Temperature limitations in the use of hydrogels on leptosols in a semi-arid region of Brazil

Due to their high-water retention capacity, hydrogels are considered promising soil conditioners to improve soil plant available water content in semi-arid environments; however, little is known about how soil temperature affects the functionality of hydrogels. In this study, the effect of soil temperature on physical attributes of soil amended with a Acrylamide-co-Potassium Acrylate hydrogel was evaluated. A laboratory experiment was installed in a scheme (4 × 4) x 4 - four soil temperatures (30, 45, 65 and 105 °C), four exposure times (40, 70, 100, and 130 days) with four repetitions. The test soil was a Leptsol with sandy loam texture and of the hydrogel was applied at a dose of 0.1% w w−1. Soil moisture at field capacity (θFC) and permanent wilting point (θWP), plant available water (AW), bulk density (BD), and soil porosity were evaluated. The resulting data was subjected to two-way analysis of variance. The hydrogel increased the θFC of the soil, from 0.14 to 0.19 m3 m−3 at 45 °C and 56 days. At 40 days, a minimum θWP (0.05 m3 m−3) was observed at 92 °C. In general, θFC increased, while the θWP decreased, providing improved soil water storage. Plant available water was up to three times higher in soil with hydrogel across a temperature range of 30–105 °C. In all treatments irrespective of temperature and exposure time, the soil BD and porosity were improved in comparison to the un-amended control. This constitutes an advantage in the use of the hydrogel as a soil conditioner. Even with the interaction of abiotic factors acting on the hydrogel, there are beneficial effects on the water storage capacity, soil BD, and soil porosity.