Water retention properties of a sandy soil with superabsorbent polymers as affected by aging and water quality

Abstract

Hydraulic properties, specifically the water holding capacity of soils, play a key role in the ability of soils to sustain plant growth. Additions of hydrophilic polymers (superabsorbents) can improve the water holding capacity of sandy soils. This has led to practical applications of these materials particularly in arid regions and countries, where water is the limiting factor for plant production. The objectives of this study are to investigate how effective hydraulic properties of polymer-soil mixtures are affected by addition of absorbents in different concentrations. Novel aspects are the investigation of aging under repeated wetting-drying-cycles over an appreciable time in the field and a systematic investigation of the salt influence on the water uptake of polymers. We added the polymer Super AB, A-200 (Iran Polymer Institute), to dune sand in ratios of 0.3%, 0.6%, and 1% w/w. We found that the effective water retention characteristics of the soil-absorbent mixtures were improved with respect to plant-available water compared to the pure sand, and the improvement was related to the respective amount of absorbent in the mixture. The plant available water content (PAW) increased from 0.005 for the untreated sand to 0.06, 0.20, and 0.28 g g -1 , respectively, for the sand with the three polymer additions. Due to aging of the polymers, PAW decreased after 6 months of cyclic drying and wetting to about half of the value immediately after the initial treatment. We attribute this to the effect of salts. This is corroborated by the results from water uptake experiments by the pure polymers. Repeated cycles of water uptake showed that salts in the water greatly reduced the uptake capacity of the polymers after few cycles. The effect was strong for bivalent cations and less pronounced for monovalent cations.

Superabsorbent Polymer Properties and Concentration Effects on Water Retention under Drying Conditions

“…Our data (Fig. 3) further suggest that, based on the findings of Banedjschafie and Durner (2015), the higher water content in the soil-SAP mixtures compared with the soil alone combined with the linear decay of the drying curves for the soil-SAP mixtures, have a substantial contribution to plant available water over that provided by the soil alone.…”

“…The application of SAP increased soil water content at field capacity and at permanent wilting point, which may lead to a considerable increase in available water content in soils of different texture used under various crops' management (Karimi et al, 2009;Agaba et al, 2010;Shahid et al, 2012;Banedjschafie and Durner, 2015;Montesano et al, 2015). This increase in the content of plant available water can, under conditions of climate change, mitigate abiotic stress (plant water shortage, high temperature and salinity stress); it could thus enable longer intervals between consecutive irrigations, and improve plant growth rate and performance (El-Hady et al, 1981;Baker, 1991;Silberbush et al, 1993;Singh, 1998;Hüttermann et al, 1999;Viero et al, 2002;Han et al, 2005;Beniwal et al, 2010).…”

“…A few other studies also reported favorable effects of increasing SAP concentration (0-0.3%) on soil moisture and crop growth indices (Bai et al, 2010;Nazarli et al, 2010;Malekian et al, 2012). Recently, Banedjschafie and Durner (2015) clearly showed for a sandy medium that addition of 0.2, 0.6 or 1% SAP increased plant available water (determined as the difference in water content between field capacity and wilting point) from 0.3% in the control to 3.7, 12.2 or 17.7%, respectively.…”

Rice Husk Char/Poly-(Acrylic Acid-co-acrylamide) Superabsorbent Hydrogels: Preparation, Characterization, and Swelling Behaviors

“…Because of superior properties compared to traditional materials such as sponges, they are widely used in hygiene (Kosemund et al 2009), agriculture (Guo et al 2005;Liang et al 2009), drug delivery (Reddy et al 2011;Oun et al 2014), and water purification (Zheng et al 2010;Wang et al 2011). The research on the use of superabsorbents as water and fertilizer managing materials for the renewal desert environment (Banedjschafie and Durner 2015) and slow release fertilizers (Li et al2016;Yamamoto et al 2016) has attracted great attention, and encouraging results have been observed, as they can reduce irrigation water consumption, lower the death rate of plants, and increase plant growth rate (Parvathy et al 2014).…”

An investigation into the use of Australian native plants and designer metal-binding particles for remediation of metal-contaminated landscapes

“…However, the capacity of the polymer to retain water decreased progressively by about one-quarter over a 100-day experiment, presumably as the polymer sorbed Pb . Banedjschafie and Durner (2015) also revealed that the water holding capacity of cross-linked polymers in sand deceased by about half during a period of six months, which they attributed to the accumulation of salts. In addition, soil enzymatic activities such as urease (which catalyses the hydrolysis of urea to CO 2 and NH 3 ) were inhibited by the application of polymer (de Varennes et al, 2010) suggesting potential toxicity.…”