With advances in corn genetics to tolerate dry conditions, and the adoption of glyphosate resistant corn, many farmers may ask, “why should I grow grain sorghum?” Grain sorghum, or milo, has long been known as a drought tolerant crop. Sorghum shares the water use efficiency of other warm-season grass crops. While sorghum requires about 6.5” of moisture to get to the point where it will produce grain, the production with additional moisture is very efficient; accumulating about 500 lbs of grain or about 9 bushels per acre-inch once that point is reached. Sorghum is also well known to be beneficial in maintaining high populations of pheasants, and the seed cost is low compared to corn.
Sorghum in a crop rotation can provide significant benefits. There is no perfect or right crop rotation, but each crop a producer can work into their production system offers flexibility of intensity and diversity, which especially helps no-till production systems approach stable and sustainable profitability. At least three crop types (grass vs broadleaf and cool season vs warm season) and long intervals of 2 – 4 years are needed to break some of the disease, weed and insect cycles. For much of South Dakota, sorghum is a viable option.
Corn and sorghum are both warm season grass crops, so including both crops in a rotation may not appear to add diversity. The reality is that there is some difference in planting date, some variation in herbicide options, and sorghum offers both disease and insect pest benefits.
In the disease arena, one of the pathogens that can seriously plague corn producers is Goss’ Wilt, a bacterial disease. Fungicides offer no control for Goss’ Wilt, and their use can actually make the disease worse, through weakening the natural, protective layer on the leaf, and through killing beneficial fungi, which feed on bacteria. Bacterial Stripe and Bacterial Streak can occur on sorghum, but neither have warranted control measures, and are different organisms than Goss’ Wilt. With no pesticides effective against Goss’ Wilt in corn, control measures are limited to hybrid resistance, crop rotation and residue management. Astute no-till producers know that they need all the residue they can get, so have no interest in tilling or removing residue. Milo offers a rotational crop ahead of corn that can help control Goss’ Wilt.
Corn rootworms and corn borers are two of the insect pests that corn producers have to manage. Crop rotations that put years a field is in corn close together intensify the need to do so. Neither insect affects or can survive on sorghum, adding another benefit to including the crop in rotations.
Several of these characteristics may explain why higher corn yields have been reported at the Dakota Lakes Research Farm when the corn follows sorghum than when corn follows corn. Access Long-Term Dryland Rotation Results 1990 to 2012 from the Dakota Lakes Research Farm to compare corn versus sorghum yields in various rotations. Dwayne Beck, Manager of the Dakota Lakes Research Farm says that grain sorghum is grown at Dakota Lakes because it’s better than corn when it’s hot, when it’s dry, for catching snow, it has less insect pressure, lower seed cost and the residue is easier to seed into. Farmers operating in regions of South Dakota where sorghum is adapted, may want to consider making it part of their crop rotation if they don’t already.