Soil water extractable organic matter under long‐term dryland cropping systems on the Texas High Plains

Water extractable organic matter (WEOM) is critical for soil fertility because of its role as a readily available C substrate microbial metabolism. In the semi-arid Texas High Plains, dryland cropping systems are common limited precipitation and irrigation water. Little known about long-term effects on WEOM content composition, how these differ from native grassland. The objective this study was to use soils collected near Amarillo, TX, in 1977 2013 examine (72 yr total length) [continuous wheat wheat–fallow rotations] tillage methods (disk plow, stubble-mulch tillage, delayed tillage) characteristics, compared with cropped plots, water-extractable carbon (WEOC) concentrations, measure content, were depleted regardless or crop, reductions up 13% 60% 2013, grassland 2013. Other parameters changed over time, where had proportionally more aromatic, phenolic, lignin-like forms, attributed recently incorporated crop residues. contrast, (2013) contained functional groups (e.g., aliphatic, polysaccharide, phenol, etc.) humic-like substances than This suggests that led depletion stable, WEOM. Enhancement stocks sustainability Plains may require vigorous conservation currently used.