Alum reduced phosphorus release from flooded soils under cold spring weather conditions

Abstract

The effectiveness of amendments such as alum [Al2(SO4)3·18H2O] in reducing phosphorus (P) loss to floodwater has been reported under summer conditions and laboratory‐controlled environments, but not under actual spring weather conditions in cold climate regions with high diurnal temperature variations when potential for P losses is high. The effectiveness of alum in reducing P release under Manitoba spring weather conditions was evaluated in a 42‐day experiment using 15‐cm soil monoliths from eight agricultural soils, which were unamended or alum‐amended (5 Mg ha−1) and flooded to a 10‐cm head. Dissolved reactive P (DRP) concentrations and pH of porewater and floodwater were determined on flooding day and every 7 days after flooding (DAF). Porewater and floodwater DRP concentrations in unamended soils increased 1.4‐ to 4.5‐fold, and 1.8‐ to 15.3‐fold, respectively, from 7 to 42 DAF. In alum‐amended soils, DRP concentrations averaged across soils was 43%–73% (1.0–2.0 mg L−1) lower in porewater, and 27%–64% (0.1–1.2 mg L−1) lower in floodwater than unamended soils during the flooding period. The reduction of DRP by alum was more pronounced under high fluctuating diurnal spring air temperature than with controlled air temperature (4°C) in a previous similar study. Acidic pH in porewater and floodwater due to alum did not persist over 7 days. This study showed that alum application is a viable option in reducing P released to floodwater in agricultural soils of cold regions where flooding‐induced P loss is prevalent in the spring.

Phosphorus fractions and speciation in an alkaline, manured soil amended with alum, gypsum, and Epsom salt

“…The amendments were applied to the soil surface in the fall of 2020 prior to snowfall at a rate equivalent of 2.5 Mg ha −1 and incorporated within 0–5 cm. The rate of amendment application was decided based on previous literature, with laboratory and field studies showing that rates between 2.2 and 5 Mg ha −1 are effective in reducing P loss from soils (Lasisi, Weerasekara, et al., 2023; Vitharana et al., 2021; Watts & Torbert, 2016). A runoff box was installed in each plot to collect the snow over the winter season.…”

“…, and ferric chloride (FeCl 3 ) significantly reduced P release from most soils, with the effectiveness depending on the soil, amendment type and rate, and flooding time Kumaragamage et al, 2022;Van et al, 2022;Vitharana et al, 2021). Using intact soil columns placed outside during the spring snowmelt period, Lasisi, Weerasekara, et al (2023) reported that alum amendment reduced P release from soils to floodwater by 27%-64%. A recent field study conducted under Canadian prairie field conditions reported a decrease in dissolved reactive phosphorus (DRP) loads in snowmelt runoff with fall application of alum, gypsum, or Epsom salt to field plots.…”

“…Using intact soil columns placed outside during the spring snowmelt period, Lasisi, Weerasekara, et al. (2023) reported that alum amendment reduced P release from soils to floodwater by 27%–64%. A recent field study conducted under Canadian prairie field conditions reported a decrease in dissolved reactive phosphorus (DRP) loads in snowmelt runoff with fall application of alum, gypsum, or Epsom salt to field plots.…”