Photoperiod Sensitive (PPS) Sorghum Sudan (SxS) crosses are a useful forage for dry cows and heifers. PPS is a Non-GMO trait of the sorghum family. The trait prevents the plant from going reproductive (heading out) until the daylight gets shorter than 12 hours and 20 minutes. This occurs each year about mid-September (depending on your latitude). If we want the highest dairy-quality forage, SxS must be cut several times a summer (usually when it gets 40 inches tall), but when we are feeding heifers and dry cows, we use a single-cut system.
The advantage of this is, when we are growing feed for heifers and dry cows, there is a big yield bonus for the one-cut system is yield. When SxS is cut several times during a season, after each cutting the plant needs to regenerate before it is off and running again. This impacts total yield. The yield advantage of the one-cut system is 2 or more tons dry matter and the reason we use PPS sorghums is to prevent heading out. The single cut also lowers harvest costs over multi-cut systems. Digestibility is still good (especially for heifers and dry cows) although the uNDF240 pool is too large for high inclusion rates in high-group milk rations.
PPS BMR Sorghum Sudan is a very economical crop to grow. Even with land and harvest costs, many farms are able to grow it for less then 5 cents per pound of DM. This combined with the rotational benefits of Sorghum Sudan has driven the growth of PPS Sorghum Sudan acres on progressive dairies over much of the country. The Johnson’s are one of those dairies.
So, What’s Happening on the Johnson Farm?
Johnson Farms, LLC, Daggett, MI, (yes, in Upper Michigan!) is operated by Dave Johnson, his brother, Dennis and David’s’ two sons, Cubby and Christian. They farm 5000 acres and milk 2,400 ProCROSS cows with a 95 lb. Energy Corrected Milk (ECM) average on a 63% forage diet. Plus, they raise all their replacement heifers and some steers.
Well, Daggett, Michigan is not in the middle of the corn belt and not anywhere near where you would expect to find sorghum growing! Daggett is 80 miles north of Green Bay, Wisconsin and 25 miles into the Upper Peninsula of Michigan. However, for the last three years, the Johnsons have been growing a bunch of acres of BMR, PPS Sorghum Sudan! It is now a major part of
both their heifer and dry cow diets.
The SxS is no-till drilled after the winter triticale or cereal rye is harvested and usually goes in after the first week of June and as late as June 15th. Glyphosate is applied to finish off the triticale or rye, and manure is applied prior to planting. The fertilization program includes the manure and a mixture of Ammonium Sulphate (AMS) and urea. Sorghums need between 10% and 20% (including the sulfur in the manure) as much Sulfur as Nitrogen to raise crude protein (CP) levels. Omitting the Sulphur will hurt. CP levels even when extra N is present, according to Tom Kilcer, Advanced Ag Systems researcher.
The crop is harvested just before corn silage is chopped. It is first mowed by a 15-foot-wide self-propelled windrower with steel conditioning rolls. A new Kuhn merger is used to merge a single windrow into the next. Remember this forage is similar to corn silage tonnage and a big job for a merger! Harvest dry matter target is 65-75%. A homofermentative preservative is used.
SxS is planted on the poorer ground on the farm and corn is planted on the better. Also, SxS is planted where the worst deer damage has been done to corn silage in the past. The harvested feed will typically have 11 to 12% crude protein, 60-65% NDF and 60-65% NDFD30.
For the breeding age heifers and up, the diet is mostly SxS plus some peas and oats and some mineral. Younger heifers get some concentrate added.
The far-off dry cow diet uses the PPS sorghum sudan but also has some grassy hay. SxS grown on low potassium land is segregated for these cows. For the close-up diets, some corn silage is added and the diet is balanced for DCAD.
So, what about soil quality?
Warm and cool season grasses have been used on the Johnson farm for about 5 years. Soil tests are only done every three years; thus our best indication of soil quality is two things. First, the hard pans seem to have disappeared. Planting is much easier, and the soil is becoming
more mellow. It is still not corn belt soil, but we are getting there! Second, there are now abundant earthworms, something that were not prolific before the grasses. Since you don’t have to go very far in the Upper Peninsula to find a fishing hole, this has to be a good thing!
The Johnsons are doing some No-till as well as minimum tillage on their farm with a vertical tillage tool. Their move to alternative forages have helped them to reduce tillage needs on their farm.
What is next for PPS?
There are some exciting things coming down the road for BMR PPS. Forage Innovations have started testing PPS sorghums planted three weeks after “Better Than BMR” corn hybrids in the same field as a one-cut, one-crop solution for forage. It has been tried on a few farms, usually in emergency situations. The idea is to use a Roundup Ready® hybrid with great ear flex and stalk expansion, plus floury kernels.
Plant the corn so that you can expect soil temps to be right (60ºF soil temperature) in three weeks. Take care of the weeds, drill in the PPS SxS. We end up with a forage with nearly30% starch, a bunch of digestible NDF and about 9-10% crude protein. It is a much better crop than pure corn silage for a one forage situation. We will be developing our management strategies for this crop in 2023.
One other advantage which any sorghum crop has is its ability to improve on next year’s corn crop. The details are the archives of forageinnovations.guru under the title of Why Following Sorghum-Sudan with Corn is such a Good Idea.