The effect of polyacrylamide on runoff, erosion, and cotton yield from fields irrigated with moving sprinkler systems

Irrigation with self-propelled moving sprinkler irrigation system (MSIS) enhances seal formation at the soil surface and results in large amounts of runoff and erosion which are aggravated by the MSIS high water application rate and reflected in lower yields. The effect of polyacrylamide (PAM) application (at the equivalent rate of 20 kg ha^-1), prior to the irrigation season, on runoff and erosion from bare soil and soil covered with a crop, as well as on cotton yield was studied in a clay loam vertisol (Typic Chromoxert) and a silt loam loess (Calcic Haploxeralf). A center pivot and a lateral MSIS were used in the vertisol and loess, respectively. Vegetative growth of cotton plants in the vertisol was inversely related to water application intensity, which in turn affects runoff. PAM significantly reduced runoff in both the bare and crop-covered soils. The runoff level from the PAM treatments was 50-70% of that of the control. PAM also reduced erosion especially in the vertisol soil. However, the amount of eroded material carried by a unit runoff was similar in both treatments for both soils, indicating that PAM influences erosion by reducing runoff levels. A trend whereby PAM increased yield of cotton (Gossypium hirsutum L., cv. Pima S5) compared with the control was observed. Our results suggest that, under irrigation with a MSIS, reducing runoff is essential for obtaining higher yields. PAM is suggested as an effective tool to attain this target.