*2.2.5 Intensive nitrogen fertilization*

Intensive NH4 + input can replace the base cations such as Ca2+, Mg2+, K+ , and Na<sup>+</sup> and accelerate leaching, reducing the pH buffering capacity of top soil [59]. Hydrolysis of soil NH4 + will generate NH3 (gas) and consume an OH<sup>−</sup> (NH4 + + OH<sup>−</sup> = NH3↑ + H2O) [60].

Acidic fertilizers such as Ca(H2PO4)2 will gradually release H<sup>+</sup> , hence increasing soil acidification (Ca(H2PO4)2 → CaHPO4 + H3PO4, H3PO4 → H+ + H2PO4 → 2H+ + HPO4 <sup>2</sup><sup>−</sup> → 3H+ + PO4 <sup>3</sup><sup>−</sup>).
