RT Journal Article
SR Electronic
T1 A field study of macropore flow under saturated conditions using a bromide tracer
JF Journal of Soil and Water Conservation
FD Soil and Water Conservation Society
SP 376
OP 380
VO 46
IS 5
A1 J. D. Jabro
A1 E. G. Lotse
A1 K. E. Simmons
A1 D. E. Baker
YR 1991
UL http://www.jswconline.org/content/46/5/376.abstract
AB Nitrate-nitrogen (NO3-N) movement from agricultural land into surface water and groundwater is a serious environmental problem on soils derived from limestone in southeastern Pennsylvania. Pollution of groundwater with nitrates in this region is associated with high animal density, which leads to excessive manure-N application on field corn grown for grain and silage on dairy farms. Soil macropores or cracks are an important factor in determining the rate and depth of movement of water and solutes. This field investigation was conducted to characterize the movement of water and solutes in soils with dual pore systems using bromide as a tracer under saturated conditions. Infiltration rates and bromide transport were measured using double-ring infiltrometers on Duffield silt loam (fine-loamy, mixed, mesic Ultic Hapludalf) and Clarksburg silt loam (fine-loamy, mixed, mesic Typic Fragiudalf) in southeastern Pennsylvania. The lowest infiltration rate was 1.2 cm/hr and the highest was 33.5 cm/hr, with a mean of 11.2 cm/hr and coefficient of variation of 81%. The distribution of bromide tracer in the soil profiles was highly variable. A mean recovery of applied bromide tracer in the soil profiles was 50%. The mean value relates well with results for nitrate monitoring in soil profiles over the winter and early spring months, which indicated that about 50% of the NO3-N remaining within the soil profile in the fall was still present in the profile when the soils reached field capacity in the spring. The data provide strong evidence that the properties of limestone soils in southeastern Pennsylvania result in preferential movement of water and tracer through soil macropores. Because NO3-N has been shown to move similarly to bromide in soils, the results indicate that NO3-N contained in irrigation water or fertilizer solutions added to soils could result in preferential movement of NO3-N from the root zone to groundwater under saturated conditions. However, rainfall received during the year when the soil is at or near saturation can also be expected to provide substantial groundwater recharge without substantial leaching of nitrate in these soils.