Posted on May 19, 2020
By Brent Bean, Ph.D., Sorghum Checkoff Agronomy Director
Sorghum is a reliable dryland crop under many environments, but it also can respond well to irrigation. This versatility allows sorghum to fit into many cropping systems where the availability of irrigation water may be limited. The amount of water necessary to maximize the yield of any crop depends on the specific environment where it is grown. For example, it takes a lot more water to successfully grow sorghum in Arizona than in south central Kansas or North Carolina. Daily and seasonal water demand is dependent on climate factors such as daily maximum temperature, humidity, wind speed and solar radiation.
Sorghum yield is at its best when rainfall and/or irrigation water sufficiently meets the crop’s daily water requirement. Ideally, soil water should be maintained at or greater than 50% available water to a soil depth of 3 feet. Yield of grain sorghum normally is not reduced as long as soil-available water stays above 30%-40%. The actual amount of water needed depends on soil type, with sandy soils holding less water than a silty clay loam soil.
However, growers often plant sorghum where the supply of irrigation water does not fully meet daily and seasonal water demand. When this occurs, the goal is to supplement rainfall and any stored soil water to maximize the amount of grain produced for every inch of water applied.
When irrigation water is limited, growers need to know the three critical periods in the growth and development of sorghum that most influence yield.
Once the grain has reached the hard dough stage, irrigation water added to dry fields will not contribute much to the final yield, though it can improve stalk strength, which reduces the potential for lodging and increases harvest efficiency.
For a more detailed discussion on sorghum growth stages, along with pictures, visit Growth and Development on the Crop Production page of the United Sorghum Checkoff Program website at https://www.sorghumcheckoff.com/.