increased from the boot stage, as the fertilized seed heads started filling. The milk potential decreased as they compared parts of the seed head, going from the tip of the seed head, just starting soft dough to soft dough halfway down the head. This is because at the soft dough stage there are significant decreases in fiber digestibility of the whole plant, where most energy is stored.

This, according to Chase, is compounded by loss of energy in hard, indigestible seeds. Thus, waiting for matured grain can decrease milk production. For sorghum species, the chopper cut length setting is critical. At Chazy, NY’s Miner Institute, research on effective fiber and feed quality found that as forage quality decreases, shorter length of cut is associated with greater milk production from poorer forages. They found that the reverse is true for highly digestible forages such as flag leaf triticale and BMR sorghum species. The smaller they’re chopped, the faster they’re flushed out of the rumen before the cow “enjoys” the full extent of digestion. Larger particles stay confined in the rumen mat until rumen bacteria extract the majority of nutrients.

The other problem with chopping these silages fine is it increases the number of plant cells cut open and, especially if processed, releasing hundreds of gallons of leachate from storage. This liquid (besides making a smelly mess) removes the most digestible part of the plant. (As stated earlier, it’s 100% digestible.) Additional cuts, with shorter chop length, open more plant cells for the liquid to run out. Chase’s team harvested sorghum species at 0.5-, 0.75- and 1.14-inch length of cut, with no processing. As long as they did not process, they observed excessive leachate from the half-inch cut, but not from the other two cut settings.

I believe that 2026 has been a good year for growing sorghum, sudangrasses and their hybrids, because there were so many days in our region with temperatures in the 90s; corn does not benefit from temperatures over 85º. Sorghum is shown to keep performing with heat pushing 105º – not surprising, since the crop originated in sub-Saharan Africa.

Additionally, in terms of soil structure health, HCSAs outperform corn because of their fibrous root systems, which corn lacks. (Fibrous root systems are instrumental in building up soil organic matter.) Another plus for sorghum species is that their root systems secrete prussic acid (hydrogen cyanide or HCN), which carries over into the next year in the rotation. That’s a good time to plant corn, because HCN kills corn rootworm.

The C-4 trait is not always beneficial to crop people. For example, at least two weeds enjoy that trait. The most well-known one presently is Palmer’s amaranth (Amaranthus palmerii), which can tolerate heat extremes. Sadly, A. palmerii, a broadleaf, has also become resistant to almost every herbicide in modern chemical arsenals. Fortunately for us, to date, A. palmerii hasn’t been able to colonize much Northeast farmland.

Another annoying weed, this one in the grass category, has the scientific name Sorghum halepense (a cousin to all the other sorghum species). According to Charles Walters in “Weeds: Control Without Poisons,” S. halepense “is an annual or perennial with both seed and rhizome reproduction. Its fibrous root system allows it to exercise a vicious reproduction cycle, with few if any geographical limitations.” S. halepense (aka johnsongrass) is a C-4 plant, but, as an invasive perennial weed, it is not cultivated as a crop.

According to the Herbicide Resistance Action Committee Global weed fact sheet, S. halepense is “a C-4 species well adapted to hot, dry environments.” This means it uses the C-4 photosynthetic pathway, common in many warm‑season grasses, and allows efficient photosynthesis under high temperature and light conditions.

I first encountered johnsongrass in 1976, when, as a New York county agent, I was hosting a busload of Otsego County farmers studying southern Pennsylvania dairying. My Extension counterpart showed us a stand of johnsongrass which had developed resistance to triazine herbicides – my introduction to a nascent nightmare.

by Paris Reidhead