Effects of Different Nursery Substrates on the Growth Physiology and Rhizosphere Microorganisms of Two Species of Ornamental Bamboo

The cultivation of ornamental bamboos in pots and gardens has a higher demand for light and clean cultivation substrates, and the effects of such cultivation substrates on the growth of ornamental bamboos are rarely seen. In this study, we compared the effects of physicochemical properties of different cultivation substrates on the growth physiology of ornamental bamboos and analysed the composition of rhizosphere microbial communities by cultivating Pleioblastus chino f. holocrysa (PC), and Arundinaria fortune (AF), in both common soil (CS) and soilless substrate (SS). In PC and AF, compared to biomass at the start of cultivation the aboveground biomass of CS and SS increased by 13.71% and 0.81%, the root biomass increased by 16.01% and 25.52%, and the bamboo whip biomass decreased by 29.72% and 24.75% at the end of the cultivation. In both PC and AF, the abundance of Proteobacteria in SS (42.28% and 48.42%, respectively) was higher than in CS (38.52% and 34.92%, respectively), the abundance of Ascomycota in SS (76.55% and 87.89%, respectively) was higher than that of CS (72.46% and 68.80%, respectively), the abundance of Bacteroidota in SS (10.35% and 9.16%, respectively) was higher in CS (7.42% and 7.61%, respectively), and was positively correlated with organic matter and available nitrogen, phosphorus, and potassium. The abundance of beneficial microbial genera (Haliangium, Acidibacter, BIrii41, Pseudeurotium) increased in SS, and the abundance of pathogenic fungi Fusarium in SS (1.87% and 0.10%, respectively) was lower than in CS (3.97% and 3.10%, respectively). Taken together, the results reveal that SS increased the growth of aboveground parts of ornamental bamboo, inhibited the growth of bamboo whips, and reduced the allocation of biomass to foraging organs compared with CS. The increase in beneficial microbial genera promoted the development of the root system and the accumulation of nitrogen, phosphorus, and potassium in the leaves of ornamental bamboo, and the decrease in pathogenic genera lowered the risk of disease infection in the ornamental bamboo.