NITRIFICATION UNDER AND AFTER ALFALFA, BROME, TIMOTHY, AND WESTERN RYE GRASS: IV. OXIDATION-REDUCTION POTENTIALS AND CARBON DIOXIDE PRODUCTION

Changes in the redox potentials of the soils and crop residues were caused mainly by the action of micro-organisms. No relation between the potential measurements and the yield or composition of the crops in the field could be demonstrated. All four forage plants have some fraction that was responsible for a marked drift in potential, but which disappeared early in the process of decomposition.The greatest production of carbon dioxide occurred in soils under the hay crops, and it decreased with lapse of time after breaking. The production was greatest under and after alfalfa followed by brome. When the composition of the crop residues is taken into account, a relation between the carbon dioxide production and nitrate production can be demonstrated. The carbon dioxide production of decomposing residues decreases rapidly from a high initial value, giving further evidence of the presence of a readily decomposable constituent.