Soil acidification in a continuous cotton production system

Effects of nitrogen (N) fertilization on soil organic carbon (SOC) and total N are well established, but their effects on soil acidification and emerging soil health indicators such as labile N and carbon (C) pools are not adequately documented. This research evaluated soil N and C pools and soil pH with long-term N management in continuous cotton (Gossypium hirsutum L.) production. Residual soil inorganic N, potentially mineralizable N and C, total N, SOC, pH, and electrical conductivity were measured after 17 yr of continuous N application. Comparison of five N rates (0, 56, 112, 168, and 224 kg ha^–1) showed an increase in residual inorganic N pools and decrease in pH with an increase in N application rate, while other parameters did not change significantly. Soil acidification was significant with 168 and 224 kg N ha^–1 rates. Soil pH dropped by 0.039 per kilogram increase in residual inorganic N. Optimizing N rate that minimizes residual inorganic N can reduce soil acidification.