Approach

A field study was initiated in 1998 near Kimberly, ID on Portneuf silt loam (coarse silty mixed superactive mesic durinodic Xeric Haplocalcids).  The study compared erosion from furrows that were a) sprayed with 1.3 mm (Figure 1), b) drip-wetted with 12 mm of water (Figure 2) and c) dry (Figure 3).  The study was repeated three consecutive days in 1998 on different plots each day in a single field recently taken out of sod (field #1).  In 1999 the study was repeated on field #1 and on two additional fields, one fallowed for several years (field #2), and immediately following dry bean harvest (field #3).  Slopes were 1 - 1.5%.  Inflow, runoff, and sediment content were monitored intensively over the course of 6 hours.  To focus results on the detachment and transport phase, furrows were 27 meters in length.  The most common inflow rate used was 30 l/min.  Inflow was varied in some studies to examine possible interactions.  Aggregate fractions and aggregate stability of each site were characterized, as were organic carbon, antecedent water content (Table 1, see below) and surface and water temperatures at the time of irrigation.  Sediment concentrations of outflow were integrated from periodic samplings to estimate sediment loss in runoff from each event.