Modeling water and isoproturon dynamics in a heterogeneous soil profile under different urban waste compost applications

Abstract

International audienceCompost amendments and tillage practices can modify soil structure and create heterogeneities at the local scale. Tillage affects soil physical properties and consequently water and solute transport in soil, while compost addition to soil influences pesticide sorption and degradation processes. Based on the long-term field experiment QualiAgro (a INRA–Veolia partnership), a modeling study was carried out using HYDRUS-2D to evaluate how two different compost types combined with the presence of heterogeneities due to tillage affect water and isoproturon dynamics in soil compared to a control plot. A municipal solid waste compost (MSW) and a co-compost of sewage sludge and green wastes (SGW) have been applied to experimental plots. In each plot, wick lysimeters, TDR probes, and tensiometers were installed to monitor water and solute dynamics. In the plowed layer, four zones differing in their structure were identified: compacted clods, non-compacted soil, interfurrows, and the plow pan. From 2004 to 2010, the unamended control (CONT) plot had the largest cumulative water outflow (1388 mm) compared to the MSW plot (962 mm) and SGW plot (979 mm). After calibration, the model was able to describe cumulative water outflow for the whole 2004–2010 period with a model efficiency value of 0.99 for all three plots. The CONT plot had the largest isoproturon cumulated leaching (21.31 μg) while similar cumulated isoproturon leaching was measured in the SGW (0.663 μg) and MSW (0.245 μg) plots. The model was able to simulate isoproturon leaching patterns except for the large preferential flow events that were observed in the MSW and CONT plots. The timing of these preferential flow events could be reproduced by the model but not their magnitude. Modeling results indicate that spatial and temporal variations in pesticide degradation rate due to tillage and compost application play a major role in the dynamics of isoproturon leaching. Both types of compost were found to reduce isoproturon leaching on the 6 year duration of the experiment

Modeling Copper and Cadmium Mobility in an Albeluvisol Amended with Urban Waste Composts

“…This method was used to distinguish between different soil structures present in the tilled layer: the Γ structure—corresponding to macroporous, uncompacted soil; the Δ structure—corresponding to compacted clods; the interfurrows (IFs)—formed between the furrows created by the moldboard plow; and the plow pan (PP)—corresponding to a compacted layer created by long‐term plowing to the same depth. More information about structure types and profile geometry can be found in Filipović et al (2014, 2016). The soil profile geometry of all three plots was precisely reproduced into the HYDRUS‐2D model domain (Fig.…”

“…The soil was systematically sampled at the nodes of a 4‐cm rectangular grid (0.36‐m height, 1‐m width). Hydraulic properties, TDR and tensiometer data, and lysimeter outflow volumes were presented and discussed by Filipović et al (2014, 2016).…”

“…In this study, field measurements and modeling were used to evaluate and interpret the differences found by Cambier et al (2014) in the leaching of Cd and Cu below the plow layer of cultivated plots periodically amended with different urban waste composts. Numerical modeling was performed on the same field site using HYDRUS‐2D to estimate the movement of Cd and Cu from compost incorporated in the tilled layer following the method proposed by Filipović et al (2016), which was previously used to simulate water dynamics in compost‐amended plots. A similar water flow and Br transport modeling approach was first used by Coquet et al (2005) to account for soil heterogeneity originating from plowing and compaction by agricultural operations.…”

Representation of Plot‐Scale Soil Heterogeneity in Dual‐Domain Effective Flow and Transport Models with Mass Exchange

“…1) was applied here to arable soils in which soil cultivation has led to more or less compacted regions with highly contrasting hydraulic properties. At the plot scale (i.e., an area of 4–20 m 2 ), these heterogeneities could be spatially described in detail and included in 2D or 3D single‐domain numerical models (Coquet et al, 2005b; Filipović et al, 2016). For the field scale, the explicit consideration of such details is mostly not possible, and approaches for simplification are required.…”

“…Although the implementation of a second domain in transport models can be challenging, it can have a large importance in describing nonequilibrium solute transport such as the pesticide fate discussed by Pot et al (2005). For example, Filipović et al (2016) simulated long‐term wick‐lysimeter water outflows from a heterogenous soil profile amended with compost using the 2D_SP model with NSE = 0.99; however, large peaks of isoproturon ( N , N ‐dimethyl‐ N ′‐[4‐(1‐methylethyl)phenyl]urea) pesticide observed just after the application could not be simulated using the same single‐porosity approach.…”