SOIL MANAGEMENT SYSTEMS FOR DRYLAND AND IRRIGATED CROPPING SYSTEMS
Location: Agroecosystem Management Research
Title: Corn cob residue carbon and nutrient dynamics during decomposition
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 11, 2011
Publication Date: May 25, 2011
Citation: Wienhold, B.J., Varvel, G.E., Jin, V.L. 2011. Corn cob residue carbon and nutrient dynamics during decomposition. Agronomy Journal. 103:1192-2297. Available: doi:102134/agronj2011.0002.
Interpretive Summary: Crop residue has been identified as a feedstock for biofuel production. Residue performs a number of soil conservation functions and removing it from the field may reduce these beneficial functions. The cob component of corn residue comprises one-fifth of the residue, can potentially be collected during grain harvest, and is being considered as a feedstock. A study was conducted to determine how cob harvesting may affect nutrient availability to the following crop. Cobs decomposed more quickly when buried than on the soil surface. Fertilizer nutrients such as nitrogen, phosphorus, and sulfur were retained while potassium was lost from the residue as it decomposed. Other minor nutrients such as calcium, magnesium, zinc, manganese, and copper accumulated in the residue. With the exception of potassium, removing cobs for use as a feedstock should not affect nutrient availability to the following crop.
The cob fraction of corn (Zea mays L.) residue has characteristics that reduce concerns associated with residue removal making it a potential biofuel feedstock. The contribution the cob fraction makes to soil C and nutrient dynamics is unknown. A litterbag study was conducted in no-tillage plots under irrigated and rainfed conditions in eastern Nebraska. Litterbags containing cob residue were placed on the soil surface or vertically in the 0- to 10-cm soil depth following grain harvest and collected after 63, 122, 183, 246, 304, and 370 days. Samples were analyzed for dry matter, C, N, P, K, S, Ca, Mg, Fe, Mn, and Zn. Dry matter loss was greater for buried (59% loss at the rainfed site vs. 64% at the irrigated site) than surface residue (49% loss at the rainfed site vs. 42% at the irrigated site). Residue N, P, S, content did not change over the duration of the study suggesting that these nutrients would play a limited role in nutrition for the subsequent crop. Residue K content declined exponentially over the duration of the study suggesting that cob residue K would be available to the subsequent crop. Residue Ca, Mg, Zn, Fe, Mn, and Cu content increased during the study representing immobilization during decomposition. With the exception of K, nutrients contained in the cob fraction are immobilized during decomposition the year following harvest and should play a minor role in mineral nutrition of the subsequent crop.