Chemical irrigation is being used increasingly as a means of applying
agricultural chemicals, but the effects of different irrigation practi
ces on the movement and distribution of these chemicals in the soil ar
e not well understood. This paper reports the results of a field study
where bromide is applied as a tracer under both sprinkler and ponded
irrigation. The travel-depth bromide concentration curves under sprink
ler irrigation were smooth and unimodal, with very little variability
between soil cores. For ponded irrigation, however, the curves were bi
modal and showed much greater variability between cores. The writers a
ttribute the differences in shape and variability to the presence of p
referential flow in the ponded case. Results of this study have import
ant implications for ground-water pollution potential and monitoring o
f the vadose zone,