Chemical and biological characteristics of alkaline saline soils from the former Lake Texcoco as affected by artificial drainage
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Soils from the former Lake Texcoco are alkaline saline and were artificially drained and irrigated with sewage effluents since the late 1980s. Undrained soil and soil drained for 1, 5 and 8 years were sampled, characterized and incubated aerobically for 90 days at 22±1 °C while production of CO2, available P and concentrations of NH4+, NO2– and NO3– were monitored. Artificial drainage decreased pHH2O, water holding capacity, organic C, total N, and Na+, K+, Mg2+, B, Cl– and SO42– concentrations, increased inorganic C and Ca2+ concentrations more than 5-fold while total P was not affected. Microbial biomass C decreased with increased length of drainage but bacteria, actinomycetes, denitrifiers and cellulose-utilizing bacteria tended to show opposite trends. CO2 production was less in soils drained ≥5 years compared to undrained soil but more than in soils drained for 1 year. Emission of NH3 was negligible and concentrations of NH4+ remained constant over time in each soil. Nitrification, as witnessed by increases in NO3– concentrations, occurred in soil drained for 8 years. NO2– concentrations decreased in soils drained ≤1 year in the first 7 days of the incubation and remained constant thereafter. It was found that artificial drainage of soils from the former Lake Texcoco profoundly affected soil characteristics. Decreases in pH and Na+, K+, Cl– and SO42– concentrations made conditions more favourable for plant growth, although low concentrations of inorganic N and available P might be limiting factors.
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