Sign up for email alerts of new Fluid Journal issues!
Fluid Journal : Fluid Journal 2008-2009
soluble grade of KCl (62% K2O) was used, whereas Rader evaluated a 60 percent K2O grade. Values from the Jackson method are higher than those from the Rader study. These values range from 28.6 percent higher for KCl to 141.2 percent higher for K2SO4. Potassium thiosulfate was not available when the Rader study was conducted. Seedling safety. Some references have been made using the salt index value of a fertilizer to indicate seedling safety, especially for direct placement with the seed. However, factors other than salt index values have a large influence on seedling safety in addition to the salt index value. For example, data from a recent three-year study in Minnesota by Randall and Vetsch illustrate that soil temperature has a major influence on seedling survival and yield in a starter fertilizer placement study for corn. Placement of a starter NPKS fertilizer in the seed zone produced no significant reduction in plant populations for two years of the three-year study when soil temperature was in the 56 to 60oF range, but reduced the population by 32.5 percent when the temperature was 48oF (Table 2). Soil temperature, soil moisture, soil type and the potential for free ammonia formation from urea- containing materials all influence the safety of fertilizer products placed in direct seed contact. For additional information, see the 2001 Fluid Journal article "Calculating Salt Index" at the Fluid Journal website. http://www. fluidfertilizer.com/fertilizer_article_ archive.html Dr. Clapp is agronomic consultant for Tessenderlo Kerley, Inc. Table. 2 Influence of a starter NPKS fertilizer on corn stands and yield. N-P2O5-K2O-S 2004 2005 2005 lbs/A Soil Temperature oF 56 48 60 Days to emerge 8 15 - Plant population-103/A 0-0-0-0 33.6 33.5 34.1 6-20-6-4 33.3 22.6 32.9 Yield - bu/A 0-0-0-0 181.7 166.5 209.2 6-20-6-4 198.9 145.1 215.4 Table 1. Salt Index values for K sources from Jackson and Rader methods and those reported in the Crop Protection Handbook (CPH) and Western Fertilizer Handbook (WFH) K Source Rader Jackson* CPH WFH KCl 116.3 149.6 116.2 116.3 K2SO4 46.1 111.2 42.6 46.1 KNO3 73.6 97.6 69.5 73.6 S of potash-magnesia 43.2 64.8 43.4 43.4 KTS - 63.2 68.0 64.0 *Determined by Southern Enviromental Testing, Florence, Alabama.
Fluid Journal 2005-2007