Cob Characteristics in Irrigated Central Great Plains Studies

Authors: Halvorson, Ardell; Johnson, Jane

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/24/2008
Publication Date: 3/4/2009
Citation: Halvorson, A.D., Johnson, J.M. 2009. Cob Characteristics in Irrigated Central Great Plains Studies. Agronomy Journal. 101:390-399.

Interpretive Summary: Escalating fossil fuel cost and concern over global climate change have accelerated interest in cellulosic feedstocks, such as corn cobs, for liquid fuel production. We summarized available cob data from several recent N fertility field studies in the Central Great Plains that was collected from two locations in Colorado and two in Texas that had multiple N fertilizer treatments, varying tillage systems, and very different growing seasons. All studies were irrigated so differences in (1) cob yield to grain yield, (2) cob yield to total corn residue production, and (3) cob N and C uptake were not due to water stress. Cobs accounted for 13 to 23% of stover biomass with an overall average of 16.8% for all locations, N rates, and years. Harvesting only cobs would leave the remaining stover in the field for erosion control and to provide biomass input for soil organic matter. The N concentration in cobs ranged from 2.65 to 5.19 g kg-1 with an overall average of 3.77 g kg-1. The relationship between final grain yield at 155 g kg-1 water content and oven-dry cob yield was linear (r2=0.75) such that cob yield increased 95.5 kg ha-1 for each 1 Mg ha-1 increase in grain yield. This study provides basic information on cob yield and quality for agronomists and will be useful for determining the feasibility of harvesting corn cobs as a cellulosic feedstock.

Technical Abstract: Escalating fossil fuel cost and concern over global climate change have accelerated interest in cellulosic feedstocks for liquid fuel production. One feedstock being evaluated is corn (Zea mays L.) cobs, but little information is available on this plant organ. Our objective was to compile and summarize available cob data from several recent field studies in the Central Great Plains. Data were collected from two locations in Colorado and two in Texas that had multiple N fertilizer treatments, varying tillage systems, and very different growing seasons. All studies were irrigated so differences in (1) cob yield to grain yield, (2) cob yield to total corn residue production, and (3) cob N and C uptake were not due to water stress. As a fraction of stover biomass, cobs accounted for 130 to 230 g kg-1 (13 to 23%) with an overall average of 168 g kg-1 (16.8%) for all locations, N rates, and years. Harvesting only cobs would leave the remaining stover in the field for erosion control and to provide biomass input for soil organic matter. The N concentration in cobs ranged from 2.65 to 5.19 g kg-1 with an overall average of 3.77 g kg-1. The relationship between final grain yield at 155 g kg-1 water content and oven-dry cob yield was linear (r2=0.75) such that cob yield increased 95.5 kg ha-1 for each 1 Mg ha-1 increase in grain yield. This study provides basic information on cob yield and quality for agronomists and will be useful for determining the feasibility of harvesting corn cobs as a cellulosic feedstock.