Spatial Distribution of Enhanced Atrazine Degradation across Northeastern Colorado Cropping Systems
- Dale Shaner *a,
- Mary Strombergerb,
- Raj Khoslabc,
- Alan Helmd,
- Bruce Bosleye and
- Neil Hansenb
- a USDA–ARS, Water Management Research Unit, 2150 Centre Ave., Bldg. D Ste. 320, Fort Collins, CO 80526-8119
b Dep. of Soil and Crop Science, Colorado State Univ., Fort Collins, CO 80523-1170
c Precision Agric. Res. Chair, King Saud Univ., Riyadh, Saudi Arabia
d Colorado State Univ. Extension, 27 E. Denver, Holyoke, CO 80734-032815
e Colorado State Univ. Extension, 508 South 10th Ave., Ste. 1, Sterling, CO 80751-3408. Assigned to Associate Editor Jose-Julio Ortega-Calvo.
Reports of enhanced atrazine degradation and reduced residual weed control have increased in recent years, sparking interest in identifying factors contributing to enhanced atrazine degradation. The objectives of this study were to (i) assess the spatial distribution of enhanced atrazine degradation in 45 commercial farm fields in northeastern Colorado (Kit Carson, Larimer, Logan, Morgan, Phillips, and Yuma counties) where selected cultural management practices and soil bio-chemo-physical properties were quantified; (ii) utilize Classification and Regression Tree (CART) Analysis to identify cultural management practices and (or) soil bio-chemo-physical attributes that are associated with enhanced atrazine degradation; and (iii) translate our CART Analysis into a model that predicts relative atrazine degradation rate (rapid, moderate, or slow) as a function of known management practices and (or) soil properties. Enhanced atrazine degradation was widespread within a 300-km radius across northeastern Colorado, with approximately 44% of the fields demonstrating rapid atrazine degradation activity (laboratory-based dissipation time half-life [DT50] < 3 d). The most rapid degradation rates occurred in fields that received the most frequent atrazine applications. Classification and Regression Tree Analysis resulted in a prediction model that correctly classified soils with rapid atrazine DT50 80% of the time and soils with slow degradation (DT50 > 8 d) 62.5% of the time. Significant factors were recent atrazine use history, soil pH, and organic matter content. The presence/absence of atzC polymerase chain reaction (PCR) product was not a significant predictor variable for atrazine DT50 In conclusion, enhanced atrazine degradation is widespread in northeastern Colorado. If producers know their atrazine use history, soil pH, and OM content, they should be able to identify fields exhibiting enhanced atrazine degradation using our CART Model.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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