Spatial Control of Microbial Pesticide Degradation in Soil: A Model-Based Scenario Analysis

Abstract

Microbial pesticide degraders are heterogeneously distributed in soil. Their spatial aggregation at the millimeter scale reduces the frequency of degrader–pesticide encounter and can introduce transport limitations to pesticide degradation. We simulated reactive pesticide transport in soil to investigate the fate of the widely used herbicide 4-chloro-2-methylphenoxyacetic acid (MCPA) in response to differently aggregated distributions of degrading microbes. Four scenarios were defined covering millimeter scale heterogeneity from homogeneous (pseudo-1D) to extremely heterogeneous degrader distributions and two precipitation scenarios with either continuous light rain or heavy rain events. Leaching from subsoils did not occur in any scenario. Within the topsoil, increasing spatial heterogeneity of microbial degraders reduced macroscopic degradation rates, increased MCPA leaching, and prolonged the persistence of residual MCPA. In heterogeneous scenarios, pesticide degradation was limited by the spatial separation of degrader and pesticide, which was quantified by the spatial covariance between MCPA and degraders. Heavy rain events temporarily lifted these transport constraints in heterogeneous scenarios and increased degradation rates. Our results indicate that the mild millimeter scale spatial heterogeneity of degraders typical for arable topsoil will have negligible consequences for the fate of MCPA, but strong clustering of degraders can delay pesticide degradation.

Degradation strategies of pesticide residue: From chemicals to synthetic biology

“…Different tools and processes should be designed for the purpose of the consortium [ 22 , 114 ]. In addition, the appropriate method design needs to be based on sufficient data support; the simulation and analysis of environmental conditions will provide a basis for the expansion of synthetic biology application in pesticide degradation [ 121 , 122 ]. All in all, synthetic biological methods will head in a more multi-dimensional direction, combining chemical and biological degradation methods, breaking technical barriers and species restrictions to achieve a more integrated system.…”

Microbial degradation of plant toxins

“…Since the emerging trend towards limiting the usage of pesticides in agriculture, PSMs, and their insecticide and herbicide properties have gained more interest. Using PSMs to restore sustainable crop protection could be thus an alternative solution to pesticides, which nowadays are less effective and contribute to pollution (Ahmad et al, 2022; Almeida et al, 2017; Gangola et al, 2022; Itoh et al, 2014; Itoh et al, 2018; Schwarz et al, 2022; Singh & Singh, 2016; van den Bosch & Welte, 2017). Therefore, obtaining more insights into the microbial degradation of PSMs has great value to both agriculture and bioremediation.…”

Temperature and soil moisture change microbial allocation of pesticide‐derived carbon

“…Pesticide residues in European arable soils have become an environmental threat of great concern (Silva et al, 2019). Microbial degradation is the most important process to reduce this pesticide contamination (Schwarz et al, 2022), whereby degradation rates depend primarily on soil temperature (Helweg, 1993). How accessible the pesticide residues are to microbial degradation is influenced by the soil moisture content (Schroll et al, 2006).…”