Atrazine Loss in Runoff from No-Tillage and Chisel-Tillage Systems on a Houston Black Clay Soil
1996
Pantone, D. J. | Potter, K. N. | Torbert, H. Allen | Morrison, J. E.
Herbicide concentration and mass load of runoff depends, to a large extent, on soil management. This study was conducted to determine how tillage impacts herbicide losses in runoff from a vertisol soil on the Blackland Prairie of Texas. Atrazine [6-chloro-N-ethyl-N′-(1-methylethyl)-1,3,5-triazine-2,4-diamine] was applied at a rate of 2 kg a.i. ha⁻¹ to a Houston Black clay soil (fine, montmorillonitic, thermic Udic Pellustert) in 1993 at the Blackland Research Center in Temple, TX. For 4 yr, the test area was under continuous management using a wide-bed system with a wheat (Triticum aestivum L.), corn (Zea mays L.), and grain sorghum [Sorghum bicolor (L.) Moench] rotation. Tillage treatments consisted of no-tillage or chisel-tillage. All experiments were repeated four times. A rainfall simulator with an intensity of 12.5 cm h⁻¹ was used to apply rainfall 24 h after the atrazine application. Sediment and runoff samples were collected during five time periods (from runoff initiation to 5, 5 to 10, 10 to 20, 20 to 30, and 30 to 40 min). No differences in atrazine concentrations were found among treatments in either the runoff water or sediment from any of the five time periods; however, crop residues prevented surface seal development and erosion resulting in reduced runoff and sediment losses. No-tillage treatments significantly reduced runoff and sediment yield, rather than the atrazine concentration of the runoff, resulting in a 42% decrease of the atrazine load in the runoff and a 77% decrease in atrazine associated with the sediment. As a percentage of the total amount applied, runoff accounted for <2% of the atrazine. Sediment-transported atrazine was much less important and represented <0.03% of the total amount applied. Approved for publication by the Texas Agricultural Experiment Station, Texas A&M University System.
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