Content ID

336619

4 ways to optimize phosphorus applications

Crops require phosphorus (P), which is critical in building the structural components needed for plants to grow.

Here are four ways to ensure optimum P levels in fields.

1. Regularly test soils.

Soil test for P about every two years, says Lindsay Pease, University of Minnesota (U of M) Extension specialist in nutrient and water management.

“Generally, a postharvest soil test that mimics a plant’s ability to extract P from the soil lets you know how much P will be plant-available in the next season,” Pease says. “Plant tissue tests are also available.”

Knowing field P levels also helps reduce the possibility of environmental issues if excessive P is present. P applications exceeding what plants use can build up in the soil and potentially become a water-quality risk because of surface runoff carrying soil and P into waterways.

2. Match P applications with crop.

“When soil tests indicate your range for P is high, apply at the removal rate of your intended crop,” says Paulo Pagliari, U of M nutrient management specialist. “If the P range is on the lower end, apply about 20% to 30% more than the crop needs until your soil-test P level reaches a high level. Then, apply it at the plant removal rate. Many Extension offices have calculated crop removal rates and will gladly share the information.

“If your soil has a high clay content, with elevated iron or aluminum content, try banding the P as close to the seed as you can,” he adds. “This creates a higher P concentration band compared with broadcasting P over the entire field and maximizes plant fertilizer use.”

3. Know your soil type.

“At most, P moves through the soil slowly in the range of a few millimeters per year” says Pagliari.

“Soils with a lot of clay tend to bind P tightly, especially in the Midwest,” he says. “Aluminum and iron in more southern soils cause P retention. These bonds between soil particles and P are strong and make it difficult for P to become available again.”

P is even less mobile in topsoil. Pease recommends farmers place P by dropping it into a small trench or a small slice of soil. Light tillage can also be used to incorporate surface applications, she adds.

“For those with reduced and no-till operations, the subsurface placement may be time-consuming, but it’s better than leaving it on the surface where it’s at risk of being carried away by a rain- storm,” Pease says. “The goal is to prevent a high concentration of P in the top couple of inches of the soil. You can also try applying P at planting and pop-up fertilizers can be helpful.”

Avoid applying P to topsoil on frozen ground or if frost is imminent, says Pagliari. Instead, he advises incorporating broadcast P into the top 6 inches of soil before it freezes. This enables P to start its slow movement into the soil when rains come.

Spring applications that match crop use are ideal, he adds.

Because of runoff concerns, do not broadcast P applications without incorporation if heavy rains are predicted, adds Pagliari.

4. Let the 4Rs guide P application.

These include:

  • Right rate
  • Right source
  • Right time
  • Right placement

“University recommendations are always based on the probability of getting a good yield response and getting the most bang for your buck,” Pease says. “If your soil test indicates you won’t get much P response, reduce the application rate. Plus, that soil test will guide the rate, source, time, and placement of all remaining nutrients so your crop reaches maturity as healthy as possible.”

Read more about
Loading...

Tip of the Day

All around the shop socket tote

29559_socketcaddy If you're looking to find a way to organize, store, and carry all the heavy/bulky 1-inch impact tools around your shop, use this idea from... read more

Crop Talk

Most Recent Poll

To meet my machinery needs in the next year, I’m

holding off on buying and working with what I have
43% (33 votes)
I just want to see the responses
28% (21 votes)
looking online for deals
13% (10 votes)
sticking to my dealership
9% (7 votes)
hitting the auction market
7% (5 votes)
Total votes: 76