For many producers, it has been several years or, in some instances, decades since they last grew grain sorghum. During the county production meeting circuit in Arkansas this winter, one of the most common comments was, “I grew grain sorghum back in the mid 1980’s but not since – has anything changed?”
My answer is YES. There are lots of new items to consider, but the basics still apply. Here are several factors that producers need to consider this spring to get grain sorghum off to a good start and on its way to making a high yielding and economical crop.
Factor 1: Herbicide Carryover
The first and foremost item to consider in my book is what residual herbicides were applied to the field last year. In the fight against glyphosate tolerant pigweeds, overlapping residual herbicides seems to be the solution. However some of these herbicides can carryover and injure grain sorghum the following year.
Herbicides containing fomesafen (flexstar, Reflex, etc) have a 10 month plant back interval for grain sorghum. We have seen injury when grain sorghum is planted sooner than 10 months. Other herbicides such as Classic and Newpath (Clearfield rice) could also be a problem. Consult the MP519 – Row Crop Herbicide Plant Back Interval Publication here to review herbicide plant back intervals.
Factor 2: Field Selection
After you have determined you don’t have a herbicide carry over concern, field selection, specifically field drainage is very important. Grain sorghum, just like corn does not like wet feet, so having adequate drainage is needed. Grain sorghum can perform well on clay, silt loams, or sandy soils if given a fighting change.
Factor 3: Hybrid Selection
Grain sorghum hybrid selection is important. There are several companies that have grain sorghum hybrids that have been tested and have performed well in the Mid-South. The table below has 2-year average yields from all testing sites:
Factor 4: Planting Date
Planting date is a critical component to successful grain sorghum production. Grain sorghum is not nearly as cold tolerant as corn, but relatively early planting is needed to maximize yields and reduce impacts of insects later in the season, including midge, head worms, sugarcane aphids. In general, there is a 4-6 week window when yields are likely to be maximized, generally during the month of April to early May.
Planting date studies at Marianna, Arkansas showed that April planting maximized yields every year during a 6-year planting date study.
Factor 5: Seed Treatments
There are several seed treatments to consider. Concep treated seed is a must. This seed safener allows s-metolachlor (Dual) to be applied with minimal risk of injury. Without the Concep seed treatment, significant injury will likely occur with preemergence applications of s-metolachlor. Nearly all seed sold in the Mid-South is Concep treated, but NOT ALL, so double check before you seed insecticide treatments such as Cruiser, Poncho, Nipsit Inside, and Gaucho (and generics) have been shown to greatly improve stands and yields in some instances. Seed insecticide treatments are recommended for grain sorghum.
Factor 6: Early-Season Weed Control
Starting off weed free is critical, so an adequate burn-down program or tillage is needed. Immediately after planting, a preemergence application of s-metolachlor herbicide should be applied to reduce early season weeds and control grasses. There are no “good” grass control options once the grass has emerged in grain sorghum, although atrazine or facet can control very small grass.
It is very important to apply s-metolachlor immediately after planting to avoid grass problems. I generally do not recommend atrazine immediately after planting, especially if planting very early. Cold wet soil is stressful enough on small grain sorghum and adding atrazine to that scenario makes it tougher.
Factor 8: Row Spacing
Grain sorghum can be successfully grown on any number of row spacings, including 38 inch wide rows. In 2014, yields greater than 160 bu/acre were realized on single 38 inch wide rows. Data from the Mid-South, in high yield environments, generally shows a very slight increase in yield from twin row 38’s compared to single 38 inch rows or from row spacing narrower than 38 inches. In lower yield environments (typically dryland) row spacing did not have an impact on grain yield. Getting grain sorghum planted correctly at the proper planting rate, and uniform seed depth (1 inch) to facilitate even emergence should be the goal regardless of row configuration.
Factor 9: Plant Population
Plant population is an important item to consider. In general for irrigated fields we recommend 75,000 plants/acre (final stand), which would be a planting rate of about 90,000 seeds/acre. This would roughly be 6-7 lbs of seed/acre (depending on seed size). For dryland fields, a final plant population of 60,000 is recommended (75,000 seeds/acre, approximately 5 lbs of seed/acre).
In plant population work that we have done under irrigation, increasing populations greater than 75,000 did not result in any greater yield and did increase the risk of late season lodging. In dryland fields, high plant populations tend to run out of water at the critical heading stage, resulting in lower yields. Grain sorghum has a tremendous ability to compensate for thin stands.
Factor 10: Early-Season Nitrogen Management
Nitrogen management should be performed similar to corn with small amount applied before or at planting (up to 1/3 of total N) and then side-dress the remainder nitrogen once the plant gets to the 5-6 leaf stage. At about the 6-leaf stage, the plant will be entering a rapid growth stage and the plant will need to have the nitrogen available at that time for optimal yields. Total nitrogen will vary on whether the crop will be irrigated and soil type, but generally ranges from 110 units of total N for non-irrigated silt loam/sandy loam fields to 160 units total N for highest yields on irrigated silt loam/sandy loam soils.
Of course there is more to growing grain sorghum than what I have listed above, but early season blunders unfortunately last the whole season. Getting the crop off to a good start is a critical first step for high yielding and profitable grain sorghum. In-season management of weed, insects, irrigation, and harvest are all essential.
