Submitted to: Pest Management Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/21/2013
Publication Date: 5/1/2013
Citation: Camargo, E.R., Senseman, S.A., Haney, R.L., Guice, J.B., McCauley, G.N. 2013. Soil residue analysis and degradation of saflufenacil as affected by moisture content and soil characteristics. Pest Management Science. DOI: 10.1002/ps.3494. Interpretive Summary: Results from this study indicated that the ability of soil microbes to break down the herbicide saflufenacil is changed by cropping system used by the producer, and flooded vs. non-flooded conditions under 4 different soil types. Saflufenacil persistence in the environment was 2 to 3 times longer under flooded conditions for most of the soil series than non-flooded soils due to reduced soil microbial activity under flooded systems. Soil microbes require oxygen to operate at high metabolic rates, and flooded conditions limit oxygen to the soil. The half-life was less than 80 days for the combination of soils and moisture treatments, meaning the herbicide is effectively broken down by the soil microbes and should not impose an environmental problem in soil. An effective method to extract saflufenacil from soil samples was also developed to perform the experiment using an accelerated solvent extraction technique.
Technical Abstract: The objective of this study was to evaluate saflufenacil degradation and persistence in soils from rice regions under field capacity (non-flooded) and saturated (flooded) conditions. Saflufenacil dissolved in acetonitrile was added into pre-incubated samples at the rate of 2000 g ha-1. The amount of water added in the field capacity and saturation treatments was determined using a water retention curve. Microbial respiration was determined hourly for 30 days. Degradation rates were obtained from samples incubated at 24.8 C (± 0.5) in the dark from 0 to 45 days. An accelerated solvent extraction method was developed and used to extract saflufenacil from samples. Carbon mineralization was higher under field capacity conditions. Half-life averaged among soils was 59 and 33 days for saturated and field capacity, respectively. Saflufenacil persistence in the environment was 2 to 3 times longer under flooded conditions for most of the soils studied.