Joel Ransom, NDSU Department of Plant Sciences
Jasper Teboh, NDSU Carrington Research and Extension Center

Nitrogen is the most important applied fertilizer and is usually the most expensive input in corn production. Management practices that maximize the return to the nitrogen applied is critical for the profitability of a farming operation and for the environment. There are a number of fertilizer products available that slow the rate of N release from the fertilizer granule (ESN) or slow the conversion of ammonium-N to nitrate-N. ESN, SuperU™, and Instinct II™ were the products used in this research. Keeping N in the ammonium form longer can reduce the potential loss of N from the soil leaching or volatilization.

An alternative N source is distillers grain (DG), an important by-product of ethanol production. This by-product is valued as a source of animal feed that stores and transports well when dried. However, when there is excess DG production relative to demand, there may be periods when the ethanol plants may need to sell it locally for use as a fertilizer, especially if it can be used prior to drying. Local research is needed to evaluate the performance of wet DGs (WDGs) as a nitrogen source.

The objectives of this research were to determine the fertilizer equivalent value of WDGs for corn production and to determine the best management practices for new fertilizer products that delay the conversion of nitrogenous fertilizers to nitrate.

Field experiments were established in three locations in 2015 and 2016 . Treatments consisted of nitrogen rates at 75%, 100% and 125% of the optimum rate, and nitrogen source (urea, urea at planting + UAN at V6, WDGs, 50:50 WDGs + urea, ESN™, and SuperU™ , urea + Instinct II, and an unfertilized check). Treatments were established in small plots and replicated four times at each location. All fertilizers were broadcasted and incorporated prior to planting, except surface applications of UAN and all treatments at the 2016 Carrington no-till site.

A chemical analysis of the WDGs revealed that they are a rich source of N, P, K, and other nutrients, containing about 4% nitrogen on a dry wet basis. Data from the Casselton location were not included due to excessive variability or non-responsiveness to treatments. Averaged over nitrogen sources, yield increased as the rate of N applied increased. At the lowest application rate, applying WDGs resulted in lower yield and protein when compared to other treatments of the same rate. This suggests that some N in the WDGs was not mineralized quickly enough to meet the demands of the corn. Limited data suggest that fall applications of WDGs may hasten the mineralization of N compared to spring applications of WDGs.

We concluded that WDGs are an alternative source of N, P, K, and other plant nutrients, and can be used as a substitute for N fertilizers. However, if using WDGs exclusively, they should be applied at least at 125% the optimum N rate when compared to other N sources to elicit an equivalent response.

In the environments of this study, alternative fertilizer sources and additives showed no apparent benefit over urea, and therefore were not cost-effective. However, it would be useful to compare these fertilizer sources and additives in environments conducive to N losses in the future. Environments with significant N loss may evoke a positive response from slow release and nitrification inhibiting products if they are indeed effective in keeping the nitrogen in the ammonium form longer to reduce N loss.