Synthesis of a pH-responsive nano-cellulose/sodium alginate/MOFs hydrogel and its application in the regulation of water and N-fertilizer.

In order to circumvent the water eutrophication caused by nitrogen loss in agriculture, slow-release and high-water containing fertilizers have captured much attention. Considering the unstable release of traditional slow-released fertilizers, novel strategies need to be designed to meet the steady release of fertilizers. Herein, by integrating cellulose-based hydrogel with MIL-100(Fe), a pH-sensitive Cellulose/MOFs hydrogel (CAM) with a high surface area (45.25 m2/g) was devised. The volume changes and the water adsorption of the hydrogels were uncovered from pH 3 to pH 11, where the highest water adsorption (100 g/g) was achieved at pH 11. Besides, a pH-sensitive urea slow release fertilizer (U-CAM) was also designed. The urea release of the U-CAM at pH 11 was much slower than that of the U-CAM at pH 3, which indicated its potential application in arid regions. In parallel with a favorable water-holding capacity, the totally loss of the soil moisture loaded with U-CAM was slowed down by 18 days as compared with the pure soil. The positive effect of the U-CAM on the growth of wheat was indexed with the germination rate, number of tillers, photosynthetic rate and chlorophyll content of the crop, which verified their further application in irrigating farming.