Hot Climate Summer Annuals Already?
The first questions directed to me generated by the anticipated 2023 growing season came 11 days after Punxsutawney Phil made his involuntary greeting to humanity. The question came from Ken, a grass-fed organic dairy farmer in Chenango County. He asked, “I’m considering no-till seeding Japanese millet into the land which we planted rye cover crop on the last two falls. Can you tell me how the millet compares with the sorghum in terms of dairy cow feed value?”
I told him that to the best of my knowledge Japanese millet was not available in a brown mid-rib (BMR) version. Varieties with the BMR trait have been bred (through natural, non-genetically engineered selection) to yield increased fiber digestibility. Pearl millet does have a BMR version, but the seed generally costs at least twice as much as Japanese millet seed. I told him that BMR versions of a given forage variety typically support milk production better than non-BMR versions. Since sorghum, sudangrass and their hybrids do have BMR variety options, they would support milk production better than Japanese millet. The millet works better for dry cows and heifers than the “higher octane” BMR varieties.
In favor of the millet is the fact that it is more forgiving of less-than-ideal soil fertility. A field that tests with a pH of 5.7, low phosphorus and is marginally drained will support millet much better than it will sorghum, sudangrass and their hybrids. Some agronomists refer to all four of these crop classes as hot climate summer annuals (HCSAs). This makes sense, because millets originally developed in the warmer, drier regions of China and India, and the other three annuals had their origin in sub-Saharan Africa.
Regarding no-till seeding millet into rye stubble – after first cutting baleage is harvested, I cautioned that HCSAs demand a soil temperature of 65º F. (Corn accepts, or at least tolerates, 50º.) That being the case, it may be advisable to give the attempting rye regrowth a light disking to stall out any threat of allelopathy – natural weed-killer traits. It’d be good to get a soil thermometer if you don’t already have one.
Ken’s second question read: “What seed rate do you recommend for the millet? I believe the recommended sorghum seed rate is 40 lb./acre, but we usually have much better success at ~75 lbs./acre. Should we double the millet seed rate too?”
Answer: A seeding rate of 40 lbs./acre for sorghum should be adequate if fertility is on target and the seed is drilled. When broadcasting the HCSA seeds, increase the seeding rate by 15% – 20%, then harrow it in lightly, in order to lessen the degree to which birds say thank you.
Japanese millet is a much smaller seed than the other HCSAs. Most folks get a good stand, covering four acres with three 50 lbs. bags of seed. If broadcasting the seed, increase the seeding rate by 15% – 20% and harrow it in lightly.
Here are some more management pointers for HCSAs. Research conducted Dr. Larry Chase, professor emeritus, Dairy Nutrition, Cornell, found that with proper balancing, BMR sorghum species can produce the same milk as corn silage. Work at the Miner Institute on BMR sorghum-sudan hybrids also documented the same milk production as corn silage but with higher components and greater feed conversion efficiency.
BMR sorghum species (and BMR sorghum-sudan hybrids) have numerous benefits compared to corn. Corn seed is increasingly expensive to grow. Sorghum is $100/acre cheaper to grow for just seed cost. Genetic rootworm resistance in corn is failing and disease controls require expensive fungicides. Sorghum species eliminate corn rootworm for following corn crops, are not susceptible to corn disease and are deer-proof. Sorghum kills rootworms through its secretion of prussic acid (hydrogen cyanide or HCN); HCN is bad for cows but proves fatal for rootworms. As sorghum plants mature, the above-ground portion becomes prussic-acid-free – that cannot be said of the roots.
For organic farmers, corn silage requires multiple cultivations which leave the soil vulnerable to erosion. Cultivation, critical for the crop success, is at the same time that organic haylage needs to be made. Thus, the haylage is often late, severely limiting the profit potential of the organic farm. Optimum sorghum planting is in drilled narrow rows (seven to 14 inches). Replicated research found an 18% higher yield compared to 30-inch rows. Narrow rows quickly canopy to prevent erosion, shade out weeds and maximize sunlight interception in short seasons.
Based on work done at the Miner Institute, sorghum-sudan’s rapid emergence and dense stands utilizing a stale seedbed is replacing corn silage on organic farms, without cultivation, to control weeds. Thus, more organic farms are switching to BMR sorghum-sudan as their energy forage. More and more conventional (non-organic) farmers are moving toward HCSAs – and away from corn – for the reasons just stated.
Research supported by the NY Farm Viability Institute examined various harvest stages of BMR sorghum. Results were analyzed by Professor Chase using the Cornell Net Carbohydrate and Protein Systems model. They observed that for seeded-type sorghum the potential milk increased from the boot stage as the fertilized seed heads began filling. The milk potential decreased as they compared parts of the seed head, as they went 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 for the whole plant, where a lot of energy is stored. This, in turn, is compounded by the loss of energy in hard, indigestible seeds. Thus, Chase stressed, waiting for mature grain can decrease milk production.
Looking back, we see that 2022 was a particularly good year for growing HCSAs, because there were so many days in our region with temperatures peaking in the 90s. Corn does not benefit from temperatures exceeding 85º. Sorghum is known to keep performing when heat pushes 105º!
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