From: Curtis D. Fountain
Agricultural Extension Agent – Field Crops
While most grain sorghum plantings will follow wheat harvest, this is being sent now for some May plantings.
Herbicide Rotation Restrictions
Herbicide use prior to sorghum plantings should be considered. Common herbicides with significant rotation restrictions for sorghum are Cadre (18 months), Classic (12 months), Osprey (10 months), and Staple (18 months). Note attached NCSU Sorghum 2012 Test Report & Recommendations Table 6 (page 25) for additional information.
High yields can be obtained from May 1 – July 1 planting dates. Soils should be 60-65 degrees F at 10:00 a.m. at a 2-inch depth 3 consecutive days for plantings. Warm soils promote rapid germination, emergence, and seedling growth.
There is concern that higher 2013 US grain sorghum plantings will result in seed shortages. As a result, 2012 NC, VA, and SC variety tests are shown. Note attached NCSU Sorghum 2012 Test Report & Recommendations Table 1 (page 4) for NC data. Visit http://pubs.ext.vt.edu/AREC/
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) & 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 layby nitrogen and layby herbicide opportunities.
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.