Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 8, 2000
Publication Date: N/A
Interpretive Summary: Controlling runoff and soil erosion are important for maintaining soil productivity and reducing off-site impairment due to sediment and nutrient enrichment. We compared the combined effects of surface residue and polyacrylamide (PAM) on runoff, soil loss and phosphorus loss from sprinkler irrigated soil in the laboratory. We wanted to determine if spreading straw on the soil surface would enhance the effectiveness of PAM applied with irrigation water. PAM reduced runoff, soil loss and phosphorus loss when applied to bare soil or straw-covered soil, but the beneficial effects of PAM did not last longer on straw-covered soil than bare soil. Straw applied at a rate similar to non-tilled conditions (70% surface cover) was more effective than applying 2 or 4 lb/a of PAM. Applying straw a rate similar to minimum tilled conditions (30% surface cover) was about as effective as applying either PAM rate. Reduced tillage systems increase surface residue and reduce production costs, whereas applying PAM costs $5 to 7 per pound. Therefore, producers should consider reduced tillage systems before applying PAM to control runoff and erosion under sprinkler irrigation.
Technical Abstract: Controlling runoff and soil erosion are important for maintaining soil productivity and reducing off-site impairment due to sediment and nutrient enrichment. Previous research has shown that crop residue and polyacrylamide (PAM) can reduce runoff and soil erosion. We compared the combined effects of surface residue and PAM on runoff, soil loss and phosphorus loss from sprinkler irrigated soil in the laboratory. We hypothesized that surface residue would enhance the effectiveness of sprinkler applied PAM by allowing PAM to stabilize the soil surface with less disturbance by water drops. Steel boxes (1.5 m long, l.2 m wide and 0.2 m deep) were filled with Roza loam (fine, smectitic, mesic xerertic Haplocambids) and irrigated at 80 mm h-1 for 15 min. Wheat straw was applied for two separate tests (70% and 30% straw cover). PAM was applied at 0, 2 or 4 kg ha-1 during the first irrigation, followed by two water-only irrigations. Applying PAM to straw-covered soil controlled runoff, erosion and phosphorus losses equally or better than using either PAM or straw alone. The 70% straw cover reduced cumulative runoff for the three irrigations 75 to 80% compared to 30 to 50% reduction with PAM alone. Polyacrylamide and 30% surface cover produced similar results, both reducing cumulative runoff 10 to 20%. Increasing surface residue through reduced tillage decreases production costs, but applying 2 kg PAM ha-1 increases production costs $20 to 30 ha-1. Therefore, reduced tillage management practices should be considered before PAM application for controlling runoff and soil erosion on sprinkler irrigated cropland.