Reducing Herbicide and Veterinary Antibiotic Losses from Agroecosystems Using Vegetative Buffers

1. Reducing Herbicide and Veterinary Antibiotic Losses from Agroecosystems Using Vegetative Buffers R. N. Lerch1, C. H. Lin2, K. W. Goyne3, and H. E. Garrett2 1USDA-ARS, Cropping Systems and Water Quality Research Unit, Columbia, MO 2 Center for Agroforestry, University of Missouri 3Department of Soil, Environmental and Atmospheric Sciences, University of Missouri • Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

2. Rationale and Objectives • Rationale: • The ability of vegetative buffer strips (VBS) to reduce the transport of herbicides and veterinary antibiotics (VAs) has not been evaluated for high runoff potential soils such as those in the Central Claypan Region of northeastern Missouri. • Data to needed to support design criteria for implementation relative to contaminant of interest, choice of grass species, and buffer width • Objectives: • 1) To compare the effectiveness of three grass buffer treatments in reducing herbicide and VA loadsin surface runoff from a claypan soil • 2) To establish design criteria, relative to grass buffer widths, for estimating compound-specific load reductions using regression relationships. • 3) Evaluate the effect of season (spring, summer, fall) on VBS performance • Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

3. Materials and Methods Experimental Design Slope (4.9%) T1 T2 T3 T4 • Plot Layout • Mexico silt loam, 5% slope, eroded • Twelve 1.5 m by 16 m plots (4 treatments replicated 3 times) • Grass treatments: • Tall fescue (TF); • Tall fescue with a switchgrass hedge (Hedge + TF) • Native warm-season grasses (mainly eastern gamagrass and switchgrass) (Native) • Continuous cultivated fallow (Control) • Buffer width • Runoff collectors at: -1 m; 1 m, 4m, and 8m • Herbicides and VAs (rate, kg/ha) • Atrazine (2.2), glyphosate (1.5), and metolachlor (1.7) • Tylosin(4.65) and sulfamethazine (4.29), and Enrofloxacin (4.65) Tilled Area Tilled Area Tilled Area Tilled Area 8 m 1.0 m Fescue Native Fescue Tilled Area 8 m 4 m 1.5 m Switchgrass hedge width is 0.7 m Runoff sampling troughs

4. Materials and Methods Experimental Design – Grass Treatments Control Tall Fescue Hedge + Tall Fescue Native 8 M 4 M 1 M -1 M Source Area • Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

5. Materials and Methods Experimental Design • Plot Preparation • 1.5 m by 8 m area above the VBS was roto-tilled to ~10 cm (source area) • Plots brought to saturation 24 hours before runoff collection • Herbicides and VAs broadcast with a backpack sprayer 16 hours before runoff collection (not incorporated) • Runoff Collection • Runoff generated by a rainfall simulator at a rate of ~5 cm/hr • Samples collected beginning with initiation of flow at the 8 m sampler • Collected every 10 minutes for 60 minutes; composited to create one sample for each buffer width (i.e, -1, 1, 4, and 8 m) • Sample Analysis • Herbicides: water and sediment analyzed • VAs: only water analyzed • Experiments conducted from 2004 to 2010; pooled data from the summers of 2004 and 2006 are presented (VAs in 2006 only). • Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

6. Materials and Methods Computations and Statistics • Relative Load • Load = concentration (C) X flow (Q) for each buffer width. • Normalized Load = contaminant mass at each sampling position normalized to the total mass at the -1m samplers (input) • Statistics • 2-way ANOVA • Factors – grass species and buffer width • Significance level, α = 0.10 • F-LSD0.1 for mean comparisons • Correlated relative load reduction to buffer width • General form of the 1st-order decay equation: y = a + be-kx -1m (Input) 1m 4m 8m Q1 Q2 Q3 Q4 X X X X C1 C2 C3 C4 M1 M2 M3 M4 M1/M1 M2/M1 M3/M1 M4/M1 (Normalized to Input) y = relative load reduction; x = buffer width; a,b, and k – model coefficients • Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

7. Herbicide Properties 70 147

8. Antibiotic Properties

9. Relative Load Reduction - Atrazine • Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

10. Relative Load Reduction - Glyphosate • Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

11. Results Dissolved-Phase and Sediment Bound Transport Native Treatment Sediment Bound Dissolved Atrazine 120 100 80 60 40 20 • Atrazine and metolachlor were predominantly transported in the dissolved-phase (i.e., 95-98% was dissolved in the runoff water). • Glyphosate was transported in the dissolved-phase and as sediment-bound compound • Note that at -1 and 1 m ~60% was transported as sediment-bound. • At 4 and 8 m a large proportion of the sediment was deposited in the buffers and more glyphosate was in the dissolved-phase (~60%). 0 -1 1 4 8 Metolachlor 120 100 80 60 40 20 0 Glyphosate -1 1 4 8 120 100 80 60 40 20 0 • Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO -1 1 4 8 Distance from source (m)

12. Metolachlor 8:0 8:1 2:1 1:1 Drainage to Buffer Area Ratio Grass Buffer DesignAnticipated Field-Scale Results Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

13. Results Summary of Statistical Differences - Herbicides • All grass treatments significantly reduced transport of all 3 herbicides • Similar load reductions for dissolved-phase and sediment-bound transport • Atrazine, ↓57-68% ; Metolachlor, ↓66-72%; Glyphosate, ↓77-81% (8m data) • Atrazine and metolachlor transport • Buffer width: 4m = 8m; both > 1m • Species: • Atrazine – no significant differences among grasses • Metolachlor – Native > TF or Hedge+TF • Glyphosate transport • Buffer width: 8m > 4m > 1m • Species: no significant differences among grasses • Reduction in herbicide loads as a function of buffer width followed 1st-order exponential decay model for all herbicides • Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

14. Relative Load Reduction - Sulfamethazine Dissolved-phase transport only • Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

15. Relative Load Reduction - Tylosin Dissolved-phase transport only • Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

16. ResultsSummary of Statistical Differences - Antibiotics • Sulfamethazine • All grass treatments significantly reduced transport • Load reductions: 81-89% (8m data) • Buffer width: 4m = 8m > 1m • Species: no significant differences among grasses • Reduction in loads as a function of buffer width followed 1st-order exponential decay model • Tylosin and Enrofloxacin • Dissolved-phase transport trends were not well described by 1st-order exponential decay model • <0.2% of applied transported in the dissolved-phase • Mainly sediment-bound transport • Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

17. Results Mechanisms for Reducing Transport • Infiltration • Runoff volume reductions: • 43% for TF • 42% for Hedge+TF • 56% for Native • Sediment Trapping • Sediment load reduced by: • 80% for Native and Hedge+TF • 47% for TF • Enhanced rhizosphere degradation and sorption • Increased microbial activity in VBS soils increases atrazine degradation (Lin et al. 2003, 2004, 2008, 2011) • Increased VA sorption in VBS soils compared to row cropped soils indicated less contaminant mobility in VBS soils (Chu et al., 2010). • Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO

18. Summary and Conclusions • Effect of Grass Species • All grass treatments significantly reduced transport of herbicides and VAs • Load reductions in the range of 60-90% for 4-8 m of VBS • For tylosin and enrofloxacin, only the TF treatment reduced transport • Effect of Buffer Width • Reduction in loads as a function of buffer width followed 1st-order exponential decay model • Expected field-scale results (20:1): 15-40% reductions • VBS effective on high runoff potential soils • Buffer Design • Regression equations account for the contaminant, drainage-to-buffer area ratio, and grass species • Provide simple, practical design criteria for land management agencies • Potentially achieve desired reductions with less land taken out of production • C3 grasses can be an effective alternative to C4 species • Translating Missouri USDA-ARS Research and Technology into Practice A training session provided by USDA-ARS-CSWQRU, 10-11 October 2012, Columbia, MO