Browsing by Author "Carranca, C."
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- A alteração climática na “fixação” do amónio em solos cultivados com arroz (Oryza sativa) por alagamentoPublication . Figueiredo, N.; Carranca, C.; Coutinho, J.; Trindade, H.; Pereira, J.; Prazeres, A.; Marques, P.O arroz, é essencialmente produzido como monocultura, em canteiros alagados, nas regiões do centro e sul do País (Vales do Mondego, Tejo e Sado). O ião NH4 + é a forma de N mineral mais abundante e preferencialmente absorvida pelo arroz, em condições de alagamento. O alagamento potencia a mineralização, por acção dos microrganismos aeróbios facultativos, aumentando a sua concentração na solução do solo. No solo, este catião pode ser adsorvido nos colóides ou "fixado" nos minerais argilosos do tipo 2:1, tornando-se temporariamente indisponível para a cultura. A taxa de "fixação" e posterior libertação para a solução depende da textura do solo, do teor e mineralogia da argila, pH, potencial redox, temperatura e presença de outros catiões. Não se conhecem os efeitos do aumento simultâneo da concentração de CO2 na atmosfera e da temperatura na "fixação" do NH4 + , sabendo-se que, isoladamente, o aumento da temperatura potencia a "fixação". Neste estudo, avaliou-se o teor de NH4 + em dois solos (areno-franco e argilo-limoso) alagados e cultivados com arroz, em 2012, como resposta à fertilização mineral e ao alagamento. Compararam-se esses teores com os medidos no solo argilo-limoso, em condições controladas de aumento da [CO2] e temperatura. O teor de NH4 + "fixado" em ambos os solos (ar livre) foi superior ao da concentração de NH4 + disponível no respectivo solo. A concentração de NH4 + "fixada" no solo argilo-limoso manteve-se superior à do solo arenofranco, variando com os tratamentos (ar livre > CO2+temperatura = temperatura), com as datas de amostragem e com a fertilização azotada.
- 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.
- O cultivo do arroz em Portugal e a resposta do agrossistema às alterações ambientais de temperatura e concentração de dióxido de carbonoPublication . Figueiredo, N.; Menino, R.; Prazeres, A.; Fareleira, P.; Vargues, A.; Carranca, C.; Marques, P.; Pereira, J.; Goufo, P.; Trindade, H.; Carneiro, J.; Couto, N.; Mateus, E.; Ribeiro, A.; Coutinho, J.
- 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.
- Effect of elevated carbon dioxide (CO2) on phenolic acids, flavonoids, tocopherols, tocotrienols, γ-oryzanol and antioxidant capacities of rice (Oryza sativa L.)Publication . Goufo, P.; Pereira, J.; Figueiredo, N.; Oliveira, M.; Carranca, C.; Rosa, E.; Trindade, H.There have been no studies conducted with the objective of investigating the effect of elevated CO2 concentrations ([CO2]) on antioxidants in grains. Therefore, a two-year field experiment was conducted using open-top chambers with two levels of atmospheric CO2 (375 and 550 mmol/mol) to evaluate their effects on rice grain antioxidants. Following exposure to high [CO2], the total phenolic content of all rice milling fractions decreased (3%e18%), with the highest reduction in the brown rice for sinapic acid (167%), and in the white rice for p-hydroxybenzoic acid (100%). The total flavonoid content also decreased under elevated [CO2] in all rice milling fractions (8%e14%), with apigenin (25%) being highly affected in the white rice, and tricin (12%) in the bran. The same trend was found for g-oryzanol, with decreases of 35%, 32%, 25%, and 2% in the white rice, brown rice, husk, and bran, respectively. In the white and brown rices, tocopherols and tocotrienols were all lower under elevated [CO2], with reductions larger for a-tocotrienol (69%), g-tocotrienol (46%), and a-tocopherol (38%). Good correlations between antioxidant contents and DPPH radical scavenging capacities indicated that these decreases may be meaningful in the preventive ability of rice against free radical-mediated degenerative diseases
- Effects of elevated temperature and atmospheric carbon dioxide concentration on the emissions of methane and nitrous oxide from Portuguese flooded rice fieldsPublication . Pereira, J.; Figueiredo, N.; Goufo, P.; Carneiro, J.; Morais, R.; Carranca, C.; Coutinho, J.; Trindade, H.Methane (CH4) and nitrous oxide (N2O) emissions from flooded rice fields have been rarely measured in Europe. A field study was carried out in an intermittent flooded rice field at central Portugal to investigate if global warming under Mediterranean conditions, elevated soil temperature (þ2 $C) and atmospheric [CO2] (550 ppm), could lead to significant effects in CH4 and N2O emissions. The experimental design consisted of three treatments arranged in a randomized complete block design with three replicates. To assess the effects of ambient temperature and actual atmospheric [CO2] (375 ppm), plots were laid under open-field rice conditions. Using open-top chambers, two other treatments were established: one to assess the effect of elevated temperature and actual atmospheric [CO2] and a third treatment to evaluate the combined effect of elevated temperature and atmospheric [CO2]. Measurements of CH4 and N2O fluxes were made throughout two consecutive growing seasons in the field using the closed chamber technique. Elevation of temperature with or without elevated atmospheric [CO2] increased CH4 emissions by 50%, but this increase was not significant compared to the open-field condition. As for N2O, elevated temperature alone or combined with elevated atmospheric [CO2] had no significant effect on emissions relative to the open-field treatment. The estimated seasonal CH4 EF for the Portuguese flooded rice fields was 10.0 g CH4 m"2 , while the EF for N2O emissions was 1.4% of N input. These results suggested that default seasonal CH4 and N2O EFs currently used by the Portuguese inventory were not appropriated.
- 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.
- Impact of agricultural practices, elevated temperature and atmospheric carbon dioxide concentration on nitrogen and pH dynamics in soil and floodwater during the seasonal rice growth in PortugalPublication . Figueiredo, N.; Carranca, C.; Goufo, P.; Pereira, J.; Trindade, H.; Coutinho, J.Data on the movements of available N and non-exchangeable NH4 + in the soil are of crucial importance in designing an efficient plant N nutrition management scheme in paddy rice fields. To investigate the processes affecting the dynamics of N and pH under Mediterranean conditions, rice (Oryza sativa L. cv. Ariete) was cultivated in 2011 and 2012 in Salvaterra de Magos (central Portugal) under the following climate scenarios: (i) ambienttemperature and ambient [CO2] in the open-field, (ii) elevated temperature (+3 C) and ambient [CO2] in open-top chambers, and (iii) elevated temperature (+3 C) and elevated [CO2] (+175mmol mol1 ) in open-top chambers. Plants were grown under an intermittent flooding regime. Soil and water samples were taken at eight different stages of plant growth, including before and after N basal and topdressing. Our study indicated that the processes underlying N changes in response to the timing of N fertilization were different depending on the N form. After basal dressing under aerobic conditions, both available and non-exchangeable NH4 + contents were increased. Following the topdressing under flooded conditions, the available content of soil N increased, whereas the non-exchangeable NH4 + content decreased. A negative relationship was found between soil pH and NH4 + “fixation” when roots were active, and vice-versa. Elevated temperature alone or in combination with elevated [CO2] had no effect on the total available N content in the soil and floodwater. Under elevated temperature, however, the non-exchangeable NH4 + content was significantly reduced (11%), with the same magnitude of change (10%) observed under co-elevation of temperature and [CO2]. These results suggested that non-exchangeable NH4 + in paddy fields might be insensitive to [CO2] elevation under Mediterranean conditions, while reductions observed under co-elevation of [CO2] and temperature might be associated with temperature alone. This information could be used to alter rice management practices and to adjust N application under climate change.
- Influence of agricultural practices and climate changes in Portuguese rice productionPublication . Figueiredo, N.; Carranca, C.; Trindade, H.; Pereira, J.; Prazeres, A.; Mano, R.; Marques, P.; Vargues, A.Rice is one of the most important food crops in the world and the staple for more than half of the global population. Portugal is the first rice consumer, per capita, in Europe and the fourth producer (6 t ha-1), contributing to the 5.3% of the total European production. Rice cultivation in Portugal is intensive and is mostly located in the central and southern regions (Mondego, Tagus and Sado Valleys). The cultivation in Europe is mainly by flooding to control soil temperature, weeds and pests. The water content of soils can vary considerably, depending on climatic conditions, soil type and agricultural practices. In Portugal, rice straw is returned to the field after harvest, partially is burnt and partly is incorporated preceding the rice cultivation. Straw incorporation in soil in the non-rice-growing season can result in lower methane emission in the following rice-growing season than does the incorporation just before rice cultivation. The anaerobic conditions in flooded soils influence nitrogen (N) fertilizers dynamics, particularly the redox potential and soil pH. Rice roots absorb nitrate (NO3 –) or ammonium (NH4 +) from soil using a variety of transporters, but NH4 + is the preferential form in waterlogged soils. Nitrogen use efficiency is generally low (20-35%). In 2011, we evaluated the soil and floodwater N and pH dynamics, and the rice response to the actual agricultural practices in an open field at Salvaterra de Magos (central Portugal), and in open top chambers with increased atmospheric carbon dioxide concentration [CO2] and temperature.
- 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.