Optimizing sorghum-sudan/forage soybean cover crop populations and screening sorghum varieties for organic cover crop performance, forage, and seed production in the Northern Great Plains region

Final Report for FNC10-828

Project Type: Farmer/Rancher
Funds awarded in 2010: $17,912.00
Projected End Date: 12/31/2012
Region: North Central
State: North Dakota
Project Coordinator:
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Project Information


[Editor's Note: Work Activities for this project are outlined in the following reports from project participants: Ray Berry, Richard Gross and David Podoll.]


We run a mixed crop and commercial cattle operation on 2400 acres of land. Half is in native grass pasture. We grow small grains and alfalfa/grass hay. We utilize rotational grazing on the home place and bring in hay from the rental property for winter forage. We use cattle to graze over crops and improve soil structure.

We rotationally grazed pastures and fields. We plant green manure crops and rotate our fields into and out of hay/grass every 5-7 years. We follow a rotational cropping system as well.

1. Optimum plant density for the sudan/soybean mix
2. Weed control or weed suppression
3. Amount of summer grazing/fall (after frost) grazing
4. Soil structure after the crop
5. Timing of planting and rate of growth

1. I laid out 4 half mile strips planting the sudan at 15lbs/acre and 20lbs/acre and the soybeans at 30lbs/acre and then 60lbs/acre. The drill has two components so we were able to vary the amounts independently.
2. We quantified the volume of material on each planting and identified the rate of weed control. The highest rate of sudan and soybean had the most volume and best weed control.
3. Year one, we grazed the vegetative stage. Year two, we windowed/baled in 3-foot bales the dried crop and recorded the available AUM (Animal Units/ Month). An AUM is worth $40.

      • 8 AUM/acre for the first year

      • 4 AUM/acre for the second year.

4. Sent samples to SDSU for testing of available nutrients and also for dangerous levels of prussic acid or high nitrates due to growth.

I had the NRCS representative, Leland Schoon, come and document the results of the trials. He noted the active dung beetles consuming the manure, while after 4 days it was not present anymore, and also the reduced number of flies.

We used NPSAS personnel to help send reports.


We prepared the ground for millet and the trial area at the same time. Then we planted the mixture of sudan and soybeans in the ratio of 15 pounds and 30 pounds, 15 pounds and 60 pounds, 20 pounds and 60 pounds, 15 pounds and 60 pounds. Because of the dry conditions this year, the soybeans didn’t sprout but the sudan did well in the good soils and nothing in the poor areas. The mixture was planted June 15-16. Because of the fear of prussic acid because of the stressed plants, I decided not to graze and windrowed it August 6 and baled it in 3-ft. bales on August 16. There were 78 bales at approximately 800 pounds. The cows and calves were turned on the millet and sudan/soybean field Sept 16. The nitrate test indicated the mixture a little high but what I observed was the cows were selective in what they ate. We only had 2 inches of moisture during the growing season yet produced 1.3 tons/acre of fodder for the cows. They consumed the bales completely leaving plenty of manure at the site of each bale. The production this year amounted to 168 AUMs of grazing, a real help in a dry year like this. The thicker stand and seeding rate is what is needed to produce the biomass for either grazing or harvesting into season small bales. This practice develops warm pasture for cows and calves when the cool season grasses go dormant; also, the weed control is excellent. Because the crop grows so fast the weeds are unable to go to seed before the cows harvest it. This is definitely a practice that is beneficial to soil and cattle making it a good follow year practice.

The results achieved were many.
1. The amount of forage for the cattle to consume was greatly increased compared to native pasture.
2. The weed control was excellent.
3. The biomass returned to the soil was a lot.
4. We had excellent gain while the cattle were grazing the forage both years.
5. We also found out that soybeans had trouble sprouting during the dry year and didn’t really contribute.

I found the mixture to be an excellent soil builder and weed control agent. It was a very good way to increase the availability of summer/fall grazing to extend the grazing season. This trial will be continued by addition of other varieties of plants. There really is no barrier, but the use of sudan-sorghum comes with a concern of prussic acid in the vegetative stage of growth. When allowed to grow to a more mature stage, that concern goes away. I would tell other farmers and ranchers that this is something to be included in your cover cropping /grazing program.

We didn’t hold a field day because of the dry conditions but gave a presentation at Northern Plains Sustainable Agriculture Society (NPSAS) Annual Conference. There was a panel discussion at NPSAS annual conference with approximately 20 people in attendance. Many questions were asked. I had good interaction with my neighbors the past two years and will continue to encourage them to try the same.


Land                $30 /acre

Seed                $48/acre

Tillage             $14/acre

Plant                $10/acre

Overhead        $20/acre

TOTAL          $122/acre

8    AUMs/acre first year

8.4 AUMs/acre second year

Soil building an undeterminded piece.

The cover crop trial used different seeding rate combinations of BMR Sorghum Sudan and Organic Viking Soybeans.

The previous year’s stubble was lightly disked in early June to knock down a few weeds that were started. The dry conditions allowed me to no-till into the remaining stubble with no further weed control needed.

The plot was planted on June 25 with a John Deere 1890 no-till seeder with a 7.5 inch row spacing. Seeding rates of Sorghum sudan at 15 pounds and 20 pounds and soybean rates at 30 pounds and 60 pounds were used in four different combinations. Each plot was one acre and was replicated totaling eight plots. The sorghum-sudan seed was in one tank and the soybeans were in another on the seeder so after each plot the seeding rate was changed until all combinations were used.

The crop emerged in about 10 days. The plot received a fast 3-inch rain in early July with little other moisture the rest of the month.

By the end of July the ground was getting very dry and the crop was about 1ft. tall with a thick stand creating a canopy to suppress most weed growth. The summer continued very dry with only a few small rains in August. The soybeans produced adequate nodules to fix nitrogen.

The trial with the higher seeding reate of sorghum-sedan (20pounds) and the higher seeding rate of soybeans (60pounds) had a thicker stand yet the soybeans still performed well with taller plants than in the other three seeding rates. With the dry year, there was not a lot of difference in performance or weed control between the different seeding rates of all the plots. The sorghum-sudan reached a height of up to 5 feet and the soybeans up to three feet tall.

The plot was grazed with 240 cow/calf pairs in mid-September along with free range to an adjoining native prairie pasture. The plot was strip-fenced with portable electric fence allowing the cattle only a few acres at a time. It was grazed for a total of 5 days and still allowed plant residue to remain in the field.

Sorghum sudan cover crop trial:

• Plot size: 40 acres
• Previous crop: triticale/hairy vetch for grain
• Green manure: volunteer triticale and hairy vetch disked April 25
• Manure: 2 tons turkey manure applied June 25
• Tillage: Six cultivations prior to manure application, timed every 7 to 10 days to prevent Canada thistle growth
• Seeding: On June 27 using an IH 100 drill, sowed a mix of Blackhawk sorghum and Piper sudan grass at a 2:1 ratio at 32 lbs./acre.
• Incorporation: Double disk August 21 and 22 at a height of 7 to 9 feet

Weather: No significant rain fell from the last week of May throughout the growing season. Total rainfall for the 2012 growing season was 8 inches, 9.95 inches since the previous September. Daytime temperatures were about average. Nighttime temperatures were considerably above average. This was our driest year since 1988.

The main purposes on our farm for this trial was to grow maximum biomass after a manure application and to use the competitive nature of the sudangrass to control perennial weeds, specifically Canada thistle.

In 2011, we ascertained that the recommended seeding rate for the sorghum sudan hybrid alone was insufficient to get a fast enough canopy to prevent some annual weeds from seeding before incorporation. This year we planted a mix of sorghum sudan hybrid and plain sudangrass at a higher seeding rate. The result was a much faster canopy closure with virtually no annual weeds surviving the competition of the sudan.

In spite of the lack of significant rain during the growing season, sufficient subsoil moisture remained for a fast, substantive, and very competitive growth. In less than 2 months the sudan was in the boot and clearly using any remaining soil moisture. Thistle growth under the canopy was weak and spindly. Thistle roots were quite thin. No further tillage was done after incorporation on August 22. It was over 3 weeks after disking that the first thistle plants appeared above ground. Very little growth was made during the remainder of the fall.

On the field where the 2011 trial took place, no thistle growth appeared until May 6, 2012. Proso millet was planted on this field with only one small patch of thistle appearing above the millet canopy at harvest. Other thistle patches remained below the millet canopy and many were infected with gall flies. I would deem Canada thistle control to be significant. Because of the dry weather in 2012, I expect to note better Canada thistle control in 2013.

Forage soybean cover crop trial:

• Plot size: 4 acres
• Previous crop: triticale/hairy vetch green manure.
• Tillage: Double disk poor stand of triticale/hairy vetch June 1st.
• Seeding: June 24, using IH 100 drill sowed about 85 lbs./acre or 10 seeds per square foot of inoculated Forage soybeans from American Organic Seeds
• Incorporation: July 30 at 1 to 1 1/2 feet tall.

Other cover crops planted at the same time germed and emerged in fine shape, but not the soybeans. Even though seemingly planted into moisture, emergence was slow and spotty. At incorporation the stand was less than 5 plants per square foot. Previous experience with soybeans was minimal, but it seems very good moisture is necessary for soybeans to be of much value in a drier situation.

In 2011 we mixed the sudan and soybeans together, and even with the less dense stand of sudan, the forage soybeans made little growth. Thus, planting them alone to see how they would do.

Sorghum variety screening, pearl millet trial:

Planted (with a hand planter with plate)on June 6 were 19 new white sorghum accessions from Matt Kolding, the bulked accessions from 2011 harvest of white sorghum from Matt Kolding, a pearl millet multi-line from Matt Kolding, and Kaoling, a red sorghum we have been experimenting with for several years.

The new accessions of white sorghum germed poorly, but those that did made good growth, on the whole a little later in maturity with considerably more variability than the 2011 lines, height 3 to 4 feet at maturity. One accession was only 1 foot tall on August 6 and showed no sign of heading. Two lines produced no mature seed. Heads were large with large seeds, with potential for high yield. Heads were cut by hand after being frost killed and dried A bulked 21 pounds of cleaned weight obtained.

A 100 ft. row of the bulked 2011 harvest was planted as above, along side the new accessions in a row 6 feet apart. Emergence was very good. They began to shoot in mid-July and were completed by August 6. Height at maturity was about 4 1/2 feet. One plant grew to about 6 feet and was an obvious cross with Kaoling from 2011. This head was harvested separate, the remainder bulked. The 48 cleaned weight pounds from this row translates into an impressive 6000+ pounds per acre.

A 200 ft. row of Kaoling was planted on May 14 away from the white sorghum to prevent crossing. Pole beans (Hidatsa Shield and Blue Lake) were planted with the Kaoling in the same row to test whether the taller (6 to 8 feet) Kaoling would provide adequate support for the beans as a companion crop. It provided mostly good support for the beans, however, in drier areas of the row the Kaoling wilted enough in the drought to cause some plants to bend over. We will continue to experiment with seeding rates in the future. 27 clean pounds were harvested from this row. Three plants which were obvious crosses with the white sorghum were kept separate. Note that the Kaoling is quite cold soil tolerant, is taller and thinner stemmed, has narrower leaves spaced further apart, perhaps has less drought tolerance, and has smaller seed heads than the white sorghums from Matt Kolding.

A 4 ft. row of pearl millet was planted on June 6. By August 6 this population varied in height from 3 to 5 1/2 feet, some completing flowering, other just beginning, some just heading. Heads are up to 8 inches long. Bees love pearl millet pollen. It is very heat and drought tolerant. Perhaps a selection from this population could be made for maturity and good yield for this latitude. I have no idea, however, what constitutes high quality pearl millet seed. About 1 1/2 pounds of seed was obtained.

Please contact David Podoll if you are interested in obtaining for experiment or increasing the white or red sorghums or pearl millet: 701-883-4429 [email protected]


Participation Summary
Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.