SOIL MACROPORES AND SURFACE WATER QUALITY IN TILE DRAIN SYSTEMS

This study explored the timing and extent of macropore flow to tile drains and potential effects on surface water quality. The study site in Clinton County, northeastern New York, is in the Adjidaumo soil series under intensive dairy management with periodic applications of dairy manure. Smoke experiments demonstrated extensive continuity between the tile and soil surface. Surface application of a brilliant blue dye-tracer suggested that both fissures and earthworm channels were important in these “moderate” shrink-swell soils containing montmorillinite. Infiltration rates were bimodal depending on the presence or absence of surface macropore channels. Consistent differences were observed between B horizon soil matrix and macropore surfaces, which tended towards the chemical signature of overlying Ap horizons. Manure applications in small plots above a tile demonstrated flow to tiles within 20 minutes with substantially higher total phosphorus concentrations. Tile effluent concentrations of total phosphorus increased by as much as two orders of magnitude within one day after manure applications to the field and then fell rapidly to near baseline levels within 4-5 days.

High phosphorus concentrations in applied manure may be carried rapidly downward along macropore channels and have little chance for retention on surface adsorption sites in the soil matrix. Manure application on some tile-drained soils, particularly those prone to forming extensive macropore drainage networks, may exacerbate surface water pollution.

The Miner Applied Environmental Science Program is an intensive program for senior environmental science majors at SUNY Plattsburgh in which students live in residence at our off campus field facility at the Miner Agricultural Research Institute. Day long, flexible-format field courses involve students in hands-on courses incorporating instances of inquiry-based learning and original research. This investigation was designed and implemented by the soil science class.