Bromide Transport under Sprinkler and Ponded Irrigation

Chemical irrigation is being used increasingly as a means of applying agricultural chemicals, but the effects of different irrigation practices on the movement and distribution of these chemicals in the soil are 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 sprinkler irrigation were smooth and unimodal, with very little varriability between soil cores. For ponded irrigation, however, the curves were bimodal and showed much greater variability between cores. The writers attribute the differences in shape and variability to the presence of preferential flow in the ponded case. Results of this study have important implications for ground-water pollution potential and monitoring of the vadose zone.