Grain Sorghum

— Written By Curtis Fountain and last updated by
To:  Duplin Co. Grain Sorghum Interests

From:  Curtis D. Fountain

Agricultural Extension Agent – Field Crops

Following 2013-14 wheat harvest, grain sorghum will be planted primarily where soybeans are not expected to be profitable. These situations include continuous soybean or continuous wheat/soybean cropping, past soybean palmer amaranth management failures, and high deer populations/feeding pressure.

Herbicide Rotation Restrictions

Herbicide use prior to sorghum plantings should be considered. Common herbicides with significant rotation restrictions for grain sorghum are Cadre (18 months), Classic (12 months), Osprey (10 months), and Staple (18 months). Click here for NCSU Sorghum 2012 Test Report & Recommendations Table 6 (page 25) for additional information.

Planting Dates

High yields can be obtained from May 1 – July 1 planting dates.

Varieties

Click here for 2013 Tri-State Grain Sorghum Performance Tests. NCSU variety tests results can be found on pages 40-50.

If planting sorghum after sorghum or sorghum after corn, select sorghum varieties with high resistance to anthracnose. Select medium or late maturing varieties for June plantings. Select medium maturing varieties for July plantings. Early maturing varieties typically do not perform well in the Southeastern US.

Row Spacings/Plant Populations
NCSU Sorghum 2012 Test Report & Recommendations (pages 7-9) reveals narrow rows (7.5-inches) had the highest yields at 120,000 plants/acre, 160,000 plants/acre, and 300,000 plants/acre. Yield did not differ significantly at these 3 plant populations. Please remember the following:  1) the 3 test sites soil types were loams (not sands), and 2) adequate soil water was available during the head/pollination/grain fill period. For both 15-inch and 30-inch row spacings, 80,000 plants/acre produced optimal yields. Remember “wide rows” offer lay-by nitrogen and lay-by herbicide opportunities.
Assuming 15-inch rows 80% emergence, 100,000 seeds/acre (2.9 seeds/row foot) would result in 80,000 plants/acre. Assuming 30-inch rows 80% emergence, 100,000 seeds/acre (5.7 seeds/row foot) would result in 80,000 plants/acre. Assuming 38-inch rows 80% emergence, 100,000 seeds/acre (7.3 seeds/row foot) would result in 80,000 plants/acre.
Seed Depth
Seeds should be planted 1-2 inches deep, depending on soil moisture and surface residue. Do not plant seeds deeper than 2 inches.
Fertilization
NCDA&CS grain sorghum (milo) target pH, P2O5, and K2O recommendations are the same as corn (grain), wheat, and soybeans. Utilize your soil test report for grain sorghum nutrient recommendations. In the absence of a soil test, apply 10-20 lbs/acre of P2O5 and 50-70 lbs/acre of K2O. 20 lbs/acre of sulfur are recommended for sandy soil plantings.
1 1/2 pounds of nitrogen per expected bushel of sorghum is recommended. 60-80 bushels/acre of sorghum have been common on Duplin County marginal, sandy soils. Apply 25% of the nitrogen at planting and the remainder at lay-by. Lay-by nitrogen should be applied when plants are 10-12 inches tall.

Weed Management
NCSU Sorghum 2012 Test Report & Recommendations Tables 3 & 4 (pages 12-14) note preplant, preemergence, postemergence, postemergence-directed, and postemergence-hooded herbicide options. Start clean! A common herbicide program has consisted of a preemergence herbicide such as Bicep II Magnum (Dual + atrazine) or Lariat (alachlor + atrazine). When sorghum is 6-8 inches tall, atrazine + 2,4-D amine are sprayed postemergence-overtop. Do not exceed 2.5 lbs active ingredient of atrazine per acre per season. When sorghum is at least 15 inches tall (2-4 inch weeds/grasses), Linex can be sprayed postemergence-directed (no higher than the lower 3 inches of the stalk). When sorghum is at least 15 inches tall (4+ inch weeds/grasses), Linex + Gramoxone can be sprayed postemergence-hooded.

Remember there are other herbicide options. Consider weeds/grasses present, herbicide costs, and herbicide rotation restrictions.

Thanks.
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Extension Agent (Agriculture – Field Crops)
NC State University, College of Agriculture & Life Sciences
N.C. Cooperative Extension  —  Duplin County Center
PO Box 949  Kenansville, NC  28349
Phone:  910-296-2143      Fax:  910-296-2191