The effects of two new types of composite hydrogels on soil properties and tobacco growth

To improve the soil environment for tobacco cultivation and promote tobacco growth, polyvinyl alcohol-acrylic acid-biochar composite hydrogels (HB) and polyvinyl alcohol-acrylic acid-molecular sieve composite hydrogels (HM) were prepared through cross-linking polymerization reactions. The successful preparation of the hydrogels was confirmed using Fourier infrared spectrum (FTIR), Scanning electron microscope (SEM), and alpha ray spectrometer (EDS). The equilibrium swelling degrees of HB and HM were 141.07 and 157.78 g·g −1 , with degradation rates of 34.77% and 43.54% after 120 d of burial in soil, respectively. Soil leaching tests revealed that both HB and HM have excellent water retention and fertilizer retention properties, performing better than commercially available hydrogels (HS). Smoking seedling pot culture experiments showed that the addition of HB and HM hydrogels significantly improved the physical and chemical properties of the soil and microbial diversity. The total root length, total root surface area, and root volume of tobacco plants treated with HM were increased by 58.50%, 74.85%, and 45.94%, respectively. Biomass and leaf photosynthesis were significantly enhanced ( P < 0.001). The total amounts of HB and HM metabolites increased by 31.52% and 48.64%, respectively. This study provides a basis for the application of HB and HM in tobacco and other crops.