Timing and location are crucial when applying phosphorus to crops. Depending on soil type and condition, application should parallel plant needs to utilize space and tools available, advised presenter Isaac Ferrie at the 2015 Farm Journal Corn College in Heyworth, Ill.
“When we’re placing phosphorus, inches matter -- absolutely crucial. Phosphorus isn’t going to move through the soil as readily as nitrate. We can’t just put it in a band 4” to 6” away from the plant and expect the plant to find it. We want it very close so we’re hitting it right from the start since phosphorus controls growth.”
Soil often contains large amounts of phosphorous in organic form, but plants require a conversion to ortho-phosphorus. “We supplement that conversion process with commercial fertilizers. With phosphorus, timing and placement really make the difference.”
Ferrie says the right product, timing, placement and rate all help with nutrient reduction strategies, but rate ranks lowest in importance. “When we make the phosphorus we put out more efficient, we don’t have to put nearly as much on and that greatly lowers the risk of nutrient runoff.”
Over a broad range of soils, producers battle phosphorus tie-up. In high pH conditions or very low pH conditions, phosphorus becomes unavailable for uptake. “There’s no problem broadcasting phosphorus in a MAP or DAP application in the fall if the pH range is within a normal range.” Ferries typically comes back and bands a small portion of that phosphorus as a starter application at planting – putting it in 2x2 or in-furrow. “If tie-up is too high in the soil, then we don’t want to broadcast. It’s a waste of dollars and won’t become available for the plants that season. In that case, we want to band it.”