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Title: Diffuse-Reflectance Mid-Infrared Spectral Properties of Soils under Alternative Crop Rotations in a Semiarid Climate

Author
item Calderon, Francisco
item Mikha, Maysoon
item Vigil, Merle
item Nielsen, David
item Benjamin, Joseph
item Reeves Iii, James

Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2011
Publication Date: 8/22/2012
Citation: Calderon, F.J., Mikha, M.M., Vigil, M.F., Nielsen, D.C., Benjamin, J.G., Reeves III, J.B. 2012. Diffuse-reflectance mid-infrared spectral properties of soils under alternative crop rotations in a semiarid climate. Communications in Soil Science and Plant Analysis. 42:17, 2143-2159.

Interpretive Summary: This study uses infrared spectroscopy to measure the quality of the soil organic matter in different dryland crop rotations in the Great Plains. Our results show that un-cultivated prairie soils not only have higher organic matter content, but that they also contain a different kind of organic carbon relative to the crop rotation soils. After 15 years under different crop rotations, the organic matter has similar chemical properties among the cropped soils. Grass plots within the crop rotation experiment are exhibiting higher organic matter relative to the cropped soils, but similar soil quality.

Technical Abstract: An Alternative Crop Rotations (ACR) experiment was designed to compare the traditional wheat-fallow rotation with more intensive no-till rotations in the Central Great Plains. In order to ascertain the effect of the different agronomic managements on soil quality, we carried out mid-infrared (MidIR) spectral interpretation of soils from 0-5 and 5-15 depths of selected ACR treatments as well an adjacent native prairie soil. Ashing and spectral subtraction shows that absorbance at 3700-2850 and 1700-1550 cm-1, indicates organic absorbance in these soils. After 15 years of the ACR experiment, prairie soils, with their higher C content, have different spectral properties from the cropped soils. Prairie soils have higher absorbance at 2950-2870 cm-1 and the 1230 cm-1 bands for aliphatic and aromatic CH. The soils from the two different depths had different spectral properties, with the 0-5 cm soils having stronger absorbance at the 1055 cm-1 carbohydrate band, at 1270-1460 cm-1 and at the 1730 cm-1 ester band. The 5-15 cm soils are characterized by higher absorbance at the clay hydroxyl band. Soil C and N correlated negatively with the 3700 cm-1 clay band, and the 1830 cm-1 quartz band, and correlated positively with the 2920 cm-1 due to aliphatic CH absorbance. Microbial biomass carbon was associated with absorbance at the 1650 cm-1 possibly due to absorption of microbial proteins.