Movement of Diuron and Hexazinone in Clay Soil and Infiltrated Pond Water

Abstract

ABSTRACTresult in runoff of residues so improved incorporation of pre-emergence herbicides into the soil is recomPre-emergence herbicide residues were detected in domestic wells mended to reduce concentrations in runoff water. fornia's ground water (Troiano et al., 2000). Pre-emeragricultural field where the soil was a cracking clay to infiltration of gence herbicide residues were detected in seven wells residues in water captured by an adjacent holding pond. Diuron and sampled within a 1554-ha area located near the town hexazinone were applied in December to a 3-yr-old alfalfa (Medicago of Tracy, CA: atrazine was detected in five wells at 0.16 sativa L.) crop. Water content of soil taken after major rainfall but to 2.8 g L Ϫ1, diuron in one well at 0.06 g L Ϫ1, hexazibefore irrigation at 106 d after application was elevated at the lowest none in three wells at 0.051 to 0.11 g L Ϫ1 , and simazine depth sampled centered at 953 mm, indicating water was available (6-chloro-N,NЈ-diethyl-1,3,5-triazine-2,4-diamine) in one for percolation. Herbicide residues (reporting limit 8 g kg Ϫ1 ) were well at 0.098 g L Ϫ1.Tracy is centrally located on the confined above the 152 mm soil depth, even after subsequent applicawestern side of the Central Valley of California (Fig. 1). tion of two border-check surface irrigations. The pattern of distribu-The predominant cropping pattern was a rotation of tion and concentration of residues in the soil were similar to results obtained from the LEACHM model, suggesting that macropore flow alfalfa with corn (Zea mays L.) and bean (Phaseolus was limited to a shallow depth of soil. Herbicide residues were meavulgaris L.). The residues were related to agricultural sured in runoff water at the first irrigation at 20 g L Ϫ1 for diuron applications, especially since the only reported pesti- ment of atrazine in cracking-clay soils in another area of California had been investigated (Graham et al., 1992). That study indicated potential movement of herbicides M ovement of pesticide residues from agricultural into cracks with some residues detected below the plow applications to ground water has been well doculayer, but movement to shallow ground water was not mented (Hallberg, 1989). In California, the approach to confirmed. regulation of pesticides detected in ground water is to Another potential pathway observed during the surallow continued use if management practices can be vey was water-holding ponds located within or near identified that mitigate the threat of contamination. This the cropped fields. The ponds collected runoff water course of action balances economic considerations with generated from rainfall or irrigation events. Through environmental protection. The effectiveness of this apinterviews, the ground water in this area was determined proach relies on elucidating the pathways for movement to be shallow at around 4500 mm. Since the ponds were of residues to ground water with concomitant developbetween 2400 and 3000 mm deep, excavation of the ment of farm management practices that...

Automation and evaluation of three pesticide fate models for a national analysis of leaching risk in Canada

“…The computer used in this study contained dual 3.06 gigahertz Intel ® XEON™ central processing units and 2 gigabytes of DDR-SDRAM. Miao et al 2004) LEACHP (Roy et al 2001;Pritchard et al 2005;Sarmah et al 2005) MACRO (Larsbo et al 2005;Lindahl et al 2005;Reichenberger 2005;Strömqvist and Jarvis 2005 ticide fate models PRZM, LEACHP, and MACRO report the amount of pesticide leached at 1-m depth which, for our purposes, is considered to be the leaching potential for movement of pesticides into ground water.…”

Soil and water management: opportunities to mitigate nutrient losses to surface waters in the Northern Great Plains

“…The chemistry of holding ponds can vary seasonally as a result of microbial processing and chemical precipitation and therefore the agronomic benefits of this nutrient source depend on the timing of its use for irrigation (Dickey and Vanderholm 1977). There are very clear benefits to managing feedlot runoff, but environmental trade-offs do merit mention, including risk of contamination of surface water and groundwater if containment is insufficient (Prichard et al 2005).…”

Pesticide and Nitrate Trends in Domestic Wells where Pesticide Use Is Regulated in Fresno and Tulare Counties, California

“…Drywells, in particular, were unique to the areas with hardpan soils because they provided drainage and relief from flooding for newly planted citrus crops through channeling of runoff water to boreholes that were drilled through the surface layers of the soil and backfilled with gravel or rock (DeMartinis and Royce, 1990). These sensitive sites provided a direct route for water to enter the subsurface soil and accelerate groundwater recharge (Braun and Hawkins, 1991; Prichard et al, 2005). Data for DGW were obtained from monitoring wells maintained by the California Department of Water Resources.…”