The effect of waterlogging on phosphorus solubility caused by redox reaction in wetland soil of the Fraser Valley in British Columbia
Rupngam et al. 2022. The effect of waterlogging on phosphorus solubility caused by redox reaction in wetland soil of the Fraser Valley in British Columbia. CSSS-ASSW 2022, Soil Science for Sustainable Development May 23-27, 2022. Edmonton
The flood generated in some agricultural plots during fall and winter season in British-Columbia could modify the solubility of phosphorus (P). Althought the P is less mobile in soils, the risk of P loss to the environment would be expanded in high phosphorus soil. This study aims to evaluate the effects of the waterlogged soil in the high P soil on (i) the redox reaction which lead to the reduction of Fe3+ to Fe2+, (ii) the the solubility of P, and (iii) microbial activities in the wetland of the Fraser Valley in British Columbia. The soils were incubated for four months with 11 sampling dates (0, 3, 7, 14, 21, 28, 35, 49, 63, 90, and 120 days after incubation : DAI), three soil moisture regimes (field capacity, water saturation, and waterlogged), and two iron levels (iron addition and no iron addition). The results demonstrated that the redox potential decrease under waterlogged soil after 2 months of incubation (from 0.18 to 0.11 and to 0.05 V, at 0, 90, and 120 DAI respectively), involving in a reduction of the ferric to ferrous iron (1190 mg kg-1 of iron on average were reduced after 120 DAI) and an increase of soil pH (from 5.2 to 5.4, whereas this was decreased for soil at field capacity condition from 5.2 to 4.7). The water-extractable P (Pw) was 1.37 and 0.86 mg kg-1 higher under saturation and waterlogged soil respectively compared to the field capacity condition. This augmentation of soluble P was positively and significantly (P < 0.05) correlated to the degree of phosphate saturation (DPS), the dissolved organic carbon (DOC), the soil pH, the microbial biomass phosphorus, the CO2 and CH4 emission from soil surface. Moreover, we observed an increase of soluble P, iron, DOC, As, S, and Mn concentration in the water column after 120 days of incubation. These suggest that the temporarily waterlogged soils increase the solubility of P, which is governed by the DPS, the reduction reaction, and the microbial activities through the greenhouse gas emission. This also increase the metal concentration in the water column after four months of incubation. The study on enzyme activities and microbial diversities are necessary to better understand the process driving the solubility of P.