Abstract

Soil of the former lake Texcoco is nitrogen (N) depleted, so any attempt to vegetate the area will require the application of an N fertilizer. Urea is commonly used as fertilizer, but its application to soil might affect emissions of greenhouse gases (GHG), such as carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4), and the high pH and electrolytic conductivity (EC) in the Texcoco soil might inhibit the hydrolysis of urea. Four soils of the former lake bed with EC 3.3, 88.3, 96.9, and 121 dS m-1, were amended with urea while dynamics of mineral N and emissions of GHG were monitored. Urea increased emission of CO2 in all soils and emission of N2O in soil with EC≤88.3 dS m-1, but emission of CH4 was not affected. Hydrolysis of urea occurred in all soils although it was significantly lower in soil with EC≥88.3 dS m-1. Oxidation of NH4+ occurred in soil with EC≤96.9 dS m-1, but oxidation of NO2- only in soil with EC 3.3 dS m-1. It was found that oxidation of NH4+ and NO2-, and hydrolysis of urea was inhibited by the high EC in soil of the former lake bed, while emissions of CO2 and N2O, but not CH4 were affected by application of urea.

Key words: Carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4), former lake bed, mineral N in soil.