Effects of Superabsorbent Polymers on the Hydraulic Parameters and Water Retention Properties of Soil

Shumei Ren,Peiling Yang,Renkuan Liao,Wenyong Wu

doi:10.1155/2016/5403976

Abstract

Superabsorbent polymers (SAPs) are widely applied in dryland agriculture. However, their functional property of repeated absorption and release of soil water exerts periodic effects on the hydraulic parameters and water-retention properties of soil, and as this property gradually diminishes with time, its effects tend to be unstable. During the 120-day continuous soil cultivation experiment described in this paper, horizontal soil column infiltration and high-speed centrifugation tests were conducted on SAP-treated soil to measure unsaturated diffusivityDand soil water characteristic curves. The experimental results suggest that the SAP increased the water retaining capacity of soil sections where the suction pressure was between 0 and 3,000 cm. The SAP significantly obstructed water diffusion in the soil in the early days of the experiment, but the effect gradually decreased in the later period. The average decrease in water diffusivity in the treatment groups fell from 76.6% at 0 days to 1.2% at 120 days. This research also provided parameters of time-varying functions that describe the unsaturated diffusivityDand unsaturated hydraulic conductivityKof soils under the effects of SAPs; in future research, these functions can be used to construct water movement models applicable to SAP-treated soil.

Highlights

The application of superabsorbent polymers (SAPs) for the purpose of enhancing soil water retention represents an important nonengineering water conservation technique for dryland farming
The water retention properties of soil are closely correlated with the pore size, while the water characteristic curve of a soil sample represents the relationship between its porosity and water content
An in-depth analysis of the SAP-treated soil in this study revealed that the SAP had the greatest effect on water retention in soil sections with suction pressure between 100 and 800 cm, because these areas exhibited the greatest increases in water content compared to the control group and other sections in the treatment groups

Summary

Introduction

The application of superabsorbent polymers (SAPs) for the purpose of enhancing soil water retention represents an important nonengineering water conservation technique for dryland farming. Applying SAPs to the soil is effective in improving rainwater use efficiency in dryland farming areas [8, 9], because SAPs can repeatedly absorb and retain rainwater entering the soil to reduce deep seepage losses and gradually release the water to the plants as the soil dries and the plants’ root pressure increases. This mechanism ensures a continuous water supply for plants during their growth periods [10, 11]

Methods

Results

Conclusion