MACROPOROSITY AND ITS RELATION TO SATURATED HYDRAULIC CONDUCTIVITY UNDER DIFFERENT TILLAGE PRACTICES

To aid in predicting ranges of saturated hydraulic conductivity (Ksat), macropore distribution in situ was characterized by exposing selected horizontal planes and tracing macropores on clear polyethylene sheets. Below the maximum tillage depth, macropores were present at all locations, but tillage disrupted continuity of pores from the surface. No-till had macropores throughout the upper 70 cm with continuity observed in the 0- to 35-cm range. Numbers of pores (>0.4-mm diam.) per m2 ranged from 100 to >3000, representing 0.1 to 2% of the total area. When present, horizontal crack length ranged from 1.7 to 19.3 m m-2. Measured Ksat on undisturbed detached cores ranged from 1.1 to 180 μm s-1 with CVs ranging from 44 to 197%. The Ksat could be estimated within a range (out of eight classes) from descriptions of biopore area, cracks, soil structure, and soil texture. -from Authors