Impact of Plant-Based Amendments on Water-Soluble Nitrogen Release Dynamics in Cultivated Peatlands

Abstract

Drained cultivated peatlands have been an essential agricultural resource for many years. To slow and reduce the degradation of these soils, which increases with drainage, the use of plant-based amendments (straw, wood chips, and biochar) has been proposed. Literature on the effects of such amendments in cultivated peatlands is scarce, and questions have been raised regarding the impact of this practice on nutrient cycling, particularly nitrogen (N) dynamics. By means of a six-month incubation experiment, this study assessed the effects of four plant-based amendments (biochar, a forest mix, willow, and miscanthus) on the release kinetics of water-soluble N pools (mineral and organic) in two histosols of differing degrees of decomposition (Haplosaprist and Haplohemist). The amendment rate was set at 15 Mg ha−1 on a dry weight basis. The N release kinetics were significantly impacted by soil type and amendment. Miscanthus and willow were the amendments that most reduced the release of soluble organic N (SON) and mineral N (minN). The addition of plant-based amendments reduced the total amount of released N pools during the incubation (cumulative N pools) by 50.3 to 355.2 mg kg−1, depending on the soil type, the N pool, and the type of amendment. A significant relationship was found between microbial biomass N, urease activity, and the cumulative N at the end of the incubation. The results showed that the input of plant-based amendments in cultivated peatland decreases N release, which could have a beneficial impact by decreasing N leaching; however, it could also restrict crop growth. Further research is needed to fully assess the impact of such amendments used in cultivated peatlands on N and on C fluxes at the soil–plant and soil–atmosphere interfaces to determine if they constitute a long-term solution for more sustainable agriculture.

Soil C, N and P bioavailability and cycling following amendment with shrub willow chips

“…The immobilization of soil mineral N following incorporation of willow chip corroborates previous findings (Holtz et al 2004;Gebhardt et al 2017;Espinosa et al 2020;Bourdon et al 2021;Dessureault-Rompré et al 2022;Marmier et al 2022). This N immobilization implies that willow chip addition can potentially mitigate nitrate availability for leaching, especially after potato harvest when high residual nitrate coexists with excessive moisture (Homyak et al 2008;Moorman et al 2010;Li et al 2013;Marmier et al 2022).…”

“…The immobilization of soil mineral N following incorporation of willow chip corroborates previous findings (Holtz et al 2004;Gebhardt et al 2017;Espinosa et al 2020;Bourdon et al 2021;Dessureault-Rompré et al 2022;Marmier et al 2022). This N immobilization implies that willow chip addition can potentially mitigate nitrate availability for leaching, especially after potato harvest when high residual nitrate coexists with excessive moisture (Homyak et al 2008;Moorman et al 2010;Li et al 2013;Marmier et al 2022). However, this mineral N immobilization may be short-lived as demonstrated by AEMs where AEM nitrate fluxes were strongly lower in plots amended with willow chip than in the unamended control during the first winter but comparable fluxes among treatments were observed in the second winter.…”

“…The addition of shrub willow (Salix spp.) chips to soils may mitigate nitrate leaching by immobilizing mineral N during fall and winter and enhance soil properties such as soil aggregate stability (Marmier et al 2022;Nyiraneza et al 2022).…”

“…The impact of wood chips on soil N immobilization is inconsistent in the literature. Some studies observed N immobilization following wood chip applications (Mackensen et al 2003;Holtz et al 2004;Gebhardt et al 2017;Espinosa et al 2020;Bourdon et al 2021;Dessureault-Rompré et al 2022;Marmier et al 2022). Others found no N immobilization (Burgess et al 2002;Tahboub et al 2007).…”

Mitigating CO2 emissions from cultivated peatlands: Efficiency of straws and wood chips applications in maintaining carbon stock in two contrasting soils

“…This strategy showed promising potential in preserving cultivated peatland C stock in C projection studies (32,33). This strategy could also potentially compensate for soil subsidence (34), reduce nutrient loss (35,36), and maintain (and restore) soil porosity and hydraulic conductivity (37)(38)(39). However, several factors need to be further investigated to help develop and implement effective organic amendment programs on these soils.…”