What Is the Agronomic Value of Corn Cobs? A Study Conducted in the North-Central Corn Belt.

Over the next several years producers and the bioethanol industry are challenged to develop a working relationship in which the producers are receiving adequate compensation for their commodities while maintaining the profitability of the industry.  There is currently limited information available on the amount of nutrients that will be removed from the soil resources if corn cobs are to become a feedstock for the industry.  In the short-term, producers want to know the increase in nutrients removal that would occur if cobs are to be utilized as a feedstock.  A limited field study was conducted to evaluate the amount of dry matter, and nutrients taken up in the cob compared to the rest of the above ground plant.  Random plant samples were collected from 53 different production fields in southeastern South Dakota and northwestern Iowa. The fields varied in soil type, agronomic management practices, and hybrid.  Plant samples were separated in to three components: grain, cobs, and residual biomass (stalks, leaves and hulks).  Once the samples were separated, dry weights were measured and chemical analysis was performed for several nutrients (carbon, nitrogen, phosphorus, potassium, calcium, magnesium, iron, and sulfur). On average less than 7% of the total for each nutrient was stored within the cob.  Removal of the cob would remove an additional 6.7 kg/ha of nitrogen, 0.38 kg/ha of phosphorus, and 4.5 kg/ha of potassium.  In the short-term it appears that additional removal of the cob might have limited impact on the soil environment, but additional long-term studies will need to be conducted to support this statement.