An Overview and Decision Guide for Using Enhanced Efficiency Fertilizers in Corn Production as a Nutrient Management Tool in the U.S. Midwest

Abstract

Nitrogen stabilizers can be a valuable and effective management tool to manage nitrogen losses and increase plant available nitrogen for corn production in Midwestern United States. Dynamics of the nitrogen cycle (Appendix A) in crop production generates nitrogen losses from nitrate (NO3-) leaching through the soil and denitrification into the atmosphere as gaseous forms of nitrogen such as nitrous oxide (N2O) and dinitrogen. Soil ammonium (NH4+) can also lose through volatilization as ammonia gas (NH3) into the atmosphere. Nitrogen losses depend on fertilizer management practices such as N application timing, source, placement, and N rate, as well as management and environmental conditions such as tillage, soil types, and weather patterns. Therefore, important and complex management decisions, which can be difficult to make, must be addressed every year vis-à-vis N fertilizer cost and management to maximize the returns on the inputs of commercial corn production. In many situations, the potential for N loss in corn production may be high, and the use of N fertilizer stabilizers may decrease N losses and increase N use efficiency. There are currently three major categories of enhanced efficiency fertilizer products on the market including nitrification inhibitors, urease inhibitors, and polymer-coated urea. These products can be applied to the three most common N fertilizers: anhydrous ammonia, UAN, and urea (Ferguson et al., 2019). There are two reasons we need to work on Enhanced Efficiency Fertilizers, or EFF’s, or “stabilizer products”: 1.) There are many different chemistries – not all products are the same even within one of the three modes of action mentioned previously (nitrification inhibitor, urease inhibitor, and polymer); and 2.) Whether these products work is an outcome of not just the chemistry, but how it interacts with complex GxExM complexities of the system (genetics, weather, soil type, management, etc.). An increasingly large number of products on the market within these broad categories makes it difficult for corn growers to select the best product. Not all products are chemically the same. Products may contain ingredients with known efficacy such as N-(n-butyl) thiophosphoric traimide (NBPT), and N-(n-propyl) thiophosphoric tramide (NPPT), which inhibit urease activity. There are ingredients such as dicyandiamide (DCD), nitrapyrin, and pronitradine that have shown efficacy in nitrification inhibition (Iqbal and Thompson, 2021). The chemistry of these ingredients is no longer patent-protected (Iqbal and Thompson, 2021), and many other products list those active ingredients on labels at lower concentrations, or different formulations in which research has been conducted on their effectiveness as nitrogen stabilizers. Many corn growers may also not understand that adding N stabilizers may not result in yield or profit increase. Thus, it is essential that corn growers understand weather situations, and soil conditions that are conductive or non-conductive to N losses. If weather and soil conditions are not conductive to N loss, there is no benefit purchasing and using these types of N inhibitors. It is also important to understand N levels in the soil, and rates to establish how much N loss will impact crop yields and by what margin from the yield potential. Typically, excessive N rates will not show any benefit from N stabilizers. Therefore, it is important that corn growers understand the N inhibitor products, labels, modes of action, and how to effectively adopt those products to manage N loss on their corn farms.