Nutrient Loss Through Tile Drainage Enhanced by Soil Cracks.

Shrink and swell soils often make cracks on the soil surface when they desiccate.  Cracks may become preferential pathways of water and nutrient.  We investigated whether cracks enhanced nutrient loss from Brookstone clay loam through tile drainage in Woodslee, Ontario, Canada.  Soil cracks were frequently pictured at approximately 1 m above the ground with a digital camera.  At the same time, volumetric water content of 0-0.2 m deep surface soil was measured with a vertically-inserted time domain reflectometry probe.  The pictures cracks were analyzed to determine the specific areas of cracks.  The water quality and quantity of surface runoff and tile drainage from experimental plots were automatically monitored.  A linear relationship between volumetric soil water content and the specific area of cracks was found.  The specific area of soil cracks increased as soil water content decreased with desiccation.  Another linear relationship between the specific area of cracks and surface runoff was found.  The amount of surface runoff water increased as the specific area of cracks decreased.  We did not have enough data for tile drainage to investigate a relationship with cracks.