Browsing by Author "de Varennes, A."
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- A climate change scenario and soil ammonium “fixation” during the seasonal rice (Oryza sativa) growth in Portugal under intermittent floodingPublication . Figueiredo, N.; Carranca, C.; Coutinho, J.; Trindade, H.; Pereira, J.; Marques, P.; de Varennes, A.The “newly fixed” NH4 + in clay minerals should be considered for an efficient management of plant nutrition. In a clayloam 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.
- A dinâmica do azoto mineral no solo e na lâmina de água, em resposta a diferentes condições ambientaisPublication . Figueiredo, N.; Trindade, H.; Pereira, J.; Coutinho, J.; Goufo, P.; Prazeres, A.; Marques, P.; de Varennes, A.; Carranca, C.
- Elevated carbon dioxide and temperature effects on rice yield, leaf greenness, and phenological stages durationPublication . Figueiredo, N.; Carranca, C.; Trindade, H.; Pereira, J.; Goufo, P.; Coutinho, J.; Marques, P.; Maricato, R.; de Varennes, A.Abstract The present field experiment was conducted during two consecutive cropping seasons in central Portugal to study the effects of simultaneous elevation of carbon dioxide concentration ([CO2]) (550 lmol mol-1 ) and air temperature (?2–3 C) on japonica rice (Oryza sativa L. ‘‘Ariete’’) yield, crop duration, and SPAD-values across the seasons compared with the open-field condition. Open-top chambers were used in the field to assess the effect of elevated air temperature alone or the combined effect of elevated air temperature and atmospheric [CO2]. Open-field condition was assessed with randomized plots under ambient air temperature and actual atmospheric [CO2] (average 382 lmol mol-1 ). Results obtained showed that the rice ‘‘Ariete’’ had a moderate high yielding under open- field condition, but was susceptible to air temperature rise of ?2–3 C under controlled conditions resulting in reduction of grain yield. The combined increase of atmospheric [CO2] with elevated air temperature compensated for the negative effect of temperature rise alone and crop yield was higher than in the open-field. SPAD-readings at reproductive stage explained by more than 60 % variation the straw dry matter, but this finding requires further studies for consolidation. It can be concluded that potential increase in air temperature may limit rice yield in the near future under Mediterranean areas where climate change scenario poses a serious threat, but long term field experiments are required.
- Produção e valores de SPAD na cultura do arrozPublication . Figueiredo, N.; Carranca, C.; Trindade, H.; Pereira, J.; Goufo, P.; Coutinho, J.; Marques, P.; Maricato, R.; de Varennes, A.