Spot Spraying Reduces Herbicide Concentrations in Runoff

Abstract

Rainfall simulator trials were conducted on sugar cane paddocks across dry-tropical and subtropical Queensland, Australia, to examine the potential for spot spraying to reduce herbicide losses in runoff. Recommended rates of the herbicides glyphosate, 2,4-D, fluoroxypyr, atrazine, and diuron were sprayed onto 0, 20, 40, 50, 70, or 100% of the area of runoff plots. Simulated rainfall was applied 2 days after spraying to induce runoff at one plant cane and three ratoon crop sites. Over 50% of all herbicides were transported in the dissolved phase of runoff, regardless of the herbicide's sediment-water partition coefficient. For most sites and herbicides, runoff herbicide concentrations decreased with decreasing spray coverage and with decreasing herbicide load in the soil and cane residues. Importantly, sites with higher infiltration prior to runoff and lower total runoff had lower runoff herbicide concentrations.

Effects of agricultural land management changes on surface water quality: A review of meso-scale catchment research

“…Agricultural management practices that can effectively mitigate against on and offfarm surface water quality degradation have been demonstrated at field (Smith et al, 2001;Melland et al, 2016;), hillslope (Freebairn et al, 2009;Sousa et al, 2013) and micro catchment scales (McDowell et al, 2009;Tomer et al, 2014). In contrast, the effectiveness of farm practice change for water quality improvement at larger scales is less clear (Fenton et al, 2011;Vero et al, 2017).…”

Glyphosate and aminomethylphosphonic acid (AMPA) behavior in loess soils and off‐site transport risk assessment

“…Although glyphosate and AMPA adsorb strongly to soil particles, research on their transport by water erosion during rainfall events has focused mostly on their content in runoff water (Daouk et al, 2013;Coupe et al, 2012;Birch et al, 2011;Gregoire et al, 2010;Warnemuende et al, 2007;Siimes et al, 2006). Only recently, more attention has been paid to their particle-bound transport with runoff (Melland et al, 2016;Napoli et al, 2016;Yang et al, 2015a;Yang et al, 2015b). Our study indicates that the contribution of total particlebound transport was much higher than the total water-dissolved transport, particularly for T2.…”

“…There are some studies related to the transport of glyphosate and AMPA by water erosion, however most of them focused only on the occurrence of these compounds in the water phase (runoff water), neglecting the particle phase (Daouk et al, 2013;Birch et al, 2011;Gregoire et al, 2010;Warnemuende et al, 2007;Siimes et al, 2006). Although glyphosate and AMPA adsorb strongly to soil particles and tend to concentrate mostly in the very top surface layer, only recently studies have focused in their particle-bound transport with runoff as well (Melland et al, 2016;Napoli et al, 2016;Yang et al, 2015a;Yang et al, 2015b). Moreover, all studies on water erosion have had their main focus on the potential contamination risk of aquatic systems, disregarding their off-site transport to adjacent fields.…”

“…Although various studies have assessed the off-target transport of glyphosate and AMPA during rainfall events (Melland et al, 2016;Sasal et al, 2015;Daouk et al, 2013;Peruzzo et al, 2008), their transport to adjacent fields is normally disregarded. However, as shown in this study, the transport of sediment to adjacent areas can be a source of pollution.…”

“…As referred in chapter 1, most studies investigating the off-target transport of glyphosate and AMPA with water erosion focused only on the concentration of these compounds in the water phase (Daouk et al, 2013;Birch et al, 2011;Gregoire et al, 2010;Warnemuende et al, 2007;Siimes et al, 2006), while just a few recent studies contemplated the particlebound phase as well (Melland et al, 2016;Napoli et al, 2016;Yang et al, 2015a;Yang et al, 2015b).…”