Magnesium plays a crucial role in plant physiological processes. However, the specific mechanisms underlying the response of tea plants to altered magnesium nutrition under acid stress remain unclear. This study investigates how root environment acidification impacts tea seedlings and the role of magnesium (Mg) in mitigating these effects. We examine varying pH and Mg levels’ influence on tea seedlings’ resistance to abiotic stress, focusing on antioxidant capacity and nutritional content. In a hydroponic experiment, we varied root pH (3.5, 5.0, 6.5) and Mg concentrations (0.01, 0.4, 0.8 mM), assessing parameters like antioxidant capacity, peroxidative damage, and nutritional content at 1, 7, 15, and 30 days post treatment. Root environment acidification and Mg deficiency worsened peroxidative damage in tea plant leaves and roots. Increased Mg supplementation enhanced antioxidant enzyme activity, reducing malondialdehyde and mitigating oxidative damage from root environment acid stress. Under acid stress, 0.8 mM Mg significantly increased tea leaf polyphenols, amino acids, and water-soluble extracts. Mg notably boosted chlorophyll content, surpassing lower Mg levels at pH 5. Additionally, Mg reversed root vitality inhibition induced by acid stress, leading to increased nitrogen, potassium, and Mg concentrations in leaves, promoting balanced nutrient absorption. Mg supplementation is crucial for enhancing tea plant antioxidant capacity, alleviating growth inhibition from root-environment acid stress, and improving chlorophyll content and root vitality, highlighting Mg’s significance in tea cultivation and broader agricultural practices.

Soil acidification in tea plantations leads to an excessive heavy metal content in tea, decreasing its yield and quality. How to apply shellfish and organic fertilizers to improve soil and ensure the safe production of tea is still not clear. A two-year field experiment was conducted in tea plantations in which the soil was characterized by a pH of 4.16 and concentrations of lead (Pb) (85.28 mg/kg) and cadmium (Cd) (0.43 mg/kg) exceeding the standard. We used shellfish amendments (750, 1500, 2250 kg/ha) and organic fertilizers (3750, 7500 kg/ha) to amend the soils. The experimental results showed that compared with the treatment without any amendment (CK), the soil pH increased by 0.46 on average; the soil available nitrogen, phosphorus, and potassium contents increased by 21.68%, 19.01%, and 17.51% respectively; and the soil available Pb, Cd, Cr, and As contents decreased by 24.64%, 24.36%, 20.83%, and 26.39%, respectively. In comparison to CK, the average yield of tea also increased by 90.94 kg/ha; tea polyphenols, free amino acids, caffeine, and water extract increased by 9.17%, 15.71%, 7.54%, and 5.27%, respectively; and the contents of Pb, Cd, As, and Cr in the tea decreased significantly (p < 0.05) by 29.44–61.38%, 21.43–61.38%, 10.43–25.22%, and 10.00–33.33%, respectively. The greatest effects on all parameters occurred with the largest amendment of both shellfish (2250 kg/ha) and organic fertilizer (7500 kg/ha) combined. This finding suggests that the optimized amendment of shellfish could be used as a technical measure to improve the health quality of both soil and tea in acidified tea plantations in the future.

Industrialization and urbanization have produced large amounts of atmospheric and soil pollutants. Among them, heavy metals are one of the main byproducts that are widely distributed in the atmosphere, water, soil and organisms, which have a great impact on climate. It is of great significance to reduce their enrichment in soil by ecological restoration methods for the sustainable development of urban atmosphere and climate. This study investigated the effects of different garden plants (Festuca arundinacea, Ageratum conyzoides, Trifolium repens) mixed with Brassica parachinensis on plant growth, physiological indexes and Cr (chromium) content in aboveground and underground parts in Cr (the main heavy metal pollution produced by industrialization) contaminated soil. The yield of B. parachinensis was the highest under the mixed cropping mode with T. repens, with the Cr content in edible parts being lower than the standard, suggesting an effective combination of B. parachinensis in community gardens. The mixed cropping of F. arundinacea with Bra decreased B. parachinensis yield. Under the mixed cropping of A. conyzoides, the edible parts of B. parachinensis were aggravated by Cr pollution, which was not recommended for planting. Our results suggest that converting the monoculture mode of vegetables to mixed cropping with garden plants reduced heavy metal pollution of community garden plants and improved soil productivity and environmental quality.