Fertilisation of agricultural soils with municipal biosolids: Part 1- Glyphosate and aminomethylphosphonic acid inputs to Québec field crop soils

Abstract

Municipal biosolids (MBS) are suggested to be abundant, sustainable, inexpensive fertilisers, rich in phosphorus and nitrogen. However, MBS can also contain glyphosate and phosphonates that can degrade to AMPA. Glyphosate-based herbicides (HBG) are used in field crops all over the world. Most glyphosate generally degrades within a few weeks, mainly as aminomethylphosphonic acid (AMPA). AMPA is more persistent than glyphosate, and can accumulate from one crop year to the next. AMPA is phytotoxic even to glyphosate-resistant crops. The aims of this study were to assess whether applications of MBS significantly contribute to: 1) glyphosate and AMPA contents of agricultural soils, 2) trace metal elements contents, and 3) partial replacement of mineral fertilisation while maintaining similar yields. To this end, four experimental agricultural sites were selected in Québec (Canada). Soil samples (0-20 cm) were collected to estimate the as yet unmeasured contribution of BSM application to glyphosate and AMPA inputs in agricultural soils. MBS applied in 2021 and 2022 had mean concentrations of 0.69 ± 0.53 µg glyphosate/dry g and 6.26 ± 1.93 µg AMPA/dry g. Despite the presence of glyphosate and AMPA in MBS, monitoring of these two compounds in corn and soybean crops over two years showed no significant difference between plots treated with and without MBS applications. For the same site, yields measured at harvest were similar between treatments. MBS application could thus represent a partial alternative to mineral fertilisers for field crops, while limiting the economic and environmental costs associated with their incineration and landfilling. It is also an economic advantage for agricultural producers given the possibility of using fewer mineral fertilisers and therefore reducing the environmental impact of their use.HighlightsMunicipal biosolids (MBS) offer significant potential for fertilising field cropsMBS contain significant amounts of both glyphosate and AMPASoil chemistry and crop yields were followed in MBS treated and untreated plotsGlyphosate and AMPA contents in soil do not increase with MBS treatmentMBS are a good substitute for mineral fertilisers leading to similarly crop yieldsGraphical abstract