Effects of Different Nitrogen Fertilizer Rates on Soil Magnesium Leaching in Tea Garden

Magnesium (Mg) helps improve tea yield and quality, yet many tea plantations in China commonly exhibit magnesium deficiency. Therefore, studying the mechanisms of Mg²⁺ leaching in tea plantation soils is of significant importance. This study investigates how nitrogen fertilizer application affects the leaching mechanisms of magnesium in soil through pot experiments. The control group (N0) consisted of pots without tea seedlings and no nitrogen fertilizer solution added, only an equivalent amount of ultrapure water was used. The experimental groups were: N1 (no tea seedlings, 0.75 mmol L^− 1 nitrogen), N2 (no tea seedlings, 1.5 mmol L^− 1 nitrogen), N3 (no tea seedlings, 3.0 mmol L^− 1 nitrogen), TN0 (tea seedlings, no nitrogen), TN1 (tea seedlings, 0.75 mmol L^− 1 nitrogen), TN2 (tea seedlings, 1.5 mmol L^− 1 nitrogen), and TN3 (tea seedlings, 3.0 mmol L^− 1 nitrogen). The results show that the correlation between nitrate nitrogen (NO₃⁻-N), ammonium nitrogen (NH₄⁺-N), and Mg in the soil with tea seedlings is higher than in soil without tea seedlings. This indicates that tea planting promotes the leaching of Mg²⁺ in the soil. Further investigation revealed that excessive nitrogen application reduces the soil pH, activates aluminum ions (Al³⁺) in the soil, and competes with Mg²⁺ for net adsorption sites, further exacerbating the leaching of Mg²⁺. Additionally, excessive use of nitrogen fertilizer limits the roots’ ability to absorb nutrients, indirectly leading to the leaching of Mg²⁺. We believe that excessive application of nitrogen fertilizer in tea gardens will exacerbate the leaching of Mg²⁺ in the soil.