Soil study affirms P, K levels can impact yields


DES MOINES, Iowa — Critical analysis of yield results from the 2016 growing season further affirmed a DuPont Pioneer study released in August 2016 that indicated growers may be leaving profit potential in the field by not carefully managing phosphorus (P) and potassium (K) levels.

“Growers have told Pioneer that they think improving soil fertility management is one of the best ways to increase corn and soybean yields,” said Rick Radliff, DuPont Pioneer senior agronomy manager. “In Iowa alone, our results indicate that marginal soil fertility may contribute to hundreds of millions of dollars in lost revenue each year.”

State recommendations

With data from Iowa and across the Corn Belt, Pioneer found that yields trend lower in areas where phosphorous and potassium levels fall below state recommendations.

This aligns with previous research conducted at Iowa State University, indicating a 65 percent to 80 percent probability of positive yield response by fertilizing to raise P or K soil-test values from very low or low to optimum (Iowa State University Extension PM 1688).

The data also showed that the highest corn yields did not benefit from P and K levels that were above the optimum recommended amount; however, more work needs to be conducted as some growers are striving for much higher yields.

Additionally, data variability indicates other factors could influence crop yield, such as soil compaction, planting date and population, drainage, foliar disease, insect feeding and weather.

Soil testing

DuPont Pioneer agronomists advise that these challenges can be addressed through regular soil testing, a clear understanding of each field’s yield potential and a field-by-field fertilizer program that results in the biggest return on investment.

“Managing soil fertility is complex,” said Radliff. “Through offerings such as EncircaSM Fertility services, growers can access resources to help them achieve their goals.”

The study was conducted as part of the Pioneer GrowingPoint agronomy program, which provides valuable crop-management insights for growers on production practices to help growers improve productivity and profit potential.

Pioneer sampled nearly 9,000 fields between 2015 and 2016, with some fields in 10 Corn Belt states showing at least some deficiencies in soil phosphorus levels. This can lead to issues with early root and shoot growth and can reduce tolerance to drought, disease and temperature stresses.

The same samples found that four Corn Belt states had at least some deficiency in potassium in its soils, which affects water regulation, enzyme activation and promotes stalk strength and late-season standability.

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