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David H. Hardy Section-Chief, Soil Testing Agronomic Division, NCDA&CS. Overview of S Management & Related Usefulness of Soil Testing. SERA 6 Meeting June 21, 2011. Ordinary superPO 4 -2 (0-20-0) not used 12% S Higher yields via varieties and management = more S demand
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David H. Hardy Section-Chief, Soil Testing Agronomic Division, NCDA&CS Overview of S Management & Related Usefulness of Soil Testing SERA 6 Meeting June 21, 2011
Ordinary superPO4-2 (0-20-0) not used 12% S Higher yields via varieties and management = more S demand Cleaner air due to air quality regulation Increased Importance of Today
Sulfate Wet Deposition TrendsNADP database - current eastern NC estimate (wet + dry deposition: approx 8 lb S/ac/yr)
Subsoil where topsoil not managed 68 ppm S Subsoil where topsoil managed 138 ppm S Subsoil S Reserves Hardy MS thesis, 1983
Sulfur Deficiency Symptoms Sulfur Deficiency
Sulfur Deficiency Symptoms Sulfur Deficiency
Soil Sulfur – Corn Yellow Green corn: S-I = 30 n = 37, mean = 23
Plant Tissue Levels • Yellow corn • 0.14% S • N:S = 26 • Green corn • 0.18% S • N:S = 22
S Studies 2005 & 2006 • Validate plant response to soil S levels using M3 for both wheat and corn • Responsive and nonresponsive site • Based on surface M3 = 12 ppm • S source- pelletized gypsum • S rates- 0, 11, 22, 45 kg ha-1 • Applied broadcast after planting for corn • Split for wheat at two higher rates
S Studies 2005 & 2006 • Soil samples at study initiation and V6 • Depth A: 0 to 10 cm- NT; 0 to 15 cm- CT • Depth B: 10 to 20 cm- NT; 15 to 30 cm- CT • Plant tissue at V6 and VT • Yield
Hyde Co, Armstrong Farms, muck, 2005(only significant response was in V-6 plant tissue S)
a ab ab b Edgecombe-2, 2005 • Soil S • 0 – 9 10 – 10 20 – 11 40 –15
Greene, 2005 a a a a • Soil S • 0 – 11 10 – 13 20 – 13 40 –18
Bladen Co., 2006 a a a b • Soil S • 0 – 10 10 – 10 20 – 11 40 –10
S Studies 2005 & 2006 Overview • 2005, 1 of the 2 predicted sites responded • Greene Co. data is bothersome • 2006, 1 in 5 predicted sites responded • Weed problems, Organic soil may have mineralized S…?? • Plant nutrition improved @ V6 on both responsive and nonresponsive sites
Recommendation??Similar Quandary as Nitrogen • Highly leachable as nitrate but subsoil S • Mineralization / immobilization issue • However, possibly overlooked, unlike N • Easy to acquire value from ICP, unlike N
Current S Recommendations Soil critical level: 12 ppm = 25 S-I 15 to 25 lb per acre of S depending on soil class Know your soils Consider S fertilizer if 18+” surface sand Plant tissue sample