Field evaluation and model calibration for agricultural pesticide transport to groundwater - phase II
Abstract
Certain soil physical and chemical property data are needed to predict transport of agricultural chemicals (pesticides, herbicides, etc.) to groundwater. The objective of this investigation was to evaluate the soil variability of selected soil physical and chemical properties in a field used to study atrazine and bromide leaching. The site was divided into three areas due to differences in surface texture. Area I had a surface texture of sand, Area II sandy loam, and Area III loam. Soil physical properties were measured on 455 undisturbed soil samples taken systematically at 91 locations at five selected depths (15 to 20 cm depth increments to a depth of 85 cm) throughout the field. Additional samples were taken for measurement of organic matter content and pH. Organic matter content values of the three soil areas were similar throughout the soil profile. However, there was an additional peak (besides that at the soil surface) of organic matter content at the 100 cm depth in all areas. This was probably due to buried plant materials. Salt pH of Area I was higher down to the 65 cm depth compared to Areas II and III. Soil bulk density values throughout the soil profile were similar for the three soil areas. Interestingly, bulk density decreased with increasing soil depth which was attributed to the coarser texture of soil particles with increasing depth. Below the third depth, over 80 percent of the samples had 90 percent or more sand of which at least 85 percent was very coarse (1.0 to 2.0 mm). Saturated hydraulic conductivity values 7 of the three areas were similar for the shallow depths. At the 55 cm depth however, Area I had higher saturated hydraulic conductivity values than Areas II and III. The soil water characteristics of the three areas were similar for the five measured depths.