Effects of Biochar and α-Fe2O3 Nanoparticles on the Growth, Photosynthetic Apparatus and Fruit Quality of Medicinal Plant Muskmelon

Agricultural soils are facing problems such as water scarcity and nutrient loss. Compared to traditional chemical fertilizers, biochar and nanomaterials may become new options for agricultural soil improvement. However, when faced with new soil amendments, the response of medicinal plants may not necessarily meet expectations. In this study, we evaluated the effects of biochar and nano iron oxide as soil modifiers, both alone and in combination, on the growth, physiology, and fruit quality of muskmelon (Cucumis melo L.). The results showed that the composite treatment enhanced the stem crude increase of muskmelon from the vegetative period to flowering period, and also increased leaf pigment content at the fruiting period. Each treatment also significantly promoted the photosynthesis of muskmelon, which increased the ΦPSII values at flowering period by 30.77, 80.77 and 73.08%, respectively, compared with the control group. But the contents of medicinal ingredients in the fruit pulp and seeds of each treatment group were significantly negatively affected. The polyphenol and saponin contents of seeds were decreased in each treatment group, as was the accumulation of saponins in the fruit pulp. It is indicated that soil amendments may decrease the contents of medicinal ingredients and reduce the quality of muskmelon fruits while promoting the growth of medicinal plants. Our study raises risk warnings for the selection of soil amendments in medicinal plant cultivation.