New Studies Show Shrinking P + K in Farmer Fields

A hand holding soil
A new DuPont Pioneer study, comprised of more than 22,000 soil samples, suggests phosphorus (P) and potassium (K) levels are deficient in a “significant” number of fields tested. The research also confirmed that P and K deficiencies hurt both yields and grain quality, according to agronomy research manager Andy Heggenstaller.

“Growers often think first of nitrogen management when they consider soil fertility decisions because of its important influence on corn production,” he says. “However, deficiencies in P and K can inhibit yields over the long term in both corn and soybeans, limiting profit potential over time.

Testing over a 12-state geography, DuPont Pioneer found P and K deficiencies in a “significant amount” of tested fields. Heggenstaller notes that many states have modified their p and K fertility recommendations and encourages farmers to stay current on the higher nutrient requirements demanded by today’s more productive hybrids and varieties.

At PotashCorp, director of agronomy Robert Mullen says his company conducted a separate state-by-state nutrient balance analysis and also found major P and K deficits. In some states, including Iowa, Minnesota, Wisconsin, Michigan and Arkansas, more than half of the samples were “below critical level” for both P and K.

Mullen says farmers can conduct a simple five-step check of their fields to get the upper hand on potential nutrient deficiencies.

1. Visual assessment. “When in the field, nutrient deficient crops can often be identified by discoloration of the crop,” he says.

2. Soil testing. Mullen recommends collecting about 10 to 15 samples from both unaffected and affected soil areas to get an accurate representation of their field.

3. Conduct a plant tissue analysis. Like diagnostic soil testing, farmers should collect samples form unaffected and affected area, Mullen says. Collect twice in the season – once early season and once midseason, he suggests.

4. Analyze historical information. “If farmers know their fields have a proven history of micronutrient issues, they can skip to step four and be prepared to apply fertilizer to deal with that issue,” Mullen says. “During this step farmers should consider that there is a chance some of their crops won’t show any symptoms, but the fields will produce yields that are lower than predicted. This is an indication of hidden hunger, which can be fixed by paying close attention to the soil test results.”

5. Prescribe corrective course of action. Hopefully, steps 1 through 4 reveal the solution needed, Mullen says. Even if it doesn’t, consider taking an educated guess and apply strips within the field to see what takes care of the problem, he says.

“With nutrient balance levels declining nationwide, it’s important for farmers to be vigilant and identify deficiencies in their crops before it’s too late,” Mullen says. “After conducting this process, there is a chance not every problem will be solved, but these five steps will help get your yields back on the right track.”

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