No-till production systems are especially hard on applied fertilizer and are a perfect environment for post-application losses of phosphorus (P) to naturally occurring chemical reactions in the soil. Whether the fertilizer is applied in the spring or fall, or in liquid or dry form, chances are a no-till system will translate into increased losses of P due to that element becoming “fixed” in the soil.
“The two pathways to the breakdown and the potential loss of nutrients are moisture and temperature, which work in tandem to either lock in nutrients or lose them,” says Dr. Ron Heiniger, Professor of Cropping Systems at North Carolina State University. “As a rule, cool and dry is good, and warm and wet is not when it comes to soil conditions.”
A warm and wet environment speeds up microbial activity, and water moving through a permeable soil profile acts as a transport mechanism and also contributes to nutrient losses, Heiniger notes.
Higher Risk of P Losses
“In a no-till environment, you have a greater buildup of carbon and organic matter, and therefore a soil that is much more active and nutrient transformation is more enhanced,” Heiniger explains. “Your nutrients are much more at risk in no-till systems.”
The hard fact for P fertilizer is that between 75 and 95 percent of the nutrient often gets tied up or “fixed” in the soil. Within days or weeks after application, P undergoes a fierce reaction that converts it from a soluble to an insoluble form and makes it unavailable for plant uptake.
“The fixation of P in the soil is a huge deal – you can’t know when P might revert to a form that is available to the plant,” Heiniger says. “For this reason, a farmer who applies 200 pounds of P in the fall might only realize benefits from 10 to 50 pounds of the nutrient the following spring.”
Technology Reduces Soil Fixation
Heiniger notes that, fortunately, there is technology available to the farmer that reduces fixation of P in the soil and helps to ensure the nutrient remains in the soluble form and can be readily used by crops via plant uptake the following spring. The technology is AVAIL® Phosphorus Fertilizer Enhancer, and it can either be impregnated on to granular fertilizer or injected into liquid fertilizer.
“AVAIL is a nutrient enhancer that targets P,” Heiniger explains. “The product provides a negative charge that protects P from getting tied up with positively charged cations in the soil.”
The end result of this technology, he adds, is that crop root systems are larger, crop emergence is more vigorous and plants are healthier overall due to the improved uptake of P.
Uptake of P Critical
“Having ample P for crop uptake is especially crucial under a no-till system,” says Dr. Barney Gordon, Professor Emeritus of Agronomy at Kansas State University. “The surface residue, whether it is corn stalks or wheat stubble, for instance, cools the soil and prevents it from rapidly warming up,” he explains. “Plant roots grow slowly and are challenged to cover the soil volume necessary to absorb the nutrients and moisture they need for growth. In this situation, it is essential to have P in the root zone and available for crop uptake.”
Gordon also recommends use of AVAIL as a means of reducing soil fixation of P, helping to ensure increased amounts of the nutrient will be available for plant uptake under a wide range of soil conditions.