Not all wheat varieties are created equally when it comes to the amount of phosphorus they remove from the soil.
Some varieties are efficient, while others are phosphorus hogs, explains Jay Goos, soil scientist at North Dakota State University, in this instalment of the Wheat School.
So why does this matter?
“The reasons I’m concerned about this are soil test levels for phosphorus tend to be dropping, farmers are renting more land instead of owning it and we’re using crops that just export more phosphorus from the land, particularly soybeans,” he says.
With finite rock phosphate supplies, phosphorus fertilizer will likely become more expensive, possibly making P efficiency a characteristic worth considering in variety selection, he notes. (continues…)
After comparing phosphorus uptake between 47 wheat varieties grown historically in North Dakota, Goos says they noted a correlation between the rate at which a wheat variety develops and the amount of P it requires. There was an approximate factor of four in how much P was required for full initiation of the critical T1 and T2 tillers. Some varieties had near 100 percent initiation of the T1 and T2 tillers at 5 milligrams of P per pot (4 plants per pot), while others required more than 20 milligrams.
“We did not find the varieties that grow the fastest required the most phosphorus. That would be intuitive, but we have been finding the varieties that develop the fastest, the ones that require the fewest growing degree days to create a new leaf on the stem, those tend to require more phosphorus,” he explains.
As an example of how knowing the P requirements of a variety may influence farmers’ decisions, he refers to a variety known as “2375” that was popular in North Dakota in the ’90s because it was the first with any modicum of resistance to fusarium head blight.
“We know now that that variety is one of the biggest phosphate hogs in the world, and it would have been nice to know that in the ’90s when farmers were growing it,” says Goos.
He plans to begin another study looking at phosphorus efficiency in approximately 50 current and soon-to-be-released varieties this fall.