Dynamics of Glyphosate and Aminomethylphosphonic Acid in Soil Under Conventional and Conservation Tillage

Laura Carretta,Giuseppe Zanin,Roberta Masin,Alessandra Cardinali,Andrea Onofri

doi:10.1007/s41742-021-00369-3

Laura Carretta, Giuseppe Zanin + Show 3 more

Open Access

https://doi.org/10.1007/s41742-021-00369-3

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Abstract

This study investigates the adsorption and dissipation of glyphosate and the formation/dissipation of AMPA in non-tilled (NT) and conventionally tilled (CT) soil at 0–5 and 5–20 cm depth. Glyphosate adsorption was mainly related to the different NT and CT soil properties (clay and amorphous Al oxides), whereas an effect of the soil management could not be identified. Glyphosate dissipation was initially fast, and it slowed down later. The initial glyphosate concentration in NT soil at 0–5 cm was significantly lower than the dose applied due to the interception by the weeds and crop residues. AMPA began to form early after treatment and persisted longer than glyphosate. The DT50 range was 8–18 days for glyphosate and 99–250 days for AMPA. Longer glyphosate and AMPA DT50 were observed in NT soil compared to CT soil but, for glyphosate, the difference was significant only at 5–20 cm. Higher glyphosate and AMPA concentrations were detected in NT than in CT soil at the end of the study at 0–5 cm. The differences in glyphosate and AMPA DT50 and persistence were mainly attributable to the influence of different NT and CT soil characteristics. However, other factors could have contributed to the different glyphosate and AMPA dynamics between the soils, like glyphosate wash-off from crop residues on NT soil with the rainfall, the delayed glyphosate return to the soil by weed root exudation or weeds decomposition, and the NT soil compaction which may have reduced the microbial degradation of glyphosate at low concentrations.Graphic abstract

Highlights

Glyphosate (N-phosphonomethylglycine) is a non-selective, systemic, broad-spectrum, post-emergence herbicide
This study only partially answered the initial question, which aimed to investigate whether the no-tillage regime affected the dynamics of glyphosate and Aminomethylphosphonic acid (AMPA) in the soil compared to the conventional tillage
The glyphosate and AMPA dynamics in NT and conventionally tilled (CT) soils were primarily influenced by the intrinsic characteristics of the two soils, which were different despite their proximity

Summary

Introduction

Glyphosate (N-phosphonomethylglycine) is a non-selective, systemic, broad-spectrum, post-emergence herbicide. Its applications include weed control on transgenic glyphosateresistant crops, pre-harvest desiccation of cereals and total weed control in agricultural fields. It is the most used herbicide worldwide, with an estimated use of 826 million kg in 2014 (Benbrook 2016). Some of the factors influencing the fate of glyphosate in the soil are related to the intrinsic properties of the herbicide (e.g., molecular structure, adsorption, solubility, and persistence), whereas others depend on the physicochemical and biological characteristics of the soil (e.g., organic carbon content, pH, moisture, microbial biomass, pore connectivity, clay fraction, and cation exchange capacity) (Okada et al 2016; Soracco et al 2018). The strong adsorption tendency of glyphosate can lower the potential to contaminate surface waters or groundwater, but it contributes to the accumulation of glyphosate in soil (Gimsing et al 2004a; Vereecken 2005; Sidoli et al 2016)

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