| heal.abstract |
Macropore flow has received increased attention in the recent years due to its importance on solute flow through the vadose zone and consequent contamination of groundwater. The effects of man-made macropores resulting from cultivation of turfgrass sites on the mobility of tracer dye (FD&C Blue Dye #1) were studied in free draining greenhouse lysimeters (300 mm I.D. by 463 mm deep) sodded with Agrostis stolonifera Huds. ssp palustris 'Providence'. Treatments included two soil profiles (305 mm of root zone sand on top of 50 mm coarse sand and 100 mm gravel), simulating a US Golf Association style putting green, and an Arkport sandy loam (Psamentic Hapludalfs coarse loamy mixed), three cultivation practices (shallow hollow tines, 80 mm deep and 19 mm I.D.; deep drill, 220 mm deep and 19 mm I.D.; and high pressure water injection) and two soil moisture regimes (100% and 50% of field capacity). Dye was applied uniformly with a peristaltic pump that delivered water under pressure through a full cone pesticide nozzle. The lysimeters were excavated and the flow pattern of the dye was traced with transparent sheets in various depths. It was observed that in sand at 50% field capacity (FC), dye moved through the aeration holes, even though, the aeration cavities had collapsed at the time of the application. This preferential flow resulted by the hydrophobicity of the thatch layer, which channelled water and dye towards the aeration holes. Preferential flow was also pronounced in the absence of aeration holes. In the sandy profiles that were at 100% field capacity, water and dye movement was more uniform compared to the drier ones. In the sand-50% FC the fastest dye movement was observed in deep drill treatment while in the sand-100% FC the differences between aeration treatments were minor. In sandy loam soil deep tine cultivation resulted in fast movement when the soil was at 100% FC. In contrast, hollow tine cultivation provided reduced dye movement similar to that of the control, while water injection resulted in moderate dye movement. In the sandy loam soil-50% FC all treatments provided fast movement of the dye that had preferential characteristics even in the non-aerated profiles. |
en |