Overview of S Management & Related Usefulness of Soil Testing David H. Hardy Section-Chief, Soil Testing Agronomic Division, NCDA&CS 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 Cleaner air due to air quality regulation Increased Importance of Today

Sulfate Wet Deposition Trends NADP database - current eastern NC estimate (wet + dry deposition: approx 8 lb S/ac/yr)

IPNI 2010 Soil Summary

Subsoil S Reserves Subsoil where topsoil not managed –68 ppm S Subsoil where topsoil managed –138 ppm S Hardy MS thesis, 1983

Sulfur Deficiency Sulfur Deficiency Symptoms

Sulfur Deficiency Sulfur Deficiency Symptoms

Plants are yellow and stunted.

Soil Sulfur – Corn Yellow n = 37, mean = 23 Green corn: S-I = 30

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

Soil data for 2005 locations. Location Surface Texture Taxonomic NameInitial Soil S Depth ADepth B ----mg dm Bertieloamy sandTypic Udipsamment1520 Edgecombe-1f. sandy loamAquic Paleudult1224 Edgecombe-2*loamy sandArenic Kandiudult1312 Greene*fine sandArenic Hapludult1311 Hydemucky sandy loam Umbric Endoudalf1420 Martinf. loamy sandAquic Paleudult1614 * Predicted responsive site based on S in topsoil being ~ 12 mg dm -3 or less.

Hyde Co, Armstrong Farms, muck, 2005 (only significant response was in V-6 plant tissue S)

a b ab Edgecombe-2, 2005 Soil S 0 – 9 10 – – –15

Greene, 2005 a a a a Soil S 0 – – – –18

Bladen Co., 2006 a b a a Soil S 0 – – – –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 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