“At current P prices,
I will be happy if farmers can continue
to just seedplace 20
to 25 pounds per acre of P2O5.”
Phil Needham says in the other article on page 6 that deep banding of phosphorus worked for some farmers in Kentucky, but he says it’s probably not an option for zero-tillers in Western Canada. Then again, if phosphorus is deficient at lower depths, would it be worthwhile getting some phosphorus down there? I asked Lyle Cowell, Viterra agronomist in Tisdale, Sask., and Rigas Karamanos, agronomy manager with Viterra, for their thoughts.
Cowell doubts the value of this practice from either a practical or scientific perspective. “The cost and effort to deep band phosphorus would provide negligible rewards to the farmer,” he says. “At current P prices, I will be happy if farmers can continue to just seedplace 20 to 25 pounds per acre of P2O5.”
Karamanos agrees. “Deep banding phosphorus is not a good idea,” he says.
Karamanos, along with John Harapiak and Norm Flore of the old Westco Fertilizers, wrote a scientific paper in 2007 to highlight the findings from a 12-year experiment in fertilizer placement in barley. In a cool spring, seed placed phosphate produced the best yield. In a warm spring, banded phosphate produced the best yield — but this was for shallow bands (three to four inches deep) only. Placement of phosphate in a band six to seven inches deep was never the best option for barley. (It can work well for canola in dry spring conditions, the study noted.)
So does that mean you should put some phosphate in the seedrow and some in the band? Yes, for many fields that will work. “Banding of phosphate in dual N-P bands can be effective, especially in situations where fields have had a significant history of fertilizer P application. However, if a field is quite responsive to P fertilization, all or at least some of the P should be applied directly in the seedrow,” the study says.
The report also made this statement reinforcing the important of seed-placed phosphate: “Flaten and Racz (1985)…concluded that banding urea together with monammonium phosphate (MAP) at the time of planting did not produce yields that were greater than those of banding urea and seedrow placing MAP.” In other words, if it’s a choice between banding and seedplaced phosphate, go with seed placed. If you have the capability to split the application, go for it.
ONE WARNING ABOUT MIXING P AND N IN A BAND
The Karamanos, Harapiak and Flore report notes that high nitrogen rates can interfere with phosphate uptake when both nutrients are in the same band. With a 12-inch spacing between bands, a urea rate of 80 pounds per acre of actual N starts to interfere with P uptake. With narrower spacing, which means more bands per acre and lower rates per band, you can apply more nitrogen per acre before you see interference.
The study also says ammonium nitrate is safer than urea in terms of phosphate uptake interference.
Jay Whetter is editor of Grainews