What’s New with P Fertilizer Use?
A six-year study at three locations for continuous corn response to differing phosphorus (P) application practices was completed in 2016. The locations were at the university's Haskell Ag Lab, the Eastern Nebraska Research and Education Center near Mead, and the West Central Research and Education Center at North Platte. All sites had initial Bray 1 P of less than 10 ppm. The results have not yet been fully interpreted for Extension purposes. The results show, however, that
- annual application of P at rates equal to the P removed in the previous harvest when Bray-1 P is less than 20 ppm has a slightly better profit opportunity compared with the current UNL recommendation, and
- maintaining Bray-1 P at 25 or 35 ppm resulted in less profit than the UNL recommendation.
For other crops, available research-based information does not challenge existing UNL recommendations as reported in the Nebraska Extension publication, Nutrient Management for Agronomic Crops of Nebraska (EC155) if the farmer’s primary objective is profit optimization. We realize that:
- some producers give priority to objectives other than maximization of profit which may justify their maintenance of very high soil test P levels, and
- some advisors recommend P rates in excess of UNL recommendations.
Available research-based information indicates that these higher rates reduce profit potential.