Influence of Nitrogen Fertilizer Application on Soil Acidification Characteristics of Tea Plantations in Karst Areas of Southwest China

Nitrogen (N) fertilizer application is one of the causes soil acidification at tea plantations. However, effect N on characteristics plantations with different acidities remains unclear. In this study, field experiments were conducted to investigate effects nitrogen rates pH, pH buffer capacity (pHBC), exchangeable total acidity (ETA), base cations (EBCs), and cation exchange (CEC) in topsoil non-acidified (NA), mildly acidified (MA), heavily (HA) The results showed that Al3+ (E-Al) CEC HA > MA NA all plantations, whereas EBCs saturation percentage (BSP) < NA. 4.0, EBCs, BSP decreasing trends increasing application, E-Al an trend. a small trend increase H+ (E-H), E-Al, trends. Meanwhile, range 4–6, acid–base curve rose sharply, excessive (N900) significantly reduced pHBC. addition, stepwise regression analysis BSP, Mg2+ (E-Mg) had significant direct conclusion, decrease main mechanisms caused by was cause exacerbated