Soil Carbon Dynamics in Complex Agroecosystems of Latin America

OELBERMANN, M.; DYER, L.; ECHARTE, L.; ESMAIL, S

Saskatoon

Encuentro; Canadian Society of Soil Science Annual meeting in Saskatoon, Saskatchewan; 2010

The conversion of forests and natural grasslands to agricultural production systems has accelerated the mineralization of soil organic carbon (SOC). The objectives of this paper are to outline the most recent findings on the potential of complex agroecosystems in Latin America to sequester C and to greenhouse gas production rates.  Results showed that an 18-year old agroforestry system with E. poeppigiana in Costa Rica increased its SOC at a rate of 1.1 Mg C ha-1 y-1 (40 cm).  Soil from a Costa Rican silvopasture was not significantly different in C and N concentrations with time, but that of a conventional pasture decreased significantly with time.  Correspondingly, soil microbial community structure, species diversity and richness were not significantly different in the silvopastoral system.  We also observed that landowners in Costa Rica readily implemented agroforestry practices for soil conservation and C sequestration, especially as part of a payment for ecological services (PES). These landowners also noted a greater resilience of agroforestry systems during intense dry seasons.  Preliminary results after the first three years of maize-legume intercropping in Argentina showed no significant differences in SOC content between the intercrop and maize or soybean sole crops two years after initiating these experiments.  However, results showed that maize-legume intercropping systems had a significantly greater soil microbial biomass C compared to either sole crop maize or soybean treatments.  Greenhouse gas production rates, over a 3-year period, showed no significant differences between treatments for CO2, but the intercrops had significantly lower N2O production rates compared to the sole crops.  Results for CH4 were variable.  Research in Latin America suggests that over time, complex agroecosystems have the potential to sequester C, mitigate GHG production rates and show greater resilience to global warming compared to conventional agroecosystem land management practices.