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ARS Home » Pacific West Area » Kimberly, Idaho » Northwest Irrigation and Soils Research » Research » Publications at this Location » Publication #375230
Research Project: Improving Management Practices for Irrigated Western Cropping and Dairy Systems to Contribute to Sustainability and Improve Air Quality

Location: Northwest Irrigation and Soils Research

Title: Cross-linked polymers increase nutrient sorption in degraded soils

Author
item Lentz, Rodrick
item IPPOLITO, JAMES - Colorado State University

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/23/2020
Publication Date: 3/1/2021
Citation: Lentz, R.D., Ippolito, J. 2021. Cross-linked polymers increase nutrient sorption in degraded soils. Agronomy Journal. 113(2):1121-1135. https://doi.org/10.1002/agj2.20542.
DOI: https://doi.org/10.1002/agj2.20542

Interpretive Summary: A cost-effective means of increasing plant available water in degraded and marginal soils is needed to expand the agricultural land base and maximize soil productivity and resiliency in the face of climate change and a burgeoning world population. Cross-linked polymer hydrogels such as polyacrylamide co-polymer and K-polyacrylate, have been shown to generate long-term increases soil water availability, but their long-term effects on soil nutrient status are unknown, even though such knowledge is important for assessing economic feasibility at the farm-scale. This 9-year study showed that the hydrogels substantially alter the long-term chemistry of soil and associated drainage water, but effects differed greatly depending on hydrogel type and application rate. If properly managed, hydrogel-amended soils can increase nutrient availability to crops and reduce nitrate nutrient losses in drainage water. This information provides important guidance for hydrogel use, particularly at the farm scale.

Technical Abstract: Cross-linked polymer hydrogels, such as polyacrylamide co-polymer (XPAM) or polyacrylate (XPAA), can alter soil chemistry and crop nutrient uptake but the persistence of these effects has been little studied. This 9-y, irrigated, outdoor pot study evaluated a single, one-time addition of XPAM or XPAA at 0.25% or 0.5% dry wt. (5.6 or 11.2 Mg ha-1) in a degraded calcareous silt loam. Controls included an unamended degraded soil and an unamended, non-degraded soil (i.e. topsoil). Soils were hand-tilled and planted to crops each year. We measured nutrients in soil and leachate water each year, and in the first 5 y, crop yields and nutrient uptake. Both hydrogels increased average soil pH and electrical conductivity (EC), soil extractable K, Na, and TOC, and decreased soil extractable Mg relative to the control. Unlike XPAM, XPAA produced a greater increase in soil extractable K, increased extractable Fe, Zn, Mn, and Cu, increased Olsen P, and decreased total inorganic C. Neither hydrogel affected crop yields but XPAA increased K and Zn and decreased Mg and Na uptake in crops compared to controls. Relative to the control, both hydrogels decreased cumulative Ca, Mg, and S leaching mass losses and increased mean EC of leachate. Unlike XPAM, XPAA increased cumulative leaching mass losses of K, P, NO3-N, and NH4-N relative to the control. The hydrogels’ soil effects persisted for greater than or equal to 7 years and their effect differed as a function of the quantity of included counterions and the stability of the gel structure after soil placement.