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Enhanced efficiency P technologies show potential

Research and development continues on enhanced efficiency phosphorus (P) fertilizer products, including controlled-release, polymer-coated and shielded products. Although research in parts of the US has shown benefits from some products, the research in Western Canada and the Northern Great Plains shows little yield benefit.


February 24, 2010
By Donna Fleury

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Research and development continues on enhanced efficiency phosphorus (P) fertilizer products, including controlled-release, polymer-coated and shielded products. Although research in parts of the US has shown benefits from some products, the research in Western Canada and the Northern Great Plains shows little yield benefit.

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Avail research trials in Alberta.   
Photos courtesy of Rigas Karamanos


 

Researchers are still trying to fully understand the chemistry, soils, fertility levels and other factors to find answers. “Enhanced efficiency P technologies are still of great interest to researchers, industry and farmers, but from a research perspective we need to show a value for using these products,” says Ray Dowbenko, senior specialist in agronomy with Agrium Inc. “In theory these products make a lot of sense, but unlike controlled-release nitrogen (N) we haven’t been able to show yield benefits with P products so far. The enhanced efficiency P products do have value in terms of getting more P into the plant, making it more efficient and addressing issues such as seed safety and crop maturity.”

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Recent research conducted by Dr. Cynthia Grant at the Agriculture and Agri-Food Canada (AAFC) Research Centre in Brandon, Manitoba, and Dr. Jeff Schoenau at the University of Saskatchewan in collaboration with Agrium, does show benefits to seed safety, and enhanced uptake and availability of P. “The research does show enhanced uptake of P and better performance with coated products, but at the end of the day the yields aren’t that much different,” explains Dowbenko. “Some of the AAFC research showed a 2 bu/ac yield benefit and three or four days shorter time to maturity, but growers have to determine if they feel that’s enough value to offset the cost of these inputs.”

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Research trials comparing 45 lbs of P2O5 per acre, with and without Avail


 

Schoenau’s research compared seed placement of various rates and types of P at up to 80 pounds and still found seed safety with coated P products. “For growers seeding peas, canola or lentils that require higher rates of P, the safety showed by the coated products in the seed row could be beneficial,” says Dowbenko. “The P could be applied in one pass, saving fuel and time during seeding.” Agrium’s controlled-release P technology is still in the research and development phase, and commercialization continues to be of interest to the company. However, further field research and manufacturing considerations are needed.

Other products, such as Avail may be added to P fertilizer before application with the objective to protect or shield the P from being tied up by calcium, magnesium and other chemicals in the soil, to keep P more available for plants. Research to date in Western Canada and the Northern Great Plains shows little yield benefit. Researchers are not sure if it is the soil chemistry, the high average levels of calcium and other chemicals in Prairie soils or other factors.

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“We have a total of six site years of research with Avail at Kindersley, Brandon and at the Ellerslie and Breton research sites in Alberta,” explains Dr. Rigas Karamanos, agronomy manager with Viterra. The research compared three rates of P2O5: 15, 30 and 45 lbs per acre, with and without Avail and a control. Overall, none of the plots showed a yield or straw benefit to using Avail. The data from the 2009 trials is not yet available, but results are not expected to be significantly different from the previous two years.

“At this point, there doesn’t seem to be a benefit of using enhanced efficiency P products in the main growing areas of Western Canada,” says Karamanos. “There may be conditions such as very sandy soils under irrigation or soils with low organic matter where they may be a benefit. In areas such as the volcanic soils in Idaho, there is a real benefit to using these products, but not for most of our Prairie soils.”


More research needed

Researchers agree that to truly answer the questions about what products work, and where and when they will provide the most benefit, there needs to be more long-term research. The limited research information thus far makes it difficult to provide good answers or recommendations to farmers.

Dr. Clain Jones, extension specialist at Montana State University, conducted a review of enhanced efficiency N and P fertilizer technologies, with input from researchers including some from Western Canada in July 2009. (msuextension.org/publications/agandnaturalresources/EB0188.pdf) Research is limited for enhanced efficiency P products, and what is available so far shows limited benefits. Jones notes that the greatest benefits of using enhanced efficiency P products will be expected where nutrient losses and/or limited nutrient availability limit crop yield, or where seedling damage from applied fertilizer is sufficient to reduce crop yield. He also notes that these products generally delay the release of nutrients: therefore the timing of application is important. 

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Enhanced efficiency P technology may improve yield and maturity, but a better understanding of economics is needed. (Photo by Bruce Barker.)


 

“Based on earlier internal Agrium research, we found that controlled-release P products do increase P uptake. We found similar yields with reduced rates of controlled-release P fertilizer, which would allow growers to apply these products at a lower rate, possibly one-third to one-half less than the rates of normal fertilizer, which would save them money,” says Dowbenko. “However, we need to conduct long-term research to determine if over time the reduced rates of controlled-release products may actually reduce the P bank in the soil that resupplies P during the growing season.”

“The enhanced efficiency P fertilizers do show interesting potential, but we need more research to answer a lot of questions for farmers,” adds Dr. Ross McKenzie, research scientist in agronomy with Alberta Agriculture and Rural Development (AARD) in Lethbridge. “These products may have some opportunity, but it would take a significant amount of research across the Prairies on different soil types and different crops to determine when they might work and when they won’t.”

McKenzie notes they did submit a research application supported by Agrium in 2008, but it was turned down. That long-term, five-year research project would have answered a lot of questions about the potential benefits of enhanced efficiency P technologies, whether or not farmers could use lower rates with enhanced products and the long-term impact of their use on P soil levels and the environment. McKenzie, Agrium and other industry partners are still interested in this research to see if there is an advantage to these products under Prairie conditions.


Soil chemistry and P fertilizers

Phosphate fertilizers need to be placed close to plant roots to be
available, and because they are soluble can quickly shift into less
available forms. “When ammonium phosphate fertilizer is banded or
seed-placed in moist soil, the granules rapidly dissolve and phosphate
enters the soil solution for plant uptake,” explains Dr. Ross McKenzie.
“Unfortunately, negatively charged P is highly reactive with cations in
soil, including calcium and magnesium in higher pH soils, and aluminum
and iron in lower pH soils, resulting in the plant-available P bonding
with these cations and causing a shift to less available P forms, which
reduces plant uptake.”

Plants need to access P starting about seven to 10 days after
germination and take up about 70 percent of their P fertilizer
requirements in the first 35 to 40 days after emergence. “We know the
absolute best efficiency of seed-placed P fertilizer in the year of
application in Western Canada is 30 to 35 percent; sidebanding, about
20 to 30 percent; and broadcast and incorporated, 10 percent,” says
McKenzie. “This means that about 70 percent of applied P fertilizer is
not taken up in the year of application, but is available for uptake by
future crops. The question is can we increase this efficiency by using
enhanced-efficiency P fertilizers and would that allow farmers to cut
back on P fertilizer rates?”