Superabsorbent Polyacrylamide Effects on Hydrophysical Soil Properties and Plant Biomass in a Sandy Loam soil

Abstract

There is a complicated relationship between land degradation, water efficiency, and crop yield in arid and semiarid regions. In the Semiarid Pampa region, Argentina, land use changes that affected fragile lands (high content of fine sands plus silt and low organic carbon) have decreased soil quality, thus endangering agricultural activities. The use of polyacrylamide (PAM) is an option for increasing productivity and protecting soil resources. However, there is scarce information about superabsorbent PAM on water storage linked to aggregate stability mechanisms in this fragile land. Hydrophysical variables and plant biomass were evaluated in a greenhouse pot experiment. Three factors were analyzed: 1) PAM rates (doses): D0 = 0%, D1 = 0.04%, and D2 = 0.08%; 2) vegetation presence (Festuca arundinacea ssp.): vegetation (+) and vegetation (–) and; 3) water regime: field capacity (FC) and half field capacity (FC/2). After 5 months, the incorporation of superabsorbent PAM had a strong effect on most hydrophysical variables. Storage variables (available water content and easily available water content) were improved mainly by increasing water retention at lower suctions (i.e. large pores). Dose increments regardless of the water regime led to higher plant biomass (P < .05). PAM incorporation enhanced abiotic mechanisms (swelling–shrinkage, cracks formation) and biotic mechanisms (root activity–direct, increment water retention–indirect) acting synergically to increase aggregate stability and water storage. Aggregate stability tests (fast wetting test–FW, slow wetting test–SW, and stirring aggregates after ethanol submersion–Stir) proved to be useful in discriminating stabilization mechanisms of soils, highlighting the effect of PAM incorporation on soil cohesion (Stir). Finally, superabsorbent PAM may contribute to maintain crop yields, leading to soil quality amelioration.