Macropore effects on pesticides transport to groundwater
Abstract
The objective of this investigation was to evaluate the leaching and degradation characteristics of atrazine and bromide in a field of alluvial soils under irrigated, no-till management. The experimental site was 0.1 ha in size. The soils were Sarpy (mixed, mesic Typic Udipsamments) with the surface texture varying from silt loam to loamy sand. Atrazine was applied at 2.2 kg/ha after sorghum (Sorghum bicolor) was planted. Bromide was applied at 115 kg/ha five days later. Soil cores were extracted to a depth of 150 cm which were segmented into 7.5 cm increments and were analyzed for each of the chemicals separately. The dates for sampling were one week, one month, two months, three months, and four months after application of the chemicals. As a result 1134 and 3542 soil samples were extracted for atrazine and bromide analysis, respectively. Atrazine was detected within the 15 to 22.5 cm depth increment one week after application. These data suggest that some of the atrazine can move to depth of 20 cm after one week which is probably due to the presence of macropores (1-5 mm diameter holes) open to the soil surface which were present in this field under no-till management. Atrazine was detected at very low concentrations at two and four months after application. Although extreme variability in atrazine concentrations occurred, the variations were not explained totally by differences in soil texture. The data in this study indicate some potential, although small, for atrazine contamination of groundwater.