UPTAKE OF A HYDROLOGIC TRACER (BROMIDE) BY RYEGRASS FROM WELL AND POORLY-DRAINED SOILS

Ryegrass (Lolium perenne L.) accumulated an average 32% of applied bro mide (Br-) in aboveground biomass. Bromide uptake was greater on a wel l-drained soil (38%) than a poorly drained soil (27%). Uptake was also affected by an interaction between season and N fertility. Bromide co ncentration of ryegrass was affected by interactions between soil drai nage and season, and between soil drainage and N fertility. The magnit ude of uptake shows Br- to be quite biologically reactive in the soil root zone. The impact of interactions between common experimental vari ables on Br- uptake makes it difficult to select settings where Br- up take will be low. Consequently, the amount and pattern of uptake among common experimental variables greatly restricts the settings in which Br- is an appropriate hydrologic tracer.