The Indiana Prairie Farmer carries Crops Corner and Hoosier Bug beat columns each month. If you don't have hard copies, you can find past issues at this site. Go to the home page, then to 'more Prairie Farmer' in the upper right hand corner, then to magazines online. You will see each magazine from the past several months displayed page by page, in full color.
The people who write those columns are crops consultants and seed specialists. All are members of the Indiana Certified Crops Advisors group. Here's more discussion of the value and limitations of pop-up fertilizer. Look for the conclusion in a special story in the March issue of Indiana Prairie Farmer.
"If your fertilizer dealer is telling you that you need to use a liquid pop-up starter on your corn and not spread any potash, I hope that your potassium levels are at an optimum level already," says Darrell Shemwell, one of the current columnists. He is an agronomist with the Posey County Co-op, based in Poseyville.
"Most pop-up fertilizers are just what they are called: something to get the plant out of the ground and used in addition to a good fertilizer program," he adds. "Pop-up fertilizer formulations are high in phosphate and low in nitrogen and potassium. Some examples are 8-24-4, 6-24-6, or 9-18-9."
The high phosphate content is usually not harmful because it doesn't affect the roots and germinating seedlings like nitrogen or potassium, or the combination of nitrogen and potassium. Phosphate is the nutrient that helps guard against purpling and stunted growth during cool, wet seasons in the early stages of the plant's life.
"When using a liquid fertilizer as a pop-up in furrow, you need to be aware of the salt content being used because it can decrease seed germination or cause seedling injury," Shemwell reports. "You also need to know what formulation of potassium is used in the product."
Non-chloride potassium, such as potassium hydroxide, potassium thio-sulfate and potassium carbonate are seed-safe because they have a lower salt index than a potassium chloride formulation, the agronomist explains.
"There are people who will tell you anything to make a sale, so you need to be knowledgeable about what you are buying," he emphasizes. "Using a pop-up in-furrow is a great practice, but does not replace a well-managed soil fertility program."