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New Technology To Improve Phosphorus And Potassium Efficiency
KYLE LILLY And DR. JOHN D. BAILEY
SPRINGERTON, ILL.
Applying phosphorus (P) and potassium (K) fertilizer in the fall is a common practice in the United States. During the fall, soils tend to be drier, fertilizers are readily available, workloads can be spread out over the year, and P and K can be incorporated with fall tillage. Additionally, fall-applied P and K can become more available to a spring crop by having more time to break down. Fall application of P and K can also help farmers reduce environmental risks due to lower runoff risks during typical fall weather and soil conditions.
While fall application of P and K has many practical benefits, farmers often ask why they do not often get higher yields with higher application rates of granular P and K. Iowa State University studies conducted by Mallarino (1995) reported statistically significant yield responses to increased broadcast P in only 1/3 of 240 documented trials. With respect to broadcast K, a 2013 analysis of 2,100 studies from the University of Illinois found that broadcast K gave a significant yield increase only 24 percent of the time (Khan et al., 2013). Farmers are asking some critical questions when it comes to fall-applied P and K fertilizers. Why do less than 50 percent of P and K fertilizers get taken up by the crop? Where does the fertilizer go? How can farmers improve the efficiency of P and K fertilizer?
Phosphorus Losses
Phosphorus is generally considered immobile in the soil but major losses can occur. It does not leach through the soil like nitrate nitrogen, however, after MAP or DAP dissolves, P can tie up with different compounds. These loss pathways are mostly related to organic matter and pH.
Phosphorus tie up by organic matter happens when available P attaches to residues, manure, and other soil organic particles. The P eventually frees up through a process called mineralization. Enzymes produced by plant roots, soil bacteria, and fungi convert organic P into plant-available inorganic P. P tie-up by organic matter is one of the reasons growers often see high soil P levels but find that the P is not getting into their crop. It is there but just not available.
Another type of loss occurs when P attaches to calcium in higher pH soils or to aluminum and iron in lower pH soils. The optimal pH for P availability is between 6.5 and 6.8. Farmers may help reduce P tie-up by balancing soil pH and using products containing humates or other molecules that directly compete with Ca, Al, and Fe in binding to soluble P.
Permanent P loss can occur if soils undergo erosion. Water flowing across the soil surface can dissolve and transport soil and soluble P or simply carry fertilizer away. These losses are not only bad for the farmer’s pocketbook, they can also cause significant environmental damage to lakes, rivers, and oceans. Many erosion control practices have been developed and are being applied, such as conservation tillage, contour plowing, terracing, buffer strips, and grassed waterways.
Potassium Losses
Potassium (primarily from potash fertilizers) is also considered relatively stable in the soil. The major concern with K loss is its tendency to fix into the soil matrix, similar to how P ties up with calcium, iron, or aluminum. The release of fixed K depends on soil moisture, aeration, oxygen level, and temperature. The soil is able to move this K back and forth between particles and through a soil solution much more rapidly than with P.
Two other potential K losses are from leaching and erosion. Unlike P, K is more mobile in the soil, but this depends on soil texture and the type of clay particles present. K can move readily in sandy soil with low CEC, whereas, leaching losses of K are rare in heavier soils with high CEC. K losses can be minimized by using best management practices like incorporating fertilizer and avoiding fall applications on sandy soils with low CEC.
New Fertilizer Additive Improves Fall P and K Fertilizer Efficiency
While nitrogen (N) fertilizer additives have become relatively commonplace in the market to address volatility, denitrification, and leaching losses of N, existing additives for P have not proven successful (see Chien et al., 2014). Duo Maxx, manufactured by Timac Agro USA, is the newest innovation in the additive market, designed to address P and K efficiency. The product works by reducing fertilizer loss, improving the availability of nutrients, and stimulating root uptake.
Duo Maxx contains an organic binding agent called MPPA, which binds to both positively and negatively charged fertilizer and soil nutrients. While bound, these nutrients are protected from tie-up to organic matter and other nutrients like calcium, aluminum, and iron. The MPPA molecule is also quite large and protects against leaching. MPPA bonds are sensitive to root exudates, which break as plant root growth increases. Nutrients are then released and available as plants need them.
Duo Maxx can also help protect the N in common P fertilizers. MAP and DAP contain N in the ammonium form, which is positively charged and can directly bind to the MPPA molecule. This helps protect the N in MAP and DAP from denitrification and leaching.
The final component of Duo Maxx is a patented root biostimulant that enhances communication between soil microbes and roots, resulting in substantial increases in root mass and root hair development. Increased root growth can drastically increase fertilizer efficiency by enhancing fertilizer uptake. Since Duo Maxx has been shown through third-party testing to improve not only P and K uptake but also N, it represents the most advanced innovation in fertilizer additives on the market today (San-Francisco et al., 2005; Garcia-Mina et al., 1997; Garcia-Mina et al., 1994).
While there are no magic bullets for solving the issue of P and K losses, the use of best management practices and new fertilizer additive technology, like Duo Maxx, can help enhance fertilizer efficiency, improve environmental stewardship, and protect a farmer’s bottom line. ∆
Kyle Lilly, CCA, CPSS and Dr. John D. Bailey: Production managers with Timac Agro
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