Exploration of metal-organic framework (MOF) material as a new type of fertilizer applied in rice

Objectives Metal-organic framework (MOF) is a new type of cluster functional compound based on molecular design, which provides a new idea for the design of new type of fertilizers. Two MOF materials were synthesized under hydrothermal conditions, and their availability as fertilizer was testified.

Methods FeCl₃·6H₂O, ZnSO₄·7H₂O, H₃PO₄, H₂C₂O₄·2H₂O and CO (NH₂)₂ were used as basal reactants, and reaction was conducted inside reactors at 100℃. Two MOFs, i.e., MOF1 and MOF2 were designed, the nutrient composition in MOF1 and MOF2 was: Fe 18.6% and 15.6%; P 15.7% and 16.5%, N 5.16% and 4.57%, C 4.61% and 5.21%, Zn 0 and 2.89%, respectively. A field experiment was conducted using the two MOFs, as well as a conventional fertilizer (CF) as treatments and a no fertilizer control (CK). The three fertilizer treatments had the same NKP input rate (N 150 kg/hm², P₂O₅ 200 kg/hm²and K₂O 150 kg/hm²) and fertilization method. At tillering, jointing, booting and ripening stage of rice, tillage layer soil samples (0–20 cm) were collected, and ammonium nitrogen, nitrate nitrogen, available P, available Fe, available Zn and pH were determined. At harvest, the grain yield, 1000-kernel weight, the number of kernels per ear, the number of effective ears and seed-setting rate of rice were investigated.

Results Compared with the CF, the grain yields of MOF1 and MOF2 were increased by 7.7% and 6.3%, respectively, and the relevant agronomic traits were also improved. The total dry matter and N accumulation in MOF1 and MOF2 were significantly higher than those in CF; the nitrogen utilization rate in CF was 32.8%, whereas in MOF1 and MOF2 were 46.4% and 43.0%. At the mature stage, the soil ammonium nitrogen, nitrate nitrogen and available Fe content in MOF1 and MOF2 were also significantly higher than those in CF.

Conclusions The new type of fertilizers with MOF frames demonstrates the effectiveness in improving grain yield, nitrogen utilization efficiencies and soil nutrient contents. So MOF could be an alternative option for the development of new type of fertilizers.