Multi-Batch Consecutive Foliar Spraying Zinc–Carbon Dot Nano-Fertilizer Improving Soil Health for Bok Choy Cultivation Production

This study represents the first evaluation of the effects of zinc-carbon dot nano-fertilizers (Nano-ZCDs) on the growth of Bok choy (<i>Brassica chinensis</i> L.) and soil health under multi-batch consecutive foliar spraying during three successive cultivation cycles. The results showed that relative to CK, Nano-ZCDs significantly elevated the fresh weight of Bok choy cultivation across three consecutive harvests, by 75.5 ± 1.8%, 75.1 ± 0.2%, and 74.6 ± 0.4%, respectively. Meanwhile, the nutritional value, including amino acids, vitamin C, soluble sugars, proteins, and Zn accumulation, was markedly enhanced by Nano-ZCDs. Additionally, Nano-ZCDs significantly improved soil water content, Eh, soil organic carbon, available potassium, and available phosphorus in the rhizosphere soil. It also enhanced the complexity, stability, and species richness of the bacterial community. Based on the Cornell Soil Health Assessment system, the soil health index of the Nano-ZCDs group was significantly 8.1% higher than that of the CK group. Therefore, multi-batch consecutive applying of Nano-ZCDs promoted Bok choy cultivation growth and improved its quality, without impairing soil health. This study suggests that Nano-ZCDs can be applied in agricultural production processes to promote the sustainable development of agricultural systems.