Quantity and nature of water-extractable organic matter from sandy loam soils with potato cropping managements

Authors: He, Zhongqi; ZHANG, MINGCHU - University Of Alaska; ZHAO, AIQIN - University Of Alaska; Olanya, Modesto; Larkin, Robert - Bob; HONEYCUTT, C - Natural Resources Conservation Service (NRCS, USDA)

Submitted to: Agricultural & Environmental Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/3/2016
Publication Date: 8/25/2016
Citation: He, Z., Zhang, M., Zhao, A., Olanya, O.M., Larkin, R.P., Honeycutt, C.W. 2016. Quantity and nature of water-extractable organic matter from sandy loam soils with potato cropping managements. Agricultural and Environmental Letters. 1:160023-160029.

Interpretive Summary: Water-extractable organic matter (WEOM) is part of the soil labile organic matter components. In this work, we evaluated the level and nature of soil WEOM fractions from a long-term (6-year) potato crop rotation field experiment. Data indicated that a higher level of WEOM in continuous potato soil due to its recalcitrance and a high degree of humification. Two- and three-year crop rotations did not increase the level of WEOM, but increased the less humified portions. Irrigation increased the level of WEOM in crop rotation soils by stimulation of decomposition of non-potato crop residues. Soil improvement by composted manure addition increased not only WEOMr content, but also low molecular mass and less humified portions. Findings in this study contributed to the overall goal of the project, which is to enhance the sustainability of the potato industry in the Northeast U.S.A. This study also increased the general knowledge on how cropping management affects labile organic matter content and quality.

Technical Abstract: Water-extractable organic matter (WEOM) is part of the soil labile organic matter components. In this work, we evaluated the level and nature of soil WEOM from a long-term (6-year) potato crop rotation field experiment. The contents of water-extractable organic C (WEOC) were higher in continuous potato soils than in the 2-year and 3-year crop rotation soils except for those with soil improvement management (composted manure added). Irrigation increased the level of WEOM in crop rotation soils, implying that irrigation (soil water) promoted the decomposition of non-potato crop residues to WEOM. UV/visible and fluorescence parameters (SUVA254, SUVA280, E4/E6 and HIX) indicated that WEOM in continuous potato soil possessed a high degree of humification and crop rotation increased the aromatic and low molecular mass portions in WEOM. Compared to the corresponding rainfed samples, WEOM in most irrigated soils showed lower SUVA254 and SUVA280, but higher E4/E6 and HIX values, suggesting that WEOM in irrigated samples contained less aromatic but higher humified components. The effect of irrigation of the WEOM chemical nature was lower in the crop rotation soils probably due to the input of fresh WEOM from crop residues and composted manure.