Sudangrass & Sorghum

by Joann Burch

Sudangrass is a tall annual grass. It probably originated in Egypt or Africa. It is believed to be the wild original form of the cultivated sorghums. The two cross readily when planted near each other. Sudangrass is used for feed for stock in a variety of ways and as a late Summer crop. The root system is very good for breaking up the soil and keeping it loose. Sorghum, as we shall see, is used for a variety of purposes.

Sorghum probably originated in tropical Africa, with India following shortly behind. There is evidence it was cultivated in the Orient long before the beginning of the Christian era. The first Sorghum introduced into the U.S. was the ‘broom-corn’ in colonial times. Sorghums were widely distributed by the U.S. Patent office in 1857. Since that time the Dept. of Agriculture has introduced numerous varieties from all parts of the world as the semi-arid regions developed. Sudangrass was introduced in 1909.

Sorghums separate into two groups. The perennials like Johnson-grass and the annuals like Sudangrass. In general, annual sorghums grow three to fifteen feet in height with erect, stout (½ – 2½ inch), jointed stems. Sudangrass grows 4 to 8 feet tall.

The cultivated sorghums may be divided into five groups: Broom-corn, Shallu, Durra, Sorghum, and Kafir. However, in the U.S. there are three classes for general use. The most common are the grain sorghums. They grow well in areas too dry or where corn does not do well. Sweet sorghum molasses is most popular, but it may be used for feed as well. Of course, broom-corn is dry and used mostly for its broom straw.

The two classes of sudangrass are sorghum-sudangrass hybrid varieties and sudangrass. Between the two there are about forty varieties. In the western states, the California and Washington Agricultural Experiment Stations found the variety Piper sudangrass to equal or exceed other varieties in most of their tests. It would probably be most beneficial to check with your own agriculture department before deciding on a variety.

Sorghum does not require the fertilizer that corn does. The PH should be about neutral – 6.5 to 7. It takes about 5 tons of manure per acre for sweet sorghum. Tankage and cottonseed meal are good fertilizers too. Sudangrass needs nitrogen, potash, and phosphorus.

Good seedbed preparation is essential. Irrigation should be done before preparing the seedbed. Both sorghum and sudangrass should be planted after the soil is warm. The seed can be broadcast, drilled, or cultivated in rows. If you are cultivating with horses, the rows should not be narrower than 28 inches. Forty-two or forty-four inches is the usual distance. Seed may be planted from May 1 to August 1 on irrigated land and no later than June 1 on non-irrigated land. In my research, I have found discrepancies in the amount of seed to plant per acre, I hesitate to make a statement. There again, it would be best to check with your county agent or local seed dealer. One thing to keep in mind; your purpose for seeding the crop. Thick seeding produces finer stems and more leaves. Naturally, the irrigable land could handle more plants per acre. If you do irrigate, the ditching should be done before seeding. Closer spacings are preferred on sandy soil. Sprinkler irrigation is okay if the crop is to be pastured, but ditching is recommended if the crop is grown for hay, silage, or seeds because of the height of the crop.

Sudangrass lacks rootstocks so it never becomes troublesome as a weed. The stems are leafy, perfectly erect and seldom lodging. The sugar content is only enough to give a sweetish taste. The panicle is loose and open, pyramidal is form and 6 to 18 inches long.

When growing sorghum or sudangrass for seed they should be planted in rows. Like corn they are wind pollinated. If different varieties are grown close together they can cross freely. Bagging the heads before the stigmas are exposed would prevent cross-pollination. The bags should be opened as soon as the seeds have set to prevent molding. Thinner seeding is better for seed production. It is difficult to make a distinction between the two seeds if they are mixed together.

Selection for sweet sorghums should be for sweetness, juiciness, disease resistance, leafiness, and erectness. The tallest and coursest varieties are preferred with yield as a secondary matter.

Among the grain-producing sorghums, yield is top preference. The other points should be considered, especially for dual-purpose.

Sudangrass as a hay crop is preferred over the other sorghums. It can be fed to all kinds of livestock without injury to them. It can be readily cured into hay because of the finer stems. Though sudangrass hay is superior to the other millets, it should be used only as a roughage. Proteins and concentrates should supplement the hay. Sudangrass should be cut for hay in the full bloom to soft dough stage. The length of the season and moisture must be taken into consideration, although there is little deterioration if the grass has to stand longer. The hay cures readily in bundles if it is cut with a binder.

Sudangrass matures well when grown together with cowpeas and soybeans. It prevents the legume leaves from matting together during curing. Sorghums and sudangrass are rapid growers so in some areas two and possibly three cuttings may be harvested.

Although corn is the preferred silage, forage and grain sorghums are used. Forage sorghum is very high yielding. Forage sorghum seems to contain excess water and acid which cuts down the palatability and nutrition. Grain sorghum silage is between corn silage and forage sorghum silage in palatability. It is superior to both because of its higher dry matter content making it more nutritive. The grain sorghum is usually low yielding.

IMPORTANT NOTE. Sudangrass and sorghums are well known for containing large amounts of prussic acid or hydrocyanic acid (HCN). However, this disappears when cured. Care should be taken to not pasture sheep and cattle on it until it reaches 18 to 24 inches of normal growth. It does make excellent pasture for hogs as HCN doesn’t seem to bother them. It should noted too, cattle and sheep may bloat if turned on sorghum pasture when the plants are wet or the animals are hungry.

Fencing for a rotational grazing system and use of certified seed cuts down the danger of poisoning. Washington State University found Piper sudangrass to be low in hydrocyanic acid.

After sudangrass had been pastured for one week or after a frost it should be left for three to four weeks for regrowth between grazing periods until fall frost. Hence, the rotation of fields. Remove the stock if new shoots appear. If care is taken, cattle do well grazing on sudangrass. At the Washington Experiment Station they produced 300 pounds of beef per acre during the growing season. Steers gained 1¾ pounds per day.

Crop rotations, sanitation, and the use of disease-resistant varieties help prevent or combat diseases. Downy mildew has been a problem with sudangrass in some areas. It would then contaminate other sorghums. Damage hasn’t been a big problem. Disease resistant varieties have kept pests and diseases to a minimum.

A Ciba – Geigy systemic fungicide seed dressing called ‘Apron’ for control of systemic downy mildews and diseases caused by soil-borne Pythium and Phytopthora has been given the okay by the Environmental Protection Agency. At this time it may only be used by commercial seed treaters.

Sorghum and sudangrass are very rapid growers so they are excellent for quick organic matter production. Except for very wet soils, they tolerate all others very well. These non-legumes are grown in all parts of the U.S. There have been some varieties found that will clean salt from the soil, therefore, making land productive that was considered waste before.