Sequence and preference in the use of electron acceptors in flooded agricultural soils
Ab s t r a c t. Specifically, it was tested whether the presence of O 2 in the headspace modified the sequence and preference of electron acceptor use under hypoxic conditions after prolonged drought in arable soils. This laboratory study was conducted in order to examine the use of electron acceptors: oxygen (O 2 ), nitrate (NO 3¯) and nitrous oxide (N 2 O), during aerobic and anaerobic respiration (denitrification). Agricultural soils (Typic Dystrudepts) classified as sandy, silty and loamy
... , silty and loamy soils from arable top soils (0-30 cm) were used in the study. The change of oxidation states of different chemical species in the soil affected the use of electron acceptors during denitrification. The use of O 2 , NO 3¯ and net N 2 O use was gradual and differed greatly among the soils. Furthermore, microorganisms were shown to be able to use all three investigated electron acceptors simultaneously, but with clearly visible preferences. The rate of electron acceptor use per day differentiated the investigated soils into a few different groups. Overall, the results of this study indicated that N 2 O was a more preferable electron acceptor than NO 3¯ when O 2 was present in the headspace for the most investigated soils. Moreover, a correlation existed between the final electron acceptor use and particle-size distribution and the native organic C content (C org ). The rate of electron acceptor use per day calculated for O 2 , NO 3¯ and N 2 O may provide very important information for distinguishing the preference of electron acceptor use during aerobic and nitrate respiration in agroecosystems under hypoxic conditions after prolonged drought for different kinds of electron acceptor.