Grain Sorghum – Stand Issues And Replant Considerations

DR. ANGELA MCCLURE

JACKSON, TENN.
   Dry weather following sorghum planting is causing inadequate preemergence herbicide activation and thin stands, and I have gotten a number of calls requesting info on the recommended minimum stand in replant situations. Planting thick enough to ensure final stands of 60 to 70 thousand plants per acre (ppa)does a couple of things for us 1) promotes slightly faster canopy closure vs thin stands regardless of row spacing, 2) minimizes damage from sugarcane aphid which can be more damaging in thin stands because there is less biomass for aphid populations to feed on 3) is low enough (but not too low) to minimize plant competition for water under drought conditions which may in turn reduce stalk rots compared to fields planted to higher densities.
   University of Arkansas data shows a 10 to 15 bushel reduction across three varieties with a final stand of 40 thousand ppa compared to 60 thousand plants ppa on wide (38″) rows. Mississippi State data suggests a dryland sorghum stand in the 40 to 70 thousand range is still adequate as long as it is uniform and clean with good residual weed control.  Where stands are not very uniform, thin (much below 60 thousand ppa), and when grass is emerging with the sorghum due to lack of activating rainfall on preemergence products, I would consider killing the stand and starting over. It is difficult to control grasses in sorghum, especially when weeds outgrow the crop. Sorghum is much less competitive than corn with respect to grass weeds, there are few good POST herbicide options, and at this point we still have time to get a good yielding crop if sorghum is replanted in mid May. ∆
   DR. ANGELA MCCLURE: Extension Corn and Soybean Specialist, University of Tennessee