Abstract:Os solos de várzea, sazonalmente alagados para o cultivo do arroz, apresentam alternância nas condições de oxidação e redução, que determinam modificações intensas na fase sólida mineral do solo e na dinâmica de elementos reativos, como o fósforo. Este estudo teve como objetivo avaliar o efeito da drenagem de dois solos de várzea, (Planossolo Háplico e Chernossolo Ebânico), após período de alagamento sobre a capacidade máxima de adsorção de fósforo (CMAP). O experimento foi conduzido em casa de vegetação, o fa… Show more
“…With these oxidation-reduction reactions, the pH values are changed, increasing the availability of elements like Fe and Mn (Ponnamperuma 1972). Phosphorus has its dynamics modified due to adsorption on the surface of these oxides, and can be released in the soil solution (Teixeira et al 2018). However, this released concentration was not sufficient to observe high levels in the standing water.…”
The objective of this paper was to evaluate the quality of water drained after the use of the knife-roller (an implement used to incorporate rice residues after harvest), the partial global warming potential (pGWP) and straw decomposition as a result of postharvest field management of irrigated rice. The experiments were conducted during the 2018 and 2019 offseason and the treatments consisted of several water drainage periods (0, 3, 6, 9 and 12 days) after a field pass with a knife-roller. In addition, a nonflooded harvest treatment without straw management was included. Analysis of drainage water three days after a pass with the kniferoller showed a reduction in total soluble solids by 94% compared to zero days. Nitrogen and soluble phosphorus were not influenced by the treatments. However, potassium levels increased as the drainage period increased, which is related to the period between harvest and drainage. As the electrical conductivity is influenced by the concentration of ions, it showed the same response curve as the potassium levels and, for pH, there were small oscillations influenced by the temperature. The total CH 4 emission and the pGWP were higher when the water depth remained for a longer period. However, the N 2 O emissions were higher in the absence of soil submersion. Water should be drained three days after a pass with the knife-roller in order to reduce potassium loss and suspended solids as well as pGWP. The use of the knife-roller accelerated the process of straw decomposition in relation to the unmanaged straw treatment.
“…With these oxidation-reduction reactions, the pH values are changed, increasing the availability of elements like Fe and Mn (Ponnamperuma 1972). Phosphorus has its dynamics modified due to adsorption on the surface of these oxides, and can be released in the soil solution (Teixeira et al 2018). However, this released concentration was not sufficient to observe high levels in the standing water.…”
The objective of this paper was to evaluate the quality of water drained after the use of the knife-roller (an implement used to incorporate rice residues after harvest), the partial global warming potential (pGWP) and straw decomposition as a result of postharvest field management of irrigated rice. The experiments were conducted during the 2018 and 2019 offseason and the treatments consisted of several water drainage periods (0, 3, 6, 9 and 12 days) after a field pass with a knife-roller. In addition, a nonflooded harvest treatment without straw management was included. Analysis of drainage water three days after a pass with the kniferoller showed a reduction in total soluble solids by 94% compared to zero days. Nitrogen and soluble phosphorus were not influenced by the treatments. However, potassium levels increased as the drainage period increased, which is related to the period between harvest and drainage. As the electrical conductivity is influenced by the concentration of ions, it showed the same response curve as the potassium levels and, for pH, there were small oscillations influenced by the temperature. The total CH 4 emission and the pGWP were higher when the water depth remained for a longer period. However, the N 2 O emissions were higher in the absence of soil submersion. Water should be drained three days after a pass with the knife-roller in order to reduce potassium loss and suspended solids as well as pGWP. The use of the knife-roller accelerated the process of straw decomposition in relation to the unmanaged straw treatment.
“…The factors that influence the adsorption and availability of P can vary horizontally, according to the soil class, by specific formation processes, such as plinting and gleisation and can vary vertically in the soil profile, according to the layer compositions (Teixeira et al, 2018). Among the factors that can determine the behavior of P in the soil profile are the amount of organic matter, clay, pH and the levels and types of Fe and Al oxides.…”
Amazonian soils have some physical, chemical and mineralogical differences, understanding the differences is important to understand the behavior of nutrients in the soil, especially phosphorus. The study was carried out in two types of soils: a Hydromorphic soil profile and a Non-hydromorphic soil profile in the Central Amazon region of Brazil, located in the metropolitan area of Manaus. Five depths were sampled: 0.00-0.05; 0.05-0.1; 0.1-0.2; 0.2-0.4; and 0.4-0.6 m. Physical, chemical, mineralogical and morphological attributes of both soils were studied. With the exception of clay, the levels of sand and silt remained stable in depth. The levels of organic matter gradually decrease in depth. The pH in water and in KCl, ∆pH, point of zero load, were similar between the surface and subsurface soils. Al 3+ , H + +Al 3+ , CECt, CECT and clay activity were similar in Non-hydromorphic soil and increase in surface (< 0.2 m) and stabilize in subsurface (> 0.2 m). In both soils, the bases are reduced in subsurface (> 0.2 m). Aluminum and iron oxalate reduce with greater expressiveness in Non-hydromorphic soil. Aluminum and dithionite iron exhibit the same behavior. The levels of Goethite (Gt) and Hematite (Hm) are high in depth in the Non-hydromorphic soil and decrease in the Hydromorphic soil. There are sensitive distinctions between soils, due to the imposed edaphoclimatic conditions.
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