Effects of Short-Term Waterlogging on Soybean Nodule Nitrogen Fixation at Different Soil Reductions and Temperatures

Abstract

Short-term waterlogging often occurs in upland fields converted from paddies in Japan, since paddy fields have poor surface drainage and a high water table. The objective of this study was to clarify the effects of different durations of waterlogging (W) and waterlogging with soil reduction (WR) on soybean nitrogen fixation at different soil temperatures. Acetylene reduction activity (ARA) was reduced by W treatment for 3, 5 and 7 days (d), ARA was restored to the same level as in the control (C) at 3 days after the end of the treatment (DAT). However, ARA reduced by the WR treatment for 3, 5 and 7 d in a greenhouse was not restored. In the experiments under three soil temperature conditions (lower than 30ºC, around 34ºC and higher than 36ºC) and with two waterlogging durations (3 and 5d) in the growth chamber, ARA reduced by the W treatment was restored after the treatment irrespective of soil temperature and waterlogging duration whereas ARA reduced by WR was restored only after the short-term waterlogging at a low soil temperature. The nodule dry weight and respiration rate of the root system significantly decreased when ARA was greatly reduced. In addition, ARA at 3 DAT was positively correlated with stomatal conductance (SC) at 4 DAT. We concluded that the recovery of nodule nitrogen fixation from the reduction by waterlogging is strongly affected by the oxidation-reduction potential and temperature of the soil, and the nodule damage could be evaluated by SC.