Location: Forage Seed and Cereal ResearchTitle: An examination of the role of biochar and biochar water-extractable substances on the sorption of ionizable herbicides in rice paddy soils
|HELMUS, RICK - University Of Amsterdam|
|KNICKER, HEIKE - Instituto De Recursos Naturales Y Agrobiologia De Sevilla (IRNAS-CSIC)|
|COX, LUCIA - Instituto De Recursos Naturales Y Agrobiologia De Sevilla (IRNAS-CSIC)|
|HERMOSIN, MARIA - Instituto De Recursos Naturales Y Agrobiologia De Sevilla (IRNAS-CSIC)|
|PARSONS, JOHN - University Of Amsterdam|
|KALBITZ, KARSTEN - University Of Amsterdam|
Submitted to: Journal of Environmental Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2019
Publication Date: 11/22/2019
Citation: Garcia-Jaramillo, M.N., Trippe, K.M., Helmus, R., Knicker, H.E., Cox, L., Hermosin, M.C., Parsons, J.R., Kalbitz, K. 2019. An examination of the role of biochar and biochar water-extractable substances on the sorption of ionizable herbicides in rice paddy soils. Journal of Environmental Management. 706. https://doi.org/10.1016/j.scitotenv.2019.135682.
Interpretive Summary: Biochar is a carbon-rich material that is added to soils for agricultural and environmental applications. Biochar can be used to address soil health deficiencies by increasing pH, increasing soil carbon, reducing metal toxicity, and improving water infiltration and retention. In soil, biochar can act similarly to activated charcoal and irreversibly bind agricultural chemicals. The binding of agrochemicals to biochar has cropping and environment consequences. For example, biochar can absorb pesticides, reducing their efficacy or preventing their transport in the environment. Understanding the mechanisms that drive biochar-agrochemical interactions can inform decisions regarding the use of biochar. In this study, we wondered if the water soluble portion of biochar played a role in the binding of azimsulfuron and penoxsulam, two chemicals commonly used to control weeds in the cultivation of rice. We learned that biochar influences the availability of these chemicals in soils collected from rice paddies. Our results also indicate that behavior of these herbicides is influenced by the amount and molecular composition of water soluble fraction of biochar, which can change with time and environmental exposure. These observations stress the importance of proper consideration of soil and biochar properties before their incorporation.
Technical Abstract: The application of biochar as soil amendment can increase concentrations of soil organic matter, especially water-extractable organic substances. Due to their mobility and reactivity, more studies are needed to address the potential impact of biochar water-extractable substances (BWES) on the sorption of pesticides, especially in soils that are periodically flooded. Two paddy soils (100 and 700 years of paddy soil development), unamended or amended with raw or washed biochar, were used to test the influence of BWES on the sorption behavior of the herbicides azimsulfuron (AZ) and penoxsulam (PE). Biochar sorption isotherms were nonlinear and resembled L-type isotherms, indicating certain specificity in the sorption of both herbicides. The depletion of polar groups in the BWES from the washed biochar, especially O- and N- containing components, modified the adsorption of AZ and PE to the soils, and it was attributed to ligand-exchange mechanisms. The adsorption of AZ increased when the younger soil (P100) was amended with raw biochar. In the older soil (P700), with lower dissolved organic carbon (DOC) content than P100, the adsorption of AZ increased regardless of whether biochar was raw or washed. The results of our study indicate that biochar influences the sorption of AZ and PE in paddy soils. Our results also indicate that sorption of these herbicides is influenced by the amount and molecular composition of BWES, which can change with time and environmental exposure. These observations stress the importance of proper consideration of soil and biochar properties before their incorporation into paddy soils.