Laserfiche WebLink
Fate and Efficacy of Polyacrylamide Applied in Furrow Irrigation: Full-Advance and Continuous Tr... <br />Page 12 of 16 <br />Relative to the total Initial-10 PAM applied, cumulative PAM losses from Initial-10 furrows would have been 1 to 2% <br />(Irr. 1) or 5% (Irr. 2, 4, 5, 6) had PAM application been shut off at furrow advance (Fi~• g) .However, because PAM <br />application in Initial-10 furrows was permitted to continue for 75 to 120 min after advance, cumulative PAM mass <br />losses in runoff from Initial-10 furrows were 32% (Irr. 1) and 33% (Irr. 2, 4, 5, 6) of the total applied (data not <br />shown). By comparison, cumulative PAM losses from the ends of Cont-1 furrows averaged 15% (10 g) of the total <br />PAM a.i. applied to Cont-1 fiurows. <br />... <br />•Y !•M VL. fW wo ~ !y <br />•A ............................:::. •, <br />~ <br />lA 1 <br /> ' <br /> <br />° •° <br />1 mt <br /> <br />3 ~A v.w.~rw.~ <br />1 <br />u b <br /> <br />9 i9 1 <br />1 <br />10 j <br /> 1 ~•WY10, N.1 f Cf <br />1•I <br />OA 1 <br />0 <br />0 ! • • • 10 1! N <br />1#•14»IMmn! <br />View larger version (26K): <br />[in this windowl <br />[in a new windowl <br />Fig. 8. Cumulative polyacrylamide (PAM) loss from the end of Initial-10 <br />furrows, Irrigation 1, including cumulative PAM loss prior to and after <br />PAM shutoff (vertical columns). <br />Cumulative PAM a.i. losses increased as the irrigation season progressed. Zero PAM losses from the bottom and end <br />positions of the tail ditch occurred in Irrigations 1 and 2. In Irrigation 4, 4.2 g PAM was lost from the bottom, and 0.2 <br />g was lost from the end of the tail ditch. By Irrigation 6, a total of 22 g PAM was lost at the tail-ditch bottom and 9 g <br />at the tail-ditch end. Thus, season-long cumulative PAM losses at the tail-ditch and could have been nearly eliminated <br />if we had not treated the last two irrigations. <br />Polyacrylamide Sinks <br />The total PAM applied per irrigation averaged 61 g a.i. for Cont-1 furrows and 155 g a.i. for Initial-10 furrows, where <br />polymer application was allowed to continue for 75 to 120 min after runoff began. Of the tota1216 g PAM a.i. <br />applied, 51 g adhered to soil in Cont-1 furrows and 102 g adsorbed to soil in Initial-10 furrows. Thus, cumulative <br />PAM losses from the end of all treated furrows averaged 63 g a.i. per irrigation (28% of the total PAM a.i. applied). <br />Of this, 53 g was adsorbed to sediment present in the collection- and tail-ditch stream and removed from solution. <br />Hence, an average 10 g dissolved PAM a.i. passed into the tail ditch in each irrigation. Of this 10-g amount, 2.6 g <br />PAM a.i. (1% of the total applied) passed down the tail-water ditch and exited the farm. <br />/ CONCLUSIONS <br />This study compared effects of two PAM applications, Initial-10 vs. Cont-1, on <br />furrow irrigation-induced erosion and infiltration, and determined the fate of <br />applied PAM in furrow streams and downstream surface drains. Initial-10 more <br />effectively controlled furrow erosion overall, although Cont-1 did equally well <br />during late-season irrigations when erosion measured in untreated furrows was <br />lower. Cont-1 increased net infiltration above that for control or Initial-10 furrows <br />during the late-se son irrigations. <br />~ TOP <br />~ ABSTRACT <br />~ INTRODUCTION <br />~ MATERIALS AND METHODS <br />~ NOTES <br />~ RESULTS AND DISCUSSION <br />• CONCLUSIONS <br />~ REFERENCES <br />http://jeq.scijournals.org/cgi/contentlfulU31/2/661 9/21/2006 <br />