There is growing interest from farmers to know if distillers grains (DGs) could be used as a cheap alternative or supplemental input for cereal production. Condensed distillers solubles (CDS) and wet distillers grains (WDG) are co-products from ethanol production that are mainly used as sources of feed for livestock. They are sometimes available to farmers when in excess of demands as feed, or when for whatever reason, the plant encounters some storage limitations, and have to dispose of the products. Potential environmental problems and cost of freighting huge loads to distant places for disposal has been a concern for ethanol plants. However, the cost of procurement and transportation of DGs, storage, and availability of appropriate equipment to apply these products to farmlands, are some of the bottlenecks for farmers interested in their value as fertilizer sources. Despite these concerns, farmers who farm in close proximity to ethanol plants, or who have the means to transport and apply these products in nearby fields are the ones likely to benefit from the DGs as fertilizer inputs. Preliminary studies indicate that when DGs are applied to soil as sources of nitrogen (N) or phosphorus (P), yields have been similar or better in comparison to synthetic fertilizers. Farmers also appreciate the environmental value in that nutrients removed with the corn following harvest from their fields to the ethanol plants can be recycled back to farmlands. Procurement of DGs by farmers also creates and enhances a synergism between farmers and the ethanol plants, considering the latter could cut down on storage, drying, or disposal costs if farmers are willing to buy or take any excess DGs.
What Did We Do?
Methods are reported for field studies that assess the effects of P from three sources on grain yield and quality of corn in 2017, and wheat in 2017 and 2018. Study sites were located at the NDSU Carrington Research Extension Center, Carrington (ND). The P sources were CDS, WDG, and triple super phosphate (TSP) fertilizer. Rates of P were 0, 40, and 80 lbs P2O5 for wheat in addition to 120 lbs/ac for corn. Wheat treatments in 2017 and 2018 included surface application versus incorporation following application. The weight or volume of WDG or CDS applied varied by year, depending on the nutrient analysis. In 2018, to apply 20 lbs P, 3.3 T/ac of WDG, and 270 gallons/ac of CDS were required. At these rates, 112 lbs N, 17 lbs S, and 27 lbs K2O were applied with WDG. CDS contributed 32 lbs N, 31 lbs K20, and 15 lbs S at the 40 lbs P rate. Urea was applied up to the N rate recommended (79 lbs) to prevent deficiency for the check (0 lbs P) and TSP treatments, and less for the 40 lbs P rate of CDS. Sulfur (as ammonium sulfate) was also added to the check plots and those that received TSP. Treatments were surface applied and incorporated. CDS was mixed with water to facilitate manual application to the small plots, 5 x 25 ft.
What Have We Learned?
In 2017, P did not impact yields for both corn and wheat trials. This was probably due to high soil P level, 16 and 13 ppm P from the corn and wheat respective fields, before planting. P sources did not affect yields. Following harvest, P removed with the grain, on a dry weight basis, was significantly greater with WDG (76.2 lbs/ac) compared to TSP (69 lbs). The difference in grain P removed between WDG and CDS (75.7 lbs/ac) was not statistically significant. Neither yields nor protein differed between P sources.
In 2018, yields improved significantly from P application with DGs and TSP as sources. The P unfertilized plot (0 lbs P) produced 42 bushels, which was significantly less (by 10 bushels) than yields at 40 lbs P. Yields were also significantly less at 40 lbs P (by 5 bushels) compared to 80 lbs P. Yields produced by CDS, WDG, and TSP were similar (54 bushels). Earlier in the season, Normalized Difference Vegetation Index data were collected using a remote sensor to provide an index of crop vigor. There were no differences in vigor between P rates. Meanwhile, the crop vigor of TSP treatment was significantly greater than for both DGs. This was likely due to better availability of P and N, early in the growing season, from urea and TSP. However, these nutrients were later available after mineralization from DGs, in amounts that were adequate to satisfy the crop’s needs similar to respective P rates from TSP. Grain P removal was not different between P sources. When averaged across P rates, P removal in the grain was 33 lbs P2O5. Grain P removal was 23, 30, and 35 lbs/ac at 0, 40, and 80 lbs rates, respectively.
Grain protein was significantly greater with WDG compared to CDS and TSP, probably due to higher N applied with DGs at the 80 lbs rate of P, 223 lbs N at 80 lbs P compared to 79 lbs applied with TSP and CDS on a soil that already had 47 lbs and previous crop was soybeans.
Considering the 2018 results and results previously reported from the 2015 and 2016 trials, CDS and WDG can be valuable sources of P and other nutrients for grain crops in North Dakota. For farmers who can transport DGs short distances, pay little or nothing for it, and apply with their manure applicators, they should feel comfortable applying DGs as a good source of P and N.
Some farmers have been curious about the dried distillers grains as P sources. We will conduct another study in 2019 including the dry product (DDG), even though we understand it is very unlikely that farmers would make any profit with the dry product as a source of nutrients.
Jasper M Teboh, Research Soil Scientist, NDSU – Carrington Research Extension Center
Szilvia Yuja, Research Soil Specialist, NDSU – Carrington Research Extension Center
Where can people go to learn more about this project or research? List journal articles, websites, publications, articles, social media, or other resources.
Please contact me with questions at Jasper.Teboh@ndsu.edu, or by phone at 701-652-2951 (Ext 109).
Results from this research were first presented at the ASA/SSSA/CSSA 2016 annual conference in Phoenix and is accessible at: https://scisoc.confex.com/crops/2016am/webprogram/Paper100533.html
A summary of findings was later presented on the NDSU – Carrington REC blog at: https://www.ag.ndsu.edu/CarringtonREC/center-points/distillers-grains-impacted-yields-of-corn-and-spring-wheat-when-used-as-a-source-of-p
NDSU Carrington Research and Extension Center Annual report, 2018. https://www.ag.ndsu.edu/carringtonrec/documents/annual-reports/2018-annual-report
The authors are grateful to the North Dakota Corn Council, and North Dakota Agricultural Products Utilization Commission for funding the corn and wheat projects, respectively, and also to Tharaldson Ethanol (Casselton, ND) for supplying us with the distillers grains.
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