Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/13/2015
Publication Date: 6/20/2015
Publication URL: http://handle.nal.usda.gov/10113/63014
Citation: White Jr, P.M., Potter, T.L., Lima, I.M. 2015. Sugarcane and pinewood biochar effects on activity and aerobic soil dissipation of metribuzin and pendimethalin. Industrial Crops and Products. 74(2015):737-744. DOI: 10.1016/j.indcrop.2015.04.022
Interpretive Summary: Our work focused on how incorporation of biochar may impact the activity and soil dissipation rate of Sencor® and Prowl®, two soil-residual herbicides. Biochars produced by pyrolysis of sugarcane bagasse (350°C and 700°C) and pine wood (400°C) and are abbreviated BC350, BC700, and WC400, respectively. The biochars were mixed with a clay, a silt loam, and a loamy sand soil. Biochar additions doubled the soil organic carbon content. The BC350 significantly increased the time Sencor® resided in soil, when compared to the control. Both BC700 and WC400 had little impact on Sencor® losses. For Prowl®, a reverse trend was observed, as the BC750 and WC400 increased the residence time of the herbicide. In the loamy sand soil, the 1-4% biochar rate contributed to an increased trend in weed seed (palmer amaranth) emergence. At the 8% rate, palmer amaranth emergence was statistically higher than the control. In sum, how biochar impacted the fate of these herbicides depended on soil, herbicide, and biochar properties. These factors must be considered when evaluating use of these and other herbicides in biochar amended soils.
Technical Abstract: Biochars were produced by pyrolysis of sugarcane bagasse (350°C and 700°C) and pine wood (400°C) and are abbreviated BC350, BC700, and WC400, respectively. Metribuzin adsorption by batch equilibrium showed that BC700 had the greatest adsorption capacity followed by BC350 and WC400. The bagasse biochars were mixed with a clay and a silt loam soil and the pine wood biochar with a loamy sand soil and fortified with the metribuzin and pendimethalin. Biochar additions doubled the soil organic carbon content. The soils were incubated at 25°C in the dark and were extracted with methanol after 0, 7, 14, 21, 28, 42, 63, 86, and 111 days. Parent compounds and metribuzin degradates were analyzed in extracts by HPLC – mass spectrometry. Increases in the metribuzin DT50 were indicated for all soil-biochar combinations. BC350 had the greatest impact more than doubling the DT50 in the silt-loam soil. In contrast BC700 had minimal impact on the DT50 in the silt loam soil and contributed to a significant DT50 decrease in the clay. The metribuzin degradate, metribuzin-desamino, was detected at rates proportional to metribuzin dissipation. For pendimethalin, biochar additions increased DT50 in all soil-biochar combinations. In contrast to metribuzin, BC700 and W400 had the greatest impact with the BC700 increasing the DT50 by more than 2-fold. In the loamy sand soil, the 1-4% biochar rate contributed to an increased trend in palmer amaranth emergence. At the 8% rate, palmer amaranth emergence was statistically higher than the control (p=0.072). In sum, how biochar impacted the activity and dissipation of these herbicides depended on soil, herbicide, and biochar properties.