Soil and Polymer Properties Affecting Water Retention by Superabsorbent Polymers under Drying Conditions
- J. Yu *a,
- J.G. Shia,
- P.F. Dangb,
- A.I. Mamedovc,
- I. Shainbergd and
- G.J. Levyd
- a Institute of Water Resources, Huhhot, Inner Mongolia, P.R. China. 010020
b Inner Mongolia Agricultural University Huhhot, P.R. of China. 010018
c USDA-ARS-EWERU, 1515 College Ave., Kansas State University, Manhattan, KS 66502
d Institute of Soil, Water and Environmental Sciences, Agriculture Research Organization (ARO), The Volcani Center, P.O. Box 6, Bet Dagan 50-250, Israel
Superabsorbent Polymers (SAPs) are capable of swelling and retain large amounts of water. Knowledge of the ability of SAPs to retain the absorbed water under evaporative conditions is less understood. We saturated four SAPs, seven soils from the semiarid areas in Northwest China (control treatments), and mixtures of 100 g of soil with 0.5 g of SAP, with tap water (electrical conductivity [EC] = 0.5 dS m−1, sodium adsorption ratio [SAR] = 2 [mmolc L−1] 0.5) for 15 min. The water-saturated SAPs, soils and soil-SAP mixtures were then placed in an oven at 60°C, and loss of water to evaporation from each treatment was measured every hour for 7 h. Water content of the soils at saturation ranged between 0.306 and 0.522 g g−1 of soil, while after drying it dropped to <0.08 g g−1 of soil. Water content of the SAPs ranged between 30 and 199 g g−1 of SAP at saturation, and decreased to 17 and 108 g g−1 of SAP after 7 h of drying. The soil-SAP mixtures absorbed between 78.59 and 47.94 g of water and retained between 34.51 and 12.75 g of water after 7 h of drying. Generally, evaporative water loss from soil-SAP mixtures was slower than for SAPs alone. When the SAP particle size was larger (3–4 mm) the opposite trend was noted. Furthermore, the 3 to 4 mm sized SAP differed from its <1.5 mm counter parts, that is, the water content retained by the soil-SAP (3–4 mm) mixture exceeded the sum of that retained by each component material alone. This suggests a synergy between this SAP and the soils with respect to the mixtures’ ability to retain water during the 7 h of drying. Our results suggest that when use of SAPs in cultivated soils to mitigate water stress is being considered, the characteristics of water loss from the soil-SAP mixture should be taken into account and not just the amount of water that the SAPs can absorb when mixed with the soils.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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