Exploring the role of sewage phosphorus-recycling ceramsite in promoting hydroponic growth of narcissus: Mechanistic insights

Abstract

Adsorption methods are widely applied in the field of sewage treatment, particularly concerning, the disposal of adsorbents as solid wastes, which has attracted considerable attention. One potential approach is to harmlessly utilize these materials as substrates for soilless cultivation. Nevertheless, the effects on plant growth and the underlying mechanisms of using sewage adsorbent-recycling materials as soilless cultivation substrates remain unclear. Clarifying these aspects is crucial for assessing the feasibility of reusing adsorbent-recycling materials. This study conducted soilless cultivation experiments on narcissus using phosphorus-recycling ceramsite (PC) after adsorption treatment of phosphorus-containing sewage to investigate its impact on plant growth. The results indicated that compared to commercial ceramic granules and control experiments, PC significantly promoted the growth of narcissus. Specifically, the average leaf lengths of narcissus in PC cultivation were 1.77- and 1.40-fold longer than in the control and commercial ceramic granule treatments after 30 d, respectively. The effects and contributions of various hydroponic solution indicators were assessed through Mantel analysis, Spearman correlation analysis, and random forest algorithm. The findings confirmed that phosphorus content and pH in the hydroponic solution had a substantial impact on narcissus growth (p < 0.01). Additionally, bioactive substances in the hydroponic solution were detected by three-dimensional fluorescence excitation-emission spectroscopy (3D-EEM) and LC-MS. In summary, the mechanisms by which PC promotes narcissus growth primarily include: environmental stress on roots was reduced by PC by providing essential mineral elements and phosphorus to the hydroponic solution while mitigating pH decline; the accumulation of autotoxic substances such as cinnamic acid and apoptosis-inducing substances like stachyose in the hydroponic solution is inhibited, while the production of growth-promoting substances is enhanced; microbial content in the hydroponic solution is reduced to minimize toxicity and competitive effects. This study not only proposes new insights into the mechanism of hydroponic substrates affecting narcissus growth but also offers new perspectives for the harmless reuse of adsorbed solid waste.