The complex synthesis process, low utilization, and single
function
of fungicides have seriously hindered the development of fungicides
in resistance to rice sheath blight. Here, an inexpensive and multifunctional Cu(II)-based water-dispersible
humic acid (Cu-WH) fungicide with growth-promoting ability was developed
with a simple method. A 3D molybdate carbon hierarchical nanosphere
(MoO2-C-HN) catalyst was successfully synthesized using
a green route and applied in a solid-phase activation of lignite to
obtain water-dispersible humic acid. Cu(II)-based water-dispersible
humic acid (Cu-WH) was then formed through a simple reaction of Cu(II)
and the humic acid. The resultant Cu-WH showed strong antifungal performance
against Rhizoctonia solani in laboratory incubation
experiments. After being treated with Cu3-WH (0.1 mg L–1), the control efficiency of rice sheath blight at 1, 3, and 5 days
after infection was 90.54%, 78.96%, and 66.31%, respectively. It also
enhanced the water-holding capacity of the substrate and thus effectively
improved the growth of rice seedlings. In comparison to commercial
rice seedling substrate, the substrate treated with 8 wt % of Cu3-WH
increased plant height, stem diameter, fresh weight, and chlorophyll
content by 19.23%, 35.91%, 14.52%, and 42.85%, respectively. The newly
developed Cu-WH thus can be used as a novel low-cost efficient fungicide
and growth stimulator to treat rice sheath blight as well as to increase
rice production.