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Frequently Asked Questions
Concerning BMR Sorghum Sudan
Bmr stands for Brown Mid Rib. BMR sorghum sudangrass has a characteristic yellow –brown leaf mid rid, which is marker for its other genetic trait, reduced lignin content. This is a marker gene that turns the rib on the underside of corn, sorghum, and sorghum-Sudangrass brown. What is exciting is that it is also a marker for low lignin, very high digestible forage. Historically sorghum sudangrass has been grown on limited acreage as a "rescue" crop where emergency forage is needed. You have probably heard of bmr corn. It is very highly digestible, yields 20 – 25% less than normal corn, and falls flat with the least wind. The low lignin comes with the price of low standibility, especially when you put a heavy ear half way up the plant. Bmr sorghum is similar. The main difference from corn is that instead of putting the grain head halfway up the plant, it is all the way up on the top of a 7 – 9 foot tall plant. Yes, it does go down flat. Bmr sorghum-Sudangrass is harvested before it gets a head.
(This variety has been developed using conventional plant breeding methods. It is not a genetically modified organism (GMO).)
Bmr sorghum-Sudan genotypes were lower in neutral detergent fiber and acid detergent lignin concentrations than normal genotypes. There was greater 72-hour extent of NDF digestion when compared to normal. This means that in the same time frame, and the same amount of dry matter, a pound of highly digested bmr forage will give the animal more nutrition, than the same forage without the high digestibility. This allows the animals to make greater use of the same dry matter. This can be seen in Graph 1. The bmr sorghum-Sudan fertilized at 120 lbs.N/A had more total digestibility than average corn silage(CS avg), or non- bmr sorghum-Sudan(NON BMR) (and much more than poor corn silage(CS min) – no one reading this ever makes less than perfect corn silage). The total digestibility rivaled the best of the best corn silage (CS max)(which is the fall-flat bmr corn silage type).
The digestibility of corn silage NDF, is considered excellent if it is over 45% dNDF. The bmr sorghum-Sudan ran 69.6% dNDF as you can see in Graph 2. While bmr sorghum-Sudan does not have the grain, therefore has a slightly higher NDF, it makes up for that in digestibility.
As you can see in Graph 3, the in-vitro NEL of bmr sorghum-Sudan is slightly above average corn silage, but not as high as the best of best corn silage. A study in 1987 showed that a similar crop, bmr sorghum would support the same milk production as corn silage would. We found in an on farm experience in 1998, switching from corn to bmr sorghum-Sudan, milk production was maintained without change. Work by Steve Hadcock, dairy Extension agent in Columbia county and confirmed by Dr. Larry Chase of Cornell University Department of Animal Science, found that very high forage feeding levels (>70%) could be achieved for high producing cows, with bmr sorghum-Sudan.
graph 3
The added bonus that we found is that with proper fertilization, the crude protein is well above even the highest values found in corn silage – better than some haylage I have seen. (Graph 4) Because this protein is in a matrix of very highly digestible forage, it has the ability to produce a tremendous amount of microbial protein. This could reduce or eliminate the expensive by-pass protein additions in your concentrate.
graph 4
There are several other practical reasons for considering bmr sorghum-Sudan. One of the first is that it will produce a profitable crop where you couldn’t before. The last breakeven cost of growing corn silage that I saw a number of years ago was 13 ton/A. Costs have not gone down since then. Fields below breakeven, are like low producers in your milking string – they just cost money and take space. By switching to bmr sorghum-Sudan, these fields can contribute to supporting high milk production for increased profitability. The trade off from growing corn is that you don’t need a corn planter, a corn head, or herbicide cost. You do need to use a drill, haybine, and haylage head on your chopper to harvest two cuttings. The costs just about cancel the savings from not growing corn – until you factor in the potentially higher milk per acre.
A second reason that producing bmr will result in a profitable crop is one of theory vs. reality. Yes, you can grow corn, but can you harvest it at the peak quality every year? As a number of farms found out this year, the best corn crop becomes sawdust with grain mixed in, when weather delays harvest. The bmr sorghum-Sudan is harvested once in July and again in the fall. The July harvest puts half the crop into safe storage before the weather turns bad. The September harvest does not have to wait for a certain milk line on the grain before you harvest. Thus you harvest when you are ready instead of waiting and risking bad weather. Preliminary work indicates that the harvest window is very large as long as you don’t let it head out.
graph 5
When evaluated on a whole crop basis, a 13-ton/A bmr sorghum-Sudan crop will produce the same milk/acre as a 15-ton/acre corn silage crop. (Graph 5)
The seeding rate we used in 1999 was about 50 lbs./acre. (Graph 6) Because little research has been done on this, we will look at various seeding rates in the future. The seeding rate impact is primarily in the first cutting. In the second cutting re-growth, each plant produced from 3 to 12 tillers each and completely filled in the gaps. It is known that with sorghum, earlier planting produces more tillers, and so you don’t need as high a rate as later planting. We don’t know if this is true for bmr sorghum-Sudan.
THE KEY IS IN THE PLANTING,IT APPEARS VERY SENSITIVE TO SEED DEPTH. You want to plant it like a seeding, into a firm seedbed, drill the seed ¼ to ½ inch deep and use the same fertilizer as corn.. Going over a broadcast seeding with the roller and the teeth slightly down will bury it too deep. The best broadcast was a field that was rolled, rained on, and then seeded and rolled again. The drilled stands that were planted like legume seedings, had excellent stands.
graph 6
Plant it when you plant corn, the first half of May. It grows rapidly. In our research plots and on farm experience, we found no need to spray a herbicide for weed control. Once the stand was out of the ground, it grew rapidly.
Bmr sorghum-Sudan is based on two crops, sorghum, and Sudangrass, which were adapted to grow in very dry conditions. Our experience and yields indicated above were in the face of 1999’s drought in the North East. There was very little leaf rolling. The lack of adequate fertilization (nitrogen) was the main limiting factor.
Fertility, especially nitrogen is very critical. As we increased nitrogen rates, the digestibility and crude protein went up, and the NDF went down. Total yields increased 10% at the 120-lb.N rate, and 29% yield increase at 160-lb.N rate. At 120N the first cutting alone removed 112 lbs. of N as protein. The fields that were manured responded much better because of the slow release of N. The year 2000 research will look at a split N recommendation, with half put on at planting and half put on after the first cutting. The latter opens the window for summer manure application, especially for those with manure storage units.
The present recommendation for harvest is after it reaches 30 inches tall. We waited until just before heading. This was about July 17 for a crop planted May 17. We delayed the harvest so that we can keep the number of harvests at two. More harvests may affect quality, but also will decrease yield and increase cost. The second harvest was at the end of September. It appears that, like most crops, bmr sorghum-Sudan does not grow much during September, and the growth it does put on is very highly digestible sugars.
Harvest this crop in mid July and in September. It appears it maintains quality over a very wide harvest window as long as it doesn’t head out. Bmr sorghum-Sudan is harvested with a mower conditioner and haylage head on the chopper.. Because of the low lignin, its a breeze to harvest. Very high quality forages such as these, are fragile. The cutting length needs to be 3/4 – 1.5 inch to maintain effective fiber. You may have to open the rolls slightly to allow the large volume of material to pass through. At harvest the plant is approximately 85% moisture. The two cut system allows summer manure to supply much of the second crop N. It needs to be reduced for proper fermentation. Concern for Prussic acid is very over-hyped. As long as it is fermented (not fed fresh) there is no danger. The swathers should be set at least as wide as the pickup head on the chopper. This will speed the drying and preserve the high Nel in the plant sugars. You need to watch the cutting length because it is easy to grind it into the consistency of applesauce. By using a 3/4 – 1.5 inch cut you can maintain effective fiber in the rumen.
Storing it in an upright silo, or putting it through an auger type mixer wagon, will achieve a long cut length to maintain effective fiber length. Very high quality forages such as these are fragile, easily broken down with each handling.
Feeding is the easy part. Bmr sorghum-Sudan has very high palatability – the cows like it. Its high quality allows for very high forage feeding levels. This supports high milk production with low concentrate cost.
The seed is readily available. The original selection produced bmr sorghum-Sudan varieties with a range of digestibility. We plan on testing the available varieties in a side by side comparison to determine if they are equal in producing high quality forage.
Bmr sorghum-Sudan is an intriguing crop. It appears to have tremendous potential. Whether that potential is realized in a practical, economic system is still being determined. If you are interested in trying this crop, please give me a call. We are trying to expand our experience base over the widest range of conditions, and you can help.
Tom Kilcer, Field Crop Educator, Rensselaer County CCE, can be reached by
calling (518)272-4210 or by email at 
.
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