In our last edition of Strip-Till Strategies, I shared some perspectives on best practices and precautions for building phosphorus levels in strip-till.
We also asked our readers to share their experiences and advice on how they manage phosphorus in strip-tilled fields. Based on the feedback we received, it seemed worth revisiting the topic here.
George Rehm, a retired nutrient management specialist with the University of Minnesota Extension, spent several years researching fertilizer management strategies in conservation tillage systems, including strip-till. His studies revealed that repeated banded applications of phosphate fertilizers or potash in the strip never had a negative impact on yields.
While Rehm admits that repeated applications could raise concerns about accurate soil sampling results, his research revealed a way to get more reliable soil readings.
“If the soil core is collected 6 inches to the side of the row and 6 inches deep, this produces the best picture of the relative level of the immobile nutrients,” he says.
Shifting rows 15 inches over in a 30-inch system each year isn’t something Rehm says is necessary, and could potentially diminish yields, especially if the farmer is in a controlled-traffic system. By moving the row 15 inches each year, this places a row where equipment wheels ran the previous growing season.
Rehm admits that strip-tilling continuous corn can more rapidly deplete phosphorus levels in the soil, but a reliable residue management strategy that helps preserve in-ground nutrients should offset the need to move rows each year.
“It can be managed. There is equipment that will move the residue to the center of the row, then farmers can plant where there was a row of corn last year,” he says.
Another consideration for strip-tillers when assessing phosphorus needs is the prevalence of mycorrhizal fungi that help organically “move” banded phosphorus and make it more available to plants when needed.
This is something Mazzepa, Minn., strip-tillers Rod and Rick Sommerfield took note of on their 500-acre operation — and one of the reasons they stopped broadcasting phosphorus-based fertilizers nearly 40 years ago.
“We’ve seen research which showed that in some cases, sample plots with mycorrhizal fungi needed one-fifth as much phosphorus to achieve the same yield as those without,” the Sommerfields say. “Placing phosphorus down where it cannot erode eliminates loss to the environment.”
As we’ve noted in the past, strip-tillers don’t want to see nutrients go to waste and hopefully, you are finding a successful and efficient method to maintain or replenish your phosphorus levels.
We’d still like to hear more about your approach to storing phosphorus in strip-till. Share your thoughts by calling me at (262) 782-4480, ext. 441, or send me an e-mail at jzemlicka@lesspub.com.
