Effects of several superabsorbent polymers on soil exchangeable cations and crop growth

Owing to their excellent water absorption and water retention properties, superabsorbent polymers have become an important technology for realizing agricultural water savings. To explore the exchange pathways of exchangeable cations in soil caused by different superabsorbent polymers and their effects on crop nutrient uptake and growth, three types of superabsorbent polymers, sodium acrylate, potassium acrylate and acrylamide–sodium acrylate, were used in this project to study the effects of different dosages on crop growth, root morphology and the distributions of Na+, K+, Ca2+ and Mg2+ in the root tips. The results were as follows: among all the treatments, the inhibition effect of the sodium acrylate superabsorbent polymer was the most obvious. Compared with CK, the biomass decreased by 70.3% (AN2), the root length and root surface area decreased by 62.7% and 61.1% respectively, plant K+ and Na+ increased by 18.5% and 2423% respectively, and Ca2+ and Mg2+ decreased by 27.6% and 18.7% respectively. Adsorption experiments with Ca2+ and Mg2+ further proved that the superabsorbent polymers adsorbed more than 95% of the Ca2+ and Mg2+ in the soil while releasing Na+ and K+ into the soil after swelling.