Some Helpful Hints on Growing Forage and Grain Sorghums: Do’s and Don’ts

Some Helpful Hints on Growing Forage and Grain Sorghums: Do’s and Don’ts

Adapted by Dr. Jeff Dahlberg, Director UC-ANR Kearney Agricultural Research and Extension Center

Sorghum [Sorghum bicolor (L.) Moench] is a member of the grass family, which includes grain sorghum, forage sorghum, sweet sorgos, broomcorn, and Sudangrass and it is also closely related to Johnsongrass [S. halepense], a major weed pest. Grain Sorghum is commonly referred to in California as milo, corn, and “gyp” corn. The history of grain sorghum in California dates back to 1874, when a small consignment of white and brown Durra was brought from Egypt. Planted in the interior valleys, these introductions demonstrated their ability to withstand the hot, dry summers and soon became established as a crop. The vast majority of California’s grain sorghum is grown under irrigation. According to USDA National Agricultural Statistics Service (NASS) it was planted on 7.1 million acres in the United States in 2014 and this is predominately dryland farming. The last reported planted acres in California were 2008, when 47,000 acres were planted. Grain sorghum yields in 2007 and 2008 were 85 and 95 bushels per acre, which compared to the national average of 73.2 and 65. Although there are exceptions, double-crop grain sorghum normally yields less that “full season” single-crop plantings.

It is important to understand the growth stages of sorghum as each stage represent critical timeframes for such management decisions as irrigation, insect control, and fertility. Sorghum is traditionally divided up into various maturity classes ranging from early to late. Don’t plant the wrong maturity. This is true for both grain and forages. If you plant a late maturing grain or forage sorghum, you might run into issues in the fall when you are planning to harvest the grain or forage and it might not dry down to appropriate moisture levels for harvesting. Do understand maturities and what they represent. Maturity designations are simply an estimate of when sorghum will flower, so an early maturing grain or forage hybrid will be something that might flower between 52-58 days after emergence. A late maturity might flower 62 days or later. In forages, a photoperiod sensitive or PS sorghum will not normally flower in the US until late November. So it is important to understand what type of sorghum maturity you should be planting as this will impact when you might harvest the crop. Follow your seed dealer’s recommendations for when to harvest grain or forage sorghum to maximize your grain or forage quality.

Grain sorghums are of tropical origin and reach maximum development in regions having high temperatures and relatively low humidity during the growing season, perfect for California. Experiments and observations indicate that they can be grown successfully in all interior valleys, but production has not been good in coastal regions subjected to cool ocean breezes or at elevations above 5,000 feet. Grain sorghum may be grown on a wide range of soil types. Best performance can be expected on medium-textured soils, but with good management sandy and very heavy soils can produce high yields. Sorghum is more tolerant to sodic (alkali) and saline soils than are most field crops including corn. Soils containing high levels of soluble salts can be injurious to sorghum germination and can prevent stand establishment. With proper management, many fields having these soil problems can produce satisfactory yields. Don’t plant sorghum into cool soil temperature or low pH. Optimum soil temperatures for sorghum are around 60º F and neutral to basic soils. Sorghum will not do well in low pH soils, typically below 5. Do plant sorghum when soil temperatures are consistently above 60º F and the risk of a freeze has passed.

Remember, grain and forage sorghums should not be planted like wheat or other small grains. One of the biggest mistakes farmers can make it to over plant sorghum. This will impact its’ ability to withstand drought and can have a negative impact on yields. Don’t plant using pounds per acre. Seed in sorghum varies tremendously, so understand how many seed per pound are in sorghum, which should be on the label. Seed number can range from anywhere from 12,000 to up to 18,000 seed per pound, so planting a sorghum field thinking pounds per acre can severely impact your final plant counts. Do plant using plants per acre. Follow your seed company’s recommendations and look for their targeted plants per acre suggestions as a rule of thumb. This is true for both grain and forage sorghums.

Nitrogen application is always a concern with any crop. Sorghum has been talked about a low input crop, but many farmers might mistake this as meaning that sorghum needs little or no N. For grain sorghum, fertilization requirements are similar to corn, while forage sorghums are a bit different. Do apply adequate N rates to optimize grain yields, whether you are planting dual purpose grain sorghum for forage or a hybrid grain sorghum. It takes roughly 1.2 lbs of N for every bushel of grain yield. If you put 50 lbs N down, don’t expect 150 bushel yields. Don’t put too much N down on forage sorghums. This can lead to rapid growth and potential lodging issues. According to research out of the Univ. of Arizona, approximately 125 lbs of N is sufficient for forage sorghums.