Nutrient use efficiency (NUE) is simply the pounds of nutrient applied divided by the yield of the crop. It can be calculated for any nutrient. As a ratio, NUE can help farmers better understand fertilizer consumption on their farm and maximize crop performance while optimizing up-front nutrient inputs. Lower NUE values signify more efficient nutrients. Weather, soil type, soil texture, organic matter, crop, soil biology, pests, nutrient interactions, management practices, and many other factors affect NUE. In this article, we discuss how to use nutrient interactions to get the most out of soil-applied phosphorus and potassium fertilizer.
First, it is important to understand that nutrients have interdependent relationships that influence their availability and efficiency. This was first described in the 1940’s by E. B. Mulder. Over the years, it has been simplified to a single chart now known as Mulder’s Globe. For example, it shows that nitrogen availability is related to boron, sulfur, and potassium; phosphorus availability is related to sulfur and zinc; potassium and magnesium influence each other. Too much of one nutrient can cause a deficiency of another nutrient or too little of one nutrient prevents the uptake of another. The take-home point is that the most efficient nutrients come from a blended fertilizer that attempts to balance these relationships.
Furthermore, this approach must take into account existing soil fertility and the knowledge that all nutrients are affected by soil pH. Therefore, after addressing soil pH, the first step in creating efficient phosphate and potassium fertilizer is to introduce sulfur in the form of AMS to the blend. Sulfur improves the uptake of both of these nutrients. The AMS form of this nutrient creates localized small changes in pH that improve the availability of nutrients like manganese and iron which further improves P and K uptake. Additional fertilizer improvements come from introducing important micronutrients into the blend. Liquid or liquid-impregnation most efficiently spreads the small amounts of these nutrients across an acre. Boron, Manganese, and Zinc are among the most important micronutrients to add to P and K fertilizer blends.
Next, organic matter or more specifically humics, the active portion of organic matter, is able to slow the loss of nutrients and facilitate uptake. This stretches nutrients further and encourages the growth of plants and microorganisms which improves soil and plant health. Hydra-Hume® is a high quality humic acid that can be blended into the fertilizer to gain these benefits. Hydra-Hume is blended per ton of fertilizer.
Thus, Hydra-Hume “treats the ton, not the acre”. ASK® blends are improved P and K fertilizers created by blending them with AMS, Hydra-Hume, and liquid/impregnated micronutrients to create a balanced nutrient load. Taken together, using ASK blends, a farmer can apply fewer pounds of nutrient (K2O or P2O5) while retaining or improving yield. This is the definition of efficiency. Helena has been recommending ASK blends for years and documenting their efficacy over a broad number of acres and environments. Across all years and environments ASK blends deliver an average of 6 bu/A increase in corn yield. For example, at our research farm Huntington, IN, in 2019 we conducted a corn trial to compare 2 rates of ASK blends verses MAP and Potash alone or a blend of MAP/Potash with elemental sulfur and dry micronutrients (Table 1 below). The fertilizer blends were applied in the fall. Figure 2 above is the result of that trial. Yield is the average of 4 replicates of each blend. ASK delivered a 3-4% increase in yield (bars) and improved P and K NUE by 37% (lines). Note the ASK Low treatment is 50 lb/A less fertilizer that resulted in 8 bu/A increase in yield.
— Ben Wilson, Ryan Lee, Randy Simonson North Central Division Agronomists