Monday, November 13, 2006

Evaluating Corn Response to Sulfur by Use of Mehlich 3 in North Carolina.

David Hardy, North Carolina, Dept. of Agric., N. Carolina Dept. of Agriculture & Consumer Serv., 1040 Mail Service Ctr, Raleigh, NC 27699-1040 and Greg Hoyt, Mtn. Hort. Crops Research & Ext Center, 455 Research Dr, Fletcher, NC 28732.

Sulfur deficiency in corn (Zea mays L.) at early growth (< 0.15%) is a concern to NC growers. It is more prevalent on sandy coastal plain soil but also is seen on sandy river bottom and upland soils in the piedmont and mountain regions. Although relating soil extractable S to plant response in the field is difficult due to interactions among soil, plant, and climatic factors, over recent years, Mehlich 3 extractable sulfur of 12 mg L-1 or lower has been associated with deficiency in corn. In 2005, a soil test S recommendation (16.8 to 24 kg ha-1) for field crops was implemented statewide using the aforementioned soil measure as the critical level. To further validate the need for recommendation, experiments were conducted statewide over a range of soil types common to corn production. Treatments (4 rates of calcium sulfate to supply S at 0, 11.2, 22.4, 44.8 kg ha-1 broadcast) were arranged in a randomized complete block design with four replications. Soil samples were taken prior to study initiation and at early growth stage (V6) by depth; plant tissue samples were taken at early growth and tassel. Yield was estimated at harvest. Initial soil test levels was not 100% accurate in predicting a response in yield. Preliminary yield results show 6 of 14 sites to be responsive to sulfur applications with 16.8 to 24 lb S acre –1 achieving maximum yield at all but one location. Critical plant tissue levels ranged from 0.15% to 0.2% (V6) and 0.1% to 0.15% for the coastal plain and piedmont / mountain, respectively.