WATER AND CHEMICAL-TRANSPORT THROUGH LONG-TERM NO-TILL AND PLOWED SOILS

Flow in sell macropores has been implicated as a mechanism for accelerated movement of agrichemicals into groundwater under conservation tillage practices. Strontium bromide hexahydrate, atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5 triazine), and alachlor (2-chloro-2'-6'-diethyl-N-[methoxymethyl]-acetanilide) were surface applied to 18 undisturbed 0.3 by 0.3 by 0.3 m sail blocks collected from three Ohio sells subject to long-term no-till (NT) and moldboard plowing (MP). Two 30-mm rains were applied to the block surface, and leachate was collected from 64 cells at the bottom of each block Leachate volume, amount cf chemicals leached, and visible pare area on bottom surfaces were determined for each cell. Semivariograms of cell leachate volumes revealed that water flow in both NT and IMP soils is spatially uncorrelated at a scale of 30 to 300 mm. Principal component analysis at the cell level demonstrated that water flow in both NT and MP blacks followed preferential pathways. The NT blocks transmitted larger water volumes and chemical amounts than MP bloch; however, differences were rarely significant. Principal component analysis of transport in individual blocks suggested that the tillage differences resulted from a higher proportion of strongly preferential pathways in NT blocks. Discriminant analysis yielded significant separation in the soil hydraulic behavior as influenced by tillage and demonstrated the interaction in this behavior between soil type and tillage treatment. It has become clearer that rainfall timing and intensity following chemical application may overshadow tillage effects on water and chemical transport in soils.