Submitted to: Humic Science and Technology Conference
Publication Type: Abstract Only
Publication Acceptance Date: March 14, 2012
Publication Date: N/A
Technical Abstract: Amino acids, amino sugars, carbohydrates, phenols, and fatty acids together comprise appreciable proportions of soil organic matter (SOM). Their cycling contribute to soil processes, including nitrogen availability, carbon sequestration and aggregation. For example, soil accumulation of phenols has been associated with soil carbon accumulation, inhibited nitrogen cycling, and diminished grain yield of paddy rice in the Philippines, Vietnam, Arkansas, and possibly India. In other settings, the roles of these biochemical classes in soil and crop performance were examined by measuring their contents in young, labile SOM fractions, as distinct from older SOM. An integrated procedure for extracting three physical and two chemical SOM fractions depicted seasonal flows of microbial versus plant-derived carbohydrates under cover cropping in an Iowa corn soybean field. This fractionation procedure also enabled early detection of changes in labile SOM during the transition from conventional to organic farming at two sites in southern Italy. Distinction of humic fractions based on their binding to soil calcium is one mode of separating young humic material from older humic material. This distinction guided carbon accumulation in soil macroaggregates of two Nebraska corn-soybean fields, and it distinguished humic material that is active in seasonal nitrogen cycling from material that is less active, both for paddy rice and corn-soybean systems. In the two projects completed to date, the five fractions represented only 25-35% of total soil carbon. An iron-bound humic acid fraction is now also being extracted.