Exactly one year ago, as I was writing my column, Canadian wildfires were building up a full head of steam (or more accurately, smoke). The maximum impact would be felt in the northern tier of the U.S. during the second week of June 2023. During that period, Canadian firefighters scrambled to put out the blazes in Quebec, where more than 160 forest fires were alive and well.

Crop Comments: Plant sorghum when corn seedlings have good colorThe fires were fueled by high temperatures and dry conditions. At that time, medical experts said that not only should we expect more record-setting wildfires because of climate change but more people placed in harm’s way from inhaling toxic smoke as well. Failing to keep carbon in our soils has helped accelerate climate change.

All three branches of the Mississippi Basin – the Mississippi River, the Ohio River and the Missouri River – experienced widespread shortage of precipitation in 2022. This watershed drains 41% of the continental U.S. For all three sub-basins in this region to be so short of water simultaneously was statistically unlikely. But it happened.

For sure, the super-prevalent corn/soy “non-rotation” liberates carbon from soil into the air as well as shunting lost soil and nutrients toward the Gulf of Mexico. Fortunately, more and more farmers are embracing sorghum, sudangrass, their hybrids and millets as forage sources for livestock. Cheaper to grow than corn (on a per-pound of digestible dry matter basis), these hot climate summer annuals (HCSAs), with fibrous root systems, also arrest soil degradation. Ongoing field research provides increasing proof that brown mid-rib (BMR) male sterile forage sorghum can successfully replace corn silage.

Prior to making this introduction, I picked the brain of Certified Crop Advisor Tom Kilcer. His first year as Agronomy Cooperative Extension agent in Columbia County, NY, overlapped with my last year in that profession in Otsego County. Many of the following thoughts have been excerpted from Kilcer’s current newsletter at advancedagsys.com/may-2024.

Multiple replicated male sterile sorghum trials, with proper nutrient-enhancing and delayed harvest, were conducted in several states. Workers found this crop has the ability to produce, at less cost, nearly the same milk as corn silage, with better components.

Conventional (non-organic) dairy farms found that it is 90% cheaper seed cost-wise to grow sorghum than corn silage; that’s before factoring in all the fungicide sprays needed for corn but not sorghum. Corn stops growing at 85º while sorghum grows up to 105º, providing more growth out of the season. Deer will hide in sorghum, coming out to eat nearby corn. Its natural prussic acid (hydrogen cyanide) kills corn rootworms, so corn can safely be planted the year following sorghum. It is direct-harvested with one cut, and with no grain you don’t have the extra cost of fuel for kernel processing.

The heads of grain sorghum plants growing on a field at Rocky Ford in Colorado. Photo courtesy of Howard F. Schwartz, Colorado State, Bugwood.org

Kilcer wrote that the first key to growing BMR male sterile forage sorghum is getting the right length of season for your location. To maximize the digestible nutrients to be comparable to corn silage, it’s critical to have eight weeks of growth after head emergence before harvesting. This is the same as normally chopping corn silage eight weeks after tasseling. We’re talking eight growable weeks.

The crop does well with immediately incorporated manure with high organic matter. The organic matter will supply nitrogen late into the season, supporting high crude protein (11% – 12% CP). For perspective, a 25-ton silage crop at 35% DM will remove 336 lbs. of nitrogen (plus critical 40 lbs. of sulfur) to support a 12% crude protein level. Shorting it drops the protein. The flip side is that you can correct lower protein by adding feed grade urea in the total mixed ration.

Kilcer stressed that the front end of the season is critical for successful stand establishment. Soil temperature must be at least 60º, approaching 65º, with warmer weather forecast for the next two weeks. If you question this temperature mandate, recall that sorghums and sudangrasses originated in sub-Saharan Africa. Some farms tried to push it in cooler weather last spring, regretting the results, especially organic farms, where weeds out competed the crop.

The advantage is that the warm weather comes after the first cutting haylage is harvested. If you push the season, it is critical not to use organic practices and to also use treated seed allowing herbicide application. Sorghum needs warm soils.

Corn demands a minimum of 50º for three to four days – none of this 45º at night business. If corn doesn’t receive that necessary soil warmth, its color will be yellower than green. Most assuredly, soil temperatures will not have reached the 65º demanded by those HCSAs.

Taking that color target one step further, when corn seedling pigment mimics the color of the most common green tractors on the planet, soil temperature can be presumed warm enough for HCSAs to enjoy a start rapid enough to dodge most weed pressure.

An absolutely essential step, based on replicated research performed in multiple states, is the population planted and row width used. The old farmer’s tale is to plant it at 15 – 20 lbs. of seed/acre which at the average pounds of seed/lb. results in 225,000 seeds/acre, or less than one inch between plants on a 30-inch row. This practice, according to Kilcer, is bad science.

About 40 years ago, there was extensive replicated research on high-population corn planting – 40,000 to 50,000 per acre. As a result, the crop fell over before harvest, like over-planted sorghum does. The smaller stems had a huge increase in percent rind (outside rim of the stem with high lignin), which greatly decreased forage digestibility. The same is true with sorghum.

Closing with a quote from Kilcer: “What we have found is that as we increased the spacing in the row, the sorghum stalks got as big as corn stalks at the same population, and the lodging issues decreased or disappeared. Yield and digestible fiber were still maintained.”