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4 tips for forage sorghum success

If you haven’t planted corn silage yet, BMR male sterile forage sorghum could be a good alternative.

Tom Kilcer

May 22, 2024

6 Min Read
A field of BMR male sterile forage sorghum
GO NARROW: Drilled narrow rows of BMR male sterile forage sorghum yield 18% higher than 30-inch rows. Population and acre spacing in the row is critical to get large stalks that stand well, have high nutrition relative to the lignin-filled rind and will yield. Photos by Tom Kilcer

Have you tried brown midrib male sterile forage sorghum as a replacement for corn silage? Data have found it to be cheaper, and it can produce nearly the same amount of milk but with even better components.

Dairy farms are finding that BMR male sterile forage sorghum is 90% cheaper to grow, and that’s before we factor in all the fungicide sprays we have to put on corn.

While corn stops growing at 85 degrees F, sorghum keeps growing up to 105 degrees, so you get more growth out of the season. Its natural prussic acid wipes out corn rootworms, so corn can be planted the next year without damage.

Sorghum is direct-harvested with one cut; no need to spend money and fuel on processing.

A close up of a BMR male sterile sorghum seed head

It can be especially useful on organic dairies. Why? Organic corn needs to be cultivated to control weeds, especially when smaller. This comes at the same time haylage needs harvested to support a profitable high-forage diet. Thus, the corn is cultivated, the haylage is late, and that leads to higher costs of production.

Properly planted BMR male sterile sorghum can outgrow the weeds and does not need to be cultivated. It can support the same milk production and is planted right after haylage.

As with any crop, there are several steps to ensure success. Here are four of them:

1. Grow the right stuff. The first is to get the right length of season for your location.

We have found that to maximize digestible nutrients to corn silage levels, it is critical to have eight weeks of growth after head emergence before you harvest. This is the same as normally chopping corn silage eight weeks after tasseling.

One farm I know planted late and got the eight weeks after heading. But the last two weeks were too cold for sorghum to grow. Thus, variety selection is critical. There are limited varieties available right now.

Sorghum breeders are rapidly developing varieties for a wider range of climate zones. North of the Mason-Dixon line, there is only one variety that I know of that is less than 55 days to heading and fits that climate zone. South of the Mason-Dixon line, several companies have varieties that fit.

Unfortunately, one variety that had good genetics had quality-control issues and had seed set, ruining its digestibility. Another variety was a good male sterile variety, but its parent genetics caused it to send out heads from each of the leaf axils, which converted the highly digestible nutrients into lateral shoots with a lot of lignin and very low digestibility.

There are good, longer-season male sterile varieties out there, but you must look and ask questions.

2. Incorporate manure. The crop does well if you immediately incorporate manure with high organic matter.

The organic matter will supply nitrogen late in the season to maintain high crude protein levels of 11% to 12%. For some perspective, a 25-ton corn silage crop at 35% dry matter will remove 336 pounds of nitrogen, plus 40 pounds of sulfur to support a 12% crude protein level. If you short it, the protein drops. The flip side is that you can correct lower protein by adding urea in the total mixed ration.

3. Plant in warm soils. The beginning of the season is critical for successful stand establishment. The soil temperature needs to be above 60 degrees, approaching 65 degrees, with warmer weather forecasted for two weeks.

Some farmers tried pushing it in cooler weather last spring and regretted the results, especially organic farms where weeds out-competed the crop. The advantage is that warmer weather usually comes after first-cut haylage has been put in storage.

If you push your planting date, then it is critical to use treated seed that allows herbicide application.

4. Go narrow. An essential step we are conducting replicated research on is population at planting and recommended row width.

There are bad recommendations out there. An old farmer’s tale states that you should plant at 15-20 pounds an acre, which results in about 225,000 seeds an acre, or less than 1 inch between plants on a 30-inch row. The theory was that this increases yield and that the smaller stems are more digestible. Not true!

In the early 1980s, there was considerable research on high-population corn plantings at 40,000 to 50,000 an acre. The result was a crop that fell over before harvest. The smaller stems had a huge increase in percent rind (outside rim of the stem with high lignin). This significantly decreased the digestibility of the forage, and the same will happen with sorghum.

What we have found is that as we increase row spacing, the sorghum stalks got as big as corn at the same population, and the lodging issues decreased or disappeared. Yield and digestible fiber were still maintained.

Our hypothesis is that 7.5-inch row spacing, 120,000 seeds per acre is the maximum you should go with. This results in plants that are 7 inches apart in a row that is 7.5 inches wide. This is nearly equidistant spacing to maximize yield, quality and standability while shading the ground to prevent weed growth.

If you use 15-inch spacing with sorghum plates, you still need that minimum 7 inches in the row to prevent thin lodging stalks. That is achieved at 60,000 seeds an acre. With GPS technology, you can plant a 15-inch row and double back to split the rows to get accurately planted 7.5-inch rows.

We do not suggest you plant sorghum in 30-inch rows. In my replicated trials, it yielded 18% less than narrow 7.5-inch drilled rows. If you insist on 30-inch spacing, we suggest the same 30,000 to 34,000 seeds as corn to keep the crop standing and to have stalks that maximize digestible content.

A woman stands in front of a tall field of BMR male sterile sorghum

In my research, I have seen a hurricane hit after the plants headed out. Because it was planted at the correct population, in two weeks it was three-quarters back to standing upright. At harvest, it was nearly all upright. This will not happen if you plant too high a population. It will go down and stay down.

We suggest planting depth be set at 1–1.25 inches in warm soil. Once emerged, it can grow at a tremendous pace. Mine doubled in height each week. When it was 14 inches tall, I measured it and calculated that it had grown 3 inches a day over a week.

BMR male sterile forage sorghum is not a magic crop, but it has huge potential to make dairy rations more profitable. As with any crop, key management principles need to be followed.

Kilcer is a certified crop adviser in Rutledge, Tenn., formerly of Kinderhook, N.Y.

About the Author(s)

Tom Kilcer

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

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