It is generally accepted by growers and researchers that nutrient losses can be more pronounced in no-till production systems due to increased soil microbial activity, soil temperature and other factors. Plant uptake of nutrients can be especially challenged due to increased post-application losses of phosphorus (P) and nitrogen (N) fertilizers.
These losses can be offset and reduced, however, by making P applications in the fall and using fertilizer enhancers or stabilizers with both fall-applied P and spring-applied N.
“You have a greater buildup of carbon and organic matter, microbial activity speeds up and nutrient transformation is more enhanced in no-till systems,” says Dr. Ron Heiniger, professor of cropping systems at North Carolina State University. “Plus, water moving through a more permeable soil also contributes to nutrient losses.”
In the case of P, between 75% and 95% of the nutrient often gets tied up or “fixed” in the soil the year of application due to a chemical process that converts it from a soluble to an insoluble form and makes it unavailable for plant uptake. Nitrogen losses can also increase from leaching, volatilization and denitrification due to higher amounts of soil organic matter and mineral components found in no-till systems. “This increased microbial activity works in tandem with moisture and temperature to either lock in or lose those nutrients,” Heiniger says.
Phosphorus Fixation Delays Availability
“The fixation of phosphorus in the soil is a huge deal — you can’t know when phosphorus might revert back to a form that is available to the plant,” he continues. “Fortunately, there is technology available that reduces phosphorus fixation and helps ensure that the nutrient remains in the soluble form and can be readily used by crops.”
That technology exists, with an example being AVAIL Phosphorus Fertilizer Enhancer from SFP. This can be used to either be impregnated on granular fertilizer or injected into liquid fertilizer.
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“AVAIL is a nutrient enhancer that targets phosphorus by providing a negative charge that protects phosphorus from getting tied up with positively-charged cations in the soil,” Heiniger says. “The end result is larger root systems, more vigorous emergence and plants that are healthier overall due to the improved uptake of phosphorus.”
Reducing Nitrogen Losses
No-till conditions also provide many mechanisms for loss of N due to increased residue cover and increased exposure to the climate, notes Dr. Barney Gordon, professor emeritus of agronomy at Kansas State University (KSU). “Plant roots grow more slowly and are hard pressed to cover the soil volume needed to take up ample moisture and nutrients,” Gordon explains. “Combine this scenario with higher nitrogen losses, and the crop is going to struggle.”
A helpful way to counter N losses in no-till is to use products such as NutriSphere-N Nitrogen Fertilizer Manager. “NutriSphere-N keeps more nitrogen in the ammonium form versus the nitrate form,” Gordon says. “Plants can take up nitrogen in the ammonium form and utilize it with less energy conversion, so more energy goes into plant development, growth and yield. Otherwise, the plant has to use energy to convert nitrate to ammonium so the nitrogen can be more directly utilized by the plant.”
Gordon notes that, in general, conditions favoring loss of applied N fertilizer include:
- High soil temperatures.
- Moist conditions, followed by rapid drying.
- High amounts of surface residue.
- Windy conditions.
- High soil pH (greater than 7.5).
- Coarse soil texture, such as sandy soils.
- High lime content on the soil surface.
- Amount of water moving through the soil profile from rainfall or irrigation.
Fall P Application Recommended
The KSU researcher also notes that P has a tendency to hang out with the wrong crowd. “In high acid soils, phosphorus gets tied up with iron and aluminum,” the agronomist says. “In high-pH or low acid soils, phosphorus tends to bind to calcium and magnesium. Soil tests may only tell you the amount of phosphorus in the soil — not what is actually available for plant uptake by the crop. In many cases, phosphorus needs help to increase its availability to the crop.”
Applying P in the fall and using an enhancer such as AVAIL is one of the best hedges against P tie up in the soil, as well as weather delays in the spring, according to Gordon. “Spring tends to be a wetter period of the year, and a farmer can nearly always count on missing a number of days in the field to wet weather,” he says. “If you wait until spring to apply phosphorus, you run the risk of not getting it applied in time to benefit your crop.”
There is also a larger window for P application in the fall, due to larger equipment and quicker harvests. The agronomist recommends the use of AVAIL to help ensure that adequate P will be available for plant uptake the following spring. “There is plenty of solid research data that demonstrates fall phosphorus applications are just as effective as spring applications,” Gordon says. “Corn really needs phosphorus to get a good start, and if applications are late you can experience some deficiencies.”
Gordon cites KSU research conducted from 2008 through 2010 which showed a 12-bushel per acre corn yield advantage when AVAIL was applied with monoammonium phosphate (MAP) fertilizer.
“Depending on commodity prices, it only takes two or three bushels of extra corn yield to pay for the AVAIL treatment,” the researcher says. “The rest of the yield increase is money in the farmer’s pocket.”
Narrowing Your Spring Focus
From a farm dealer and custom applicator perspective, fall is the right time to apply P. “You really get ahead of the game if you apply your phosphorus in the fall,” says Matt Bambauer of Bambauer Fertilizer and Seed in Pemberton, OH. “There’s just way too much for a farmer to manage in the spring without having to worry about fertilizer applications.”
Spreading that crop-production workload out over the fall and spring can be a life saver for the farmer, especially when the spring is wet and cool and throws all planting-related activity behind schedule. It can also be a life saver for professional applicators, whose ability to meet customer needs can be stretched thin by spring weather delays.
“In the spring, the farmer should be focused on nitrogen applications, planting and controlling weeds, insects and diseases,” Bambauer stresses. “Those items alone demand a farmer’s full attention, because getting the crop off to the best possible start is key to success for the entire growing season.”
There are also sound agronomic reasons for applying phosphorus in the fall, Bambauer says. “It takes time for phosphorus to break down after application and move through the soil profile, especially in a no-till production system,” he explains. “You also need time for phosphorus to be adequately incorporated either by rainfall in a no-till system or by tillage in a conventional system, and fall weather is usually optimal for both.”