Although much of the sorghum in the U.S. is grown under dryland production practices, growers with irrigation are seeing the value of including sorghum in their cropping system. Sorghum’s ability to wait for water makes it a desirable partner in a field where irrigation is being shared with other crops. This ability to wait on its next drink gives irrigation managers the flexibility to divert water to each crop during critical growth stages.
In the age of advanced technology, harnessing its potential for precision irrigation has never been greater with an abundance of information available to know when, where and how much water to apply. The integration of smart irrigation systems, soil moisture sensors and remote monitoring tools empowers farmers to make data-driven decisions and optimize water usage.
As stewards of the land, sorghum farmers recognize the importance of employing efficient irrigation techniques. Embracing technologies such as drip irrigation and highly efficient center pivot systems allow farmers to maximize water delivery to the sorghum roots and minimize waste.
Monitoring soil moisture levels is a valuable tool for water management. Utilizing soil probes and sensors enables producers to gauge irrigation requirements accurately, preventing under or over-watering. This approach not only conserves water but also promotes healthy root development and overall crop vigor.
Deficit irrigation represents a viable strategy for sorghum production. By strategically applying water during specific growth stages, sorghum can tolerate controlled water stress without significant yield reduction. Managing irrigation judiciously during less sensitive growth periods optimizes water usage while maintaining satisfactory yields.
As advanced as irrigation technology has become, there is still basic information that growers need to know to maximize water use efficiency. It starts with knowing your soil and its water holding capacity. Soil texture, along with percent organic matter largely determines water holding capacity, and more importantly, how much of the water is available to the plant.
For example, a sandy soil with one percent organic matter typically holds 1 inch of water per foot compared to a silty clay loam soil with 3 percent organic matter that holds 2.2 inches of water per foot. Many growers know their soil water holding capacity in their top 1 foot of soil, but it is also important to know it deeper in the soil profile. By knowing the water holding capacity at different zones in the profile, irrigation managers can better utilize the information being provided by soil moisture sensors and other technology tools. Soil series maps (Web Soil Survey) from NRSC can provide estimates of soil profile texture as an alternative to deep soil profile mapping of fields.
On average, sorghum will consume approximately 20-24 inches of water during its growth cycle for maximum yield. How much water is needed by sorghum at any particular growth stage is greatly influenced by its environment. Much more water is needed for sorghum grown near Phoenix, Arizona, compared to Hays, Kansas, and variation in water use at any given location can vary greatly from year to year, and even week to week. It is crucial for growers to know their local daily reference evapotranspiration (ETo), which is the estimated water use of cool-season grass. This number is now available for most regions through government agencies, universities and private industry. Once the ETo is known sorghum and other crops water use can be estimated. This information, coupled with knowledge of soil water availability, will go a long way in implementing water-efficient strategies to minimize waste and maximize water use efficiency.
When to irrigate to maximize yield and water use efficiency is the goal of most growers. In order to take full advantage of each inch of water, it is helpful to know key growth stages in sorghum. Uniform stand establishment is important. If needed, irrigation should be applied to ensure stand establishment. The most critical time to consider is approximately 30-40 days after emergence. This is when the formation of the sorghum head is initiated and when the potential number of kernels per head is determined. If moisture stress occurs at this time, head size will be small and grain numbers per head will be reduced.
The next and most important stage of development is at boot, which is just before the head emerges at the top of the plant prior to blooming and grain set. Many trials over the years have shown that adequate soil water at this time will greatly enhance yield. Avoiding water stress at this time can easily add 500 pounds of additional yield and could add as much as 800 pounds.
Although not as critical as the aforementioned stages, avoiding water stress during the grain fill period—especially during soft dough—can add test weight to the final yield. A good time to irrigate is just as the grain is beginning to turn from green to its final color.
Irrigation is unlikely to add to yield once the grain has reached hard dough. At this stage, as much as 2 inches of water can still be used by the crop. If conditions are dry, irrigation at this time can improve stalk strength which reduces lodging and increases harvest efficiency. As long as the plant remains green, it requires some water to maintain stalk integrity.
For maximizing sorghum yields, soil water should be maintained above 50 percent available water to a soil depth of three feet. However, grain sorghum yields will normally not be reduced as long as soil-available water stays above 30-40 percent.
Monitoring soil moisture, weather conditions and crop growth stage empowers growers to identify the ideal time to apply irrigation, optimize water usage and enhance yields.
Sorghum farmers possess the knowledge, experience and dedication to cultivate this versatile crop sustainably. By integrating water-wise practices, employing efficient irrigation techniques, leveraging technology and participating in collaborative initiatives, producers can nurture prosperous and sustainable sorghum production.
As farmers continue to innovate, adapt and champion water-wise sorghum farming practices, it ensures a prosperous future for farms and communities while cultivating a sustainable water future for generations to come.
This story originally appeared in the Summer 2023 Issue of Sorghum Grower magazine.