Every year, approximately 2 billion tons of plant-derived waste (such as straw and crop residues) are generated globally, most of which are either incinerated, dumped, or landfilled without proper planning, leading to severe environmental pollution and resource wastage. Plant-derived waste exhibits potential advantages as a growing media component in various aspects. However, numerous studies have also indicated that plant-derived waste generally possesses strong phytotoxicity, which must be removed or reduced before being utilized as a growing media component. Therefore, accurately assessing their phytotoxicity and appropriately modifying it to ensure their support for plant growth when used as a growing media component is crucial. This paper reviews the manifestation and assessment methods of phytotoxicity in plant-derived waste; systematically summarizes the phytotoxicity sources of three common types of plant-derived waste (garden waste, crop straw, and spent mushroom substrate), as well as the toxic mechanisms of two representative phytotoxic substances (phenolic compounds and organic acids); and proposes some insights into further research directions. By consolidating insights from these studies, this review aims to deepen our understanding of phytotoxicity and its implications, and offer valuable references and guidance for future research endeavors and practical applications.

Wood fiber substrates are widely used as peat substitutes in horticulture, but the impact of their high carbon-to-nitrogen ratio on nitrogen immobilization and crop photosynthetic performance remains unclear. This study systematically examined the effects of wood fiber substrates on lettuce photosynthetic performance and underlying physiological mechanisms using pot experiments. Two substrate treatments—peat (control) and wood fiber—were combined with three nitrogen levels: low, medium, and high (63, 127, and 210 mg N·L⁻¹). Results indicated that wood fiber substrates significantly reduced the availability of fast-acting nitrogen, leading to a substantial decrease in lettuce biomass (39.0–56.8%), total nitrogen content (7.2–39.9%), and chlorophyll content (13.7–36.2%). Chlorophyll fluorescence kinetics analysis revealed that wood fiber substrates impair photosystem function through multiple pathways. At the early stage (15 days), key effects included structural damage to the donor side of PSII(Photosystem II), indicated by L and K peaks, and inhibited electron transfer on the PSI(Photosystem I) acceptor side (δRo decreased by 15.08–27.90%, along with a reduction in W_OI amplitude). The findings provide an important theoretical basis for optimising nitrogen management strategies for wood fibre substrates.

The rapid growth of the horticultural industry has increased demand for soilless cultivation substrates. Peat, valued for its physical and chemical properties, is widely used in soilless cultivation. However, peat is non-renewable, and over-extraction poses serious ecological risks. Therefore, sustainable alternatives are urgently needed. Ammonium incubation, a novel method to reduce phytotoxicity, offers the potential for green waste, a significant organic solid waste resource, to substitute peat. This study optimized the ammonium incubation process to reduce green waste phytotoxicity. It systematically examined different nitrogen salts (type and amount) and environmental conditions (temperature, aeration, duration) affecting detoxification efficiency. Results show a significant reduction in phytotoxicity with ammonium bicarbonate, carbonate, and sulfate, especially carbonate, at 1.5%. Optimal conditions were 30 °C for 5 days with regular aeration. Under these conditions, ammonium salt-treated green waste significantly reduced total phenolic content and stabilized germination index (GI) at a non-phytotoxic level (127%). Using treated green waste as a partial peat substitute in lettuce cultivation showed promising results. This low-cost, low-energy method effectively converts green waste into sustainable peat alternatives, promoting eco-friendly horticulture and environmental conservation.