Multiple polyacrylamide applications for controlling sprinkler irrigation runoff and erosion

Runoff under sprinkler irrigation systems causes soil erosion and reduces w ater infiltration uniformity. Previou studies have shown that applying poly acrylamide (PMA) with irrigation water can reduce runoff and soil loss. We hypothesized that applying PAM with three consecutive irrigations would mor e effectively control runoff and erosion than applying the same total amoun t of PAM with a single irrigation. This study was conduced in the laborator y with a Rad silt loam (coarse silty, mixed, superactive mesic Durinodic Xe ric Haplocambid) at 6.5% slope. Water was applied at 80 mm h(-1) (3.2 in. h (-1)) for 10 min [13 mm (0.5 in.) application depth] for four irrigations. PAM was applied at 3 kg ha(-1) (2.7 lb a(-1)) with irrigation water during the initial irrigation (single) or at 1 kg ha(-1) (0.9 lb a(-1)) during the first three irrigations (multiple). Both multiple and single PAM treatment s caused significantly less runoff than the control for all four irrigation s. However, the multiple PAM treatment reduced runoff approximately 30% mor e than the single application during the last two irrigations. Applying PAM at 3 kg ha-1 (2.7 lb a-1) with one irrigation reduced cumulative soil loss by 60% compared to the control. Applying PAM at the same rate in three con secutive irrigations reduced cumulative soil loss by 80%. Both single and m ultiple PAM applications reduced runoff and soil loss, but multiple applica tions more effectively controlled Runoff longer than a single application.