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Fluid Journal : Fluid Journal 2002-2004
1 Fluid Journal Summer 2002 Dr. John G. Clapp One Good Way To Add Punch To Starters: Include Sulfur Industry agronomist says potential yield increases from adding sulfur to starters should be even more positive in the future due to a decline in atmospheric sulfur. Summary: Following passage of the Clean Air Act of 1990 the need for sulfur (S) in starters has become ever more evident because of the significant drop in sulfate (SO4) precipitated from the atmosphere. The decrease in atmospheric sulfate deposited since the Act's passage has been as high as 75 percent in some areas. Even though responses to S in starters were apparent before passage of the Clean Air Act, responses since its passage are significantly greater, pointing even more to the increased importance of using S in starters. Crop yield response to sulfur in starter fertilizers has increased because of 1) increased use of more concentrated phosphate fertilizers, 2) reduced atmos-pheric sulfur levels precipitated due to the Clean Air Act, and 3) reduced use of sulfur-containing crop protection chemicals in crops where fungicides and insecticides are needed. Phosphorus is a main component of starter fertilizers. Current high-analysis phosphate fertilizers used, such as APP, MAP, DAP, and TSP, contain very little or no sulfur as compared to SSP. Prior to the development of concentrated phosphate fertilizers, single superphosphate was used extensively as a source of phosphorus. This material also supplied a significant amount of sulfur, which was in the range of 60 to 70 percent of that of P2O5. Starter grades high in phosphate are generally recommended in order to stimulate early root development. Liquid starter grades have become popular in many commercial operations Figure 1. Influence of S and Zn on NPK starter fertilizers applied at 7 gal/A, Eastern Iowa, Paul, avg. 1983-1986. Figure 2. Influence of S on NPK starter fertilizers on dryland corn, N balanced at 150 lbs/A, 2 x 2 placement, Lamond, et al., 1999. 150 152 154 156 158 160 162 164 Check 6-18-6 6-18-6-3S-0.5Zn Yield-bu/A 80 84 88 92 96 100 104 108 Check 30-30-10 30-30-10-10S Yield-bu/A Yield-bu/A 140 150 160 170 180 190 200 210 Check 30-30 30-30- 10S Check 30-30 30-30- 10S Check 30-30 30-30- 10S Check 30-30 30-30- 10S Pioneer 3346 Pioneer 3563 De Kalb 591 De Kalb 646 Figure 3. Influence of NP starter fertilizer and NP +S starter on hybrids, Lamond and Gordon, avg. 1996-1998.
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