Resumo

FIGUEIREDO, Nuno et al. A climate change scenario and soil ammonium “fixation” during the seasonal rice (Oryza sativa) growth in Portugal under intermittent flooding. Rev. de Ciências Agrárias [online]. 2013, vol.36, n.4, pp.455-465. ISSN 0871-018X.

The “newly fixed” NH₄⁺ in clay minerals should be considered for an efficient management of plant nutrition. In a clay-loam soil cultivated in 2012 with rice under intermittent flooding and conventional agronomic practices, the dynamics of pH, N-inorganic and non-exchangeable NH₄⁺ was evaluated i) under field conditions, air temperature and atmospheric [CO₂] (375 µmol mol^-1 air) in Salvaterra de Magos (Portugal), and ii) under elevated temperature and temperature+[CO₂] in controlled microclimate. For that, open-top chambers were used to simulate the conditions of an increased mean air temperature (2-3 °C), alone or combined with increased [CO₂] (550 µmol mol^-1 air). Non-exchangeable NH₄⁺ was significantly higher under open-field conditions compared with the temperature elevation, with or without elevated atmospheric [CO₂]. Temperature elevation reduced the “fixation” rate of the cation, while the CO₂ concentration rise did not affect particularly the non-exchangeable form. Further studies are required for consolidation of these findings together with microbial communities and dynamics of C and N in soil.

Palavras-chave : Atmospheric CO₂; clay loam soil; controlled environment; open-field; temperature.

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