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Incidental movement to drainage tile following application of liquid waste was monitored to identify driving factors and mitigation practices. In silt loam, liquid swine manure (LSM) was either topdressed (TD) or injected (INJ) into standing corn at rates ranging from 0 to 94 m3 ha-1 (2000-02). Concentrations of NH4-N and dissolved reactive P (DRP) were good indicators of tile water contamination, which occurred immediately after injection of 75 and 94 m3 LSM ha-1 (75-cm centers). Following injection of 56 m3 ha-1 or less, tile drainage water was clear and NH4 and DRP concentrations were much lower, even when tile were flowing prior to application. With TD of 37 or 56 m3 ha-1, nutrients did not move to tile at time of application, but NH4-N and DRP concentrations increased with rains that fell within 3 d after application. Following application of 112 m3 biosolids ha-1 injected on 38-cm centers or dropped behind rolling tines on the (drier) silt loam after wheat (2004), there was no incidental movement to tile. On loam and sandy loams following injection of 140 m3 biosolids ha-1, no by-pass flow occurred irregardless of injector spacing (ranged 46-76 cm) or antecedent soil water content. Lumbricus terrestris burrows provided the main transfer mechanism in susceptible fields and application rate was a critical driver. Best Management Practices to minimize risk of contamination include choosing at least one of:

1. Apply at rates < 40 m3 ha-1, or
2. Pre-till within 7 days of application, or 3. Apply when:
No tile flow
Tiles blocked
Tiles discharge to holding pond, or
4. Observe tile outflow, or
5. Observe following application at the planned rate over a smaller but representative test area of tile

Stop if discoloration observed.