Preparation of nutrient hydrogels with core-shell structure for seed germination and seedling growth in high temperature saline environment.

Drought and soil degradation are the key factors in desertification control. How to improve the utilization efficiency of water and fertilizer has always been the focus of research in desert areas. The conventional hydrogel-loaded fertilizer is not suitable because of the high salinity and large temperature difference in sandy land. Therefore we prepared a novel temperature/pH-responsive core-shell structured hydrogel and loaded urea in three ways: in situ polymerization, encapsulation, and immersion, and germination and seedling growth experiments on Artemisia absinthium and Cabbage (Brassica campestris L. ssp. chinensis Makino) seeds. The results showed that the immersion hydrogel SAP4 (PCP-g-PAA/P(DMAEMA-co-AMPS))/urea had the best repetitive swelling performance, achieving 163.89 % of the original water absorption performance after 16 repetitions and the highest nitrogen release of 151.37 mg at 40 days. For A. desertorum, the treatment group applying the in situ composite hydrogel SAP2 (PCP-g-PAA/P(DMAEMA-co-AMPS)/urea) had the highest germination rate of 70 %; for B. campestris, the treatment groups applying SAP2, the encapsulated hydrogel SAP3 (PCP-g-PAA/urea/P(DMAEMA-co-AMPS)) and SAP4 hydrogels had higher germination rates, with SAP3 having a 100 % germination rate. This phenomenon suggests that the three urea-loaded temperature/pH-responsive core-shell structured hydrogels we have prepared are very promising as an aid to seed germination and seedling growth in high temperature saline environment.