Effects of organic matter, moisture content and other environmental factors on denitrification in topsoils of an upland field

Effects of various environmental factors on the denitrification process in topsoils of an upland field were investigated. Denitrification was estimated from the evolution of N₂O in the presence of C₂H₂. The N₂O evolution from the soils under anaerobic conditions was markedly stimulated by the addition of glucose, but only slightly by that of nitrate. The denitrification in the soils was apparently limited by the supply of organic matter which can serve as effective electron donor. Denitrification hardly occurred when the soils with a moisture content less than 60% of the maximum water-holding capacity were exposed to the air. However, denitrification did occur after a time lag of 3 to 4 days at 12°C, 1 to 2 days at 20°C, and 0.5 day at 30°C, when the soils were water-logged. The denitrification capacity in a field cropped with maize was higher than that in an un-cropped field, the highest capacity being found in summer in the cropped field. This finding may result from the development of the maize rhizosphere where denitrification process is active. Experimental evidence supporting this assumption was presented.