IS1224 Grain Sorghum Variety Selection and Planting

Grain Sorghum Variety Selection and Planting

Grain sorghum varieties may be grouped into three categories based on grain type.

Bird-Resistant or Brown-Seeded Sorghum

These contain tannins, which give the unripened grain a bitter taste. The tannin content decreases as the grain matures, and by the time grain moisture content reaches 16 to 18 percent, tannin content is low enough the grain can be fed. Brown-seeded grain sorghums are more resistant to weathering than other grain types. The seeds have high dormancy, which keeps the head from sprouting when adverse weather occurs after grain is mature. This dormancy lasts for several months. Some seeds shattered in harvesting will survive the winter and germinate in the spring, creating a weed problem in the following crop.

Tannins make bird-resistant sorghums undesirable as a feed or forage crop. Unless you have a specific market for this grain type, don't plant it.

Yellow Endosperm or Bronze-Seeded Sorghums

This type of grain is a cross between a red-seeded sorghum and a yellow-seeded sorghum. Most varieties are of this type. They are classified as yellow in the market, and the producer is not docked as he might be for brown-seeded grain. Bronze- seeded sorghums do not weather as well as do the brown-seeded type. However, you can let them field dry to 12 to 14 percent moisture content. Some bird damage and weather damage may occur. Seed dormancy is slight, and rarely do any volunteer plant problems exist. These sorghums can be used for greenchop, silage, high moisture (35-40 percent) grain and can be harvested at 20 to 25 percent grain moisture and dried. Early harvest and drying reduces weather and bird damage.

Yellow-Seeded Sorghums

This type of grain is produced when both parents of a hybrid are yellow-seeded. It makes excellent quality feed. The primary disadvantage of the yellow grain is weather damage. Grains of these varieties begin to weather earlier than other grain types. Grain will generally lose quality in a relatively short period of time after grain moisture reaches 12 to 14 percent. For consistently high grain quality, you must harvest at 18 to 20 percent grain moisture, or higher, and dry. You may use yellow-seeded sorghums in the same ways as the bronze-seeded sorghum.

Besides grain type, there are several factors to consider in selecting a variety. Yield is foremost. Periodic variety trials are conducted by the Mississippi Agricultural and Forestry Experiment Station. Results of these trials are available from the Experiment Station or from your state or county Extension Service office. Since yields vary from year to year, averages over three or more years are better indicators of variety performance than one-year results. Sorghum varieties differ in maturity. This is caused by inherited differences in response to light and temperature. Many of the varieties grown in Mississippi are intermediate maturing, usually flowering 60 to 70 days after emergence. Varieties are available that will flower in less time, but as a rule they do not yield as well. Later flowering varieties are also available. Neither early nor late-maturing varieties are as well adapted to most of Mississippi as are the intermediate flowering varieties. You might consider limited acreages of these varieties if you need to spread the harvest over a longer period of time.

Very few leaf diseases are serious problems. Stalk and head diseases present the major problems. Anthracnose is a major, devastating disease. You must have anthracnose resistance to get optimum yields.

Charcoal rot is also a problem following periods of hot, dry weather during plant development. Resistance varies according to variety. Most sorghums have partial resistance or tolerance rather than resistance.

The Fusarium complex affects roots, stalks, and heads of grain sorghum. Fusarium stalk rot and head blight can cause severe yield losses. The stalk rot is usually accompanied by extensive root damage. Fusarium stalk rot is more of a problem when cool, wet weather follows hot, dry weather. Maximum tillage, high nitrogen fertilization, high plant populations, and continuous cropping to sorghum seem to increase fusarium problems.

Fusarium head blight affects the upper stalk and head. Grain may be light and/or "moldy." Good cultural practices are the best ways to minimize most disease problems.

Seed at rates of 4 to 6 pounds of seeds per acre for most varieties. Seed size varies, and the best way to determine rates is to plant a certain number of seeds per foot of row. Without irrigating, you should seed sorghum at the rate of 65,000 to 85,000 seeds per acre. Seeds per foot of row should be as follows:

Row width (inches)	Seed/foot of row
20	3 to 4
30	4 to 5
36 to 38	5 to 6
40	6 to 7

These seeding rates assume that 80 percent of the seeds planted will produce plants. Final plant populations for nonirrigated sorghum should be 50,000 to 70,000 plants per acre. Irrigated sorghum plant populations should be 70,000 to 90,000 plants per acre. Where soils are drought prone, such as sandy and/or badly eroded soils, final plant populations should be 30,000 to 35,000 per acre.

Planting depth should be 1 to 2 inches. When soils are cool (60 degrees Fahrenheit), 3/4 to 1 inch deep is adequate; in warm soils, 1-1/2 inches deep may be necessary. Do not plant more than 2 inches deep.

Row width may vary from 20 to 40 inches. In most tests, narrow rows (20 to 30 inches) produce slightly higher yields (400 to 500 pounds of grain per acre) than 38- to 40-inch rows. From a management standpoint, it is advisable to use the same row spacing for sorghum that you are using for other crops.

Planting grain sorghum with a grain drill or broadcast increases management problems. Diseases also tend to be more of a problem in sorghum planted this way. It is difficult to keep seeding rates at desirable levels. Postemergence herbicides are limited to early applications of 2,4-D or Banvel. If seeding rates are too high, lodging will be much more of a problem. If you must plant sorghum with a grain drill, stop up every other discharge spout. This increases row spacing to 14 to 20 inches, which is much better than 7- to 10-inch spacings.

Originally prepared by Charles C. Baskin, Ph.D., retired Extension Agronomist. Distributed by E. Lamar Kimbrough, Ph.D., Extension Agronomist, and Alan Blaine, Extension Agronomist

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Information Sheet 1224
Extension Service of Mississippi State University, cooperating with U.S. Department of Agriculture. Published in furtherance of Acts of Congress, May 8 and June 30, 1914. Ronald A. Brown, Director

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