Jasper Teboh, NDSU Carrington Research Extension Center

Farmers in North Dakota have been asking if the co-products, condensed distillers solubles (CDS) and wet distillers grains (WDGs) from corn ethanol production can be used as viable sources of fertilizer. In 2015, CDS and WDG were obtained from the same ethanol plant and analyzed for their nutrient content. Based on the analysis, they were applied as P fertilizers to assess their effects on corn yield in Carrington (CREC) and Fairmount, ND. Triple super phosphate (TSP), CDS, and WDG were surface applied and incorporated in the soil at 40, 80, and 120 lbs P2O5/acre rate, including a check (0 lbs added P). The CDS and WDG treatments received no additional fertilizer. The check and TSP treatments received N as urea, up to the total amount of N applied at the 80 lbs P2O5 rate as CDS. Grain yields, protein, test weights, and nutrient analysis were recorded. We also conducted a laboratory incubation test of available P over time of application of all three sources of P.

Results from Fairmount showed yield response to P rates and sources was not statistically significant. However, yields were higher when P was added. Grain yields increased by P source in the order: Check<TSP<CDS<WDG (i.e., 182, 187, 189, and 192 bu/ac, respectively). In Carrington, yield responded significantly to P rates (p<0.0196) and P sources (p<0.0008). Mean yields were, 128 bu (check), 132 bu (40 lbs P2O5), 138 bu (80 lbs P2O5), and 143 bu (120 lbs P2O5). The mean yield at 120 lbs P2O5 was significantly higher than the check but not the rest of the P treatments. Yields from all P treated plots were not statistically different from each other. On sources of P, the only significant yield difference due to P sources was between the CDS (147 bu) and check (128 bu) treatments. Yields increased by P source in the order Check<TSP<WDG<CDS (i.e., 128, 130, 136, and 147 bu/ac, respectively). On average, CDS produced 11 bu more than WDGs, and 17 bu more than TSP.  There were no significant responses of grain protein, test weight, height, to treatments even though CDS consistently produced the lowest grain protein, and the tallest plants. Grain nutrient analysis from Carrington samples showed higher P uptake with P rates. Preliminary results from Incubation study showed that P availability from CDS was quite high following analysis within one week of application. The amount of P measured from the CDS soil treatment gradually declined over time.

From the first year results, there is strong evidence that distillers grains can be good sources of phosphorus and other nutrients for corn. The economics of using either CDS or WDG were not evaluated in this first year of study; however, their use as fertilizer sources must be balanced against their costs of acquisition, and application logistics.

The authors gratefully acknowledge the North Dakota Corn Council and Greg LaPlante for providing support for this work. Special thanks to Tharaldson Ethanol, Hankinson Renewable Energy, LLC, and Green Plains, Inc. for providing the distillers grains co-products for this study. We also thank Mr. Chad Deplazes, Mr. Grant Mehring, and Mr. Ezra Aberle for their tremendous field support.