Impact of different fertilizers on carbonate weathering in a typical karst area, Southwest China: a field column experiment
- 1The Institute of Hydrogeology and Environmental Geology, Chinese Academy of Geological Sciences, Shijiazhuang, 050803, Hebei, China
- 2School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing, 100083, China
Abstract. Carbonate weathering, as a significant vector for the movement of carbon both between and within ecosystems, is strongly influenced by agricultural fertilization, since the addition of fertilizers tends to change the chemical characteristics of soil such as the pH. Different fertilizers may exert a different impact on carbonate weathering, but these discrepancies are as yet not well-known. In this study, a field column experiment was conducted to explore the response of carbonate weathering to the addition of different fertilizers. We compared 11 different treatments, including a control treatment, using three replicates per treatment. Carbonate weathering was assessed by measuring the weight loss of limestone and dolostone tablets buried at the bottom of soil-filled columns. The results show that the addition of urea, NH4NO3, NH4HCO3, NH4Cl and (NH4)2CO3 distinctly increased carbonate weathering, which was attributed to the nitrification of NH4+. The addition of Ca3(PO4)2, Ca–Mg–P and K2CO3 induced carbonate precipitation due to the common ion effect. The addition of (NH4)3PO4 and NaNO3 had a relatively small impact on carbonate weathering in comparison to those five NH4-based fertilizers above. The results of NaNO3 treatment raise a new question: the negligible impact of nitrate on carbonate weathering may result in an overestimation of the impact of N fertilizer on CO2 consumption by carbonate weathering on the regional/global scale if the effects of NO3 and NH4 are not distinguished.