Hydrogel synthesis based on lignin/sodium alginate and application in agriculture.

A new green hydrogel has been synthesized by crosslinking lignosulfonate (L), sodium alginate (SA) and konjaku flour (KJ). We have optimized the ratio of the three synthesized polymers using an orthogonal design of experiments and characterized this hydrogel using SEM, BET and FTIR spectra. We have added the hydrogel into soil and investigated its degradability in soil and its influence on chemical and physical properties of soil, such as maximum water holding capacity, saturated hydraulic conductivity, water retention curve and nutrient retention and evaluated its performance when applied in drought stress tests on tobacco plants. The results show that the maximum water absorption of optimized L/KJ/SA is 41.23 g/g. Adding the L/KJ/SA hydrogel to soil reduces saturated hydraulic conductivity, increases available water capacity of soil and reduces leaching of soil nutrient. The L/KJ/SA hydrogel can improve the photosynthetic capability of tobacco plants under drought stress and the levels of osmotic regulators such as proline and reducing sugar, and could prolong the growth time of tobacco plants up to 14 days, which significantly increases its mass harvest. The L/KJ/SA hydrogel also has good degradability, which can degrade 20% when buried in soil for 120 days.