|Koehn, Anita - UNIVERSITY OF IDAHO|
Submitted to: American Society of Agricultural Engineers Meetings Papers
Publication Type: Abstract Only
Publication Acceptance Date: December 10, 2000
Publication Date: N/A
Technical Abstract: Water-soluble anionic polyacrylamide (PAM) is employed in furrow irrigation to control soil erosion & increase infiltration. We hypothesized that post-irrigation deep percolation & preferential-flow patterns for the PAM treatment would differ from that of the conventionally irrigated (CI) furrows. Portneuf silt loam plots 179 m long were planted to corn & irrigated using either conventional or PAM treatment. We added PAM to advancing irrigation furrow streams at 10 ppm. Inflow rates during furrow advance were 3X greater than that of conventionally irrigated furrows. Daily deep percolation volumes were collected after two irrigation events in 1998, & analyzed for nitrate-N & Cl concentrations. Two general patterns for daily percolation rate emerged. Under CI, percolation rate started high the first day after irrigation (1st peak), declined during the 2nd & 3rd days to a value about half of the 1st-peak value, then rose to a 2nd peak between 5 & 9 days after irrigation. PAM percolation rate started low on the 1st day after irrigation, peaked at about twice the initial rate on day two, declined on the 3rd day, then rose to a 2nd peak between 6 & 9 days after irrigation. Sample nitrate & chloride concentrations showed little relationship with sampler percolation rate, with one exception. During the first few days after irrigation, nitrate concentration in CI percolation water tended to increase as percolation rate decreased. Water rapidly moved downward from CI furrows after irrigation, & included bypass flow that diluted nitrate concentrations in deep percolation water. PAM treatment inhibited initial rapid downward movement of applied water, possibly by reducing preferential flow.