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Long-term water retention increases in degraded soils amended with cross-linked polyacrylamide

Lentz, R.D. (2020) Long-term water retention increases in degraded soils amended with cross-linked polyacrylamide. Agronomy Journal. 112(4):2569-2580. 19 March 2020.

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Abstract

Polymer hydrogels, cross-linked polyacrylamide co-polymer (XPAM) and K-polyacrylate (XPAA), increase soil water availability under drought, but their long-term effects are unknown even though such knowledge is important for assessing economic feasibility at the farm-scale. This 9-yr, outdoor study amended an irrigated, calcareous silt loam with a one-time, 0.25% or 0.5% dry wt. (5.6 or 11.2 Mg/ha) application of either XPAM or XPAA; and included an untreated control and untreated, uneroded topsoil. Soil water retention and plant available water (PAW, g H2O per g dry soil) were measured in soil samples collected in spring for 7 of the 9 years. Across all years, the 2% XPAM produced the greatest PAW (0.318) and the PAW of other treatments followed in the order: 0.5% XPAM > 0.25% XPAM > Topsoil > 0.25% XPAA = 0.5% XPAA = control (0.224). In all years, the 0.25% XPAM and 0.5% XPAM treatments increased soil PAW relative to the control, i.e. their PAW ratios exceeded unity. Topsoil PAW exceeded that of the control in 6 of the 7 years measured. The PAW of 0.25% XPAM and 0.5% XPAM peaked in year one after application and declined linearly with time (P<0.03), at -0.0036 /yr and -0.0044/yr, respectively. Hence, the half-life of the XPAM-related water-retention benefit is 10 to 16 years. In this study, soil water-retention benefits from XPAM amendments exceeded projections proposed by the industry (5 years in soil) and suggests that the cost-benefit of farm-scale XPAM applications might be more favorable than previously anticipated.

Item Type: Article
NWISRL Publication Number: 1675
Subjects: Polyacrylamide (PAM) > Cross-linked (hydrogel) PAM
Soil > Chemistry
Soil > Soil quality
Soil
Depositing User: Michelle Wayment
Date Deposited: 21 Jul 2020 22:09
Last Modified: 21 Jul 2020 22:09
Item ID: 1716
URI: https://eprints.nwisrl.ars.usda.gov/id/eprint/1716

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