Adsorção de fósforo e sua relação com formas de ferro em dez solos do Uruguai

Mehlich-1 soil extract is currently used in Rio Grande do Sul (RS) and Santa Catarina (SC) States, in Brazil, to evaluate soil phosphorus available to plants and Mehlich-1 is sensitive to soil buffering capacity. This limitation is overcome partly by soil separation into buffering classes based on soil clay content. However, soil clay content has some technical and operational limitations, such as the underestimation of soil clay levels in soils under no-till. The aim of this study was to evaluate the remaining phosphorus (P-rem) compared to soil clay content as an index of the buffering capacity in soils of RS. The relationship between P-rem and soil clay content was assessed using 200 soil samples from a wide range of locations across the state. In 20 representative soil types, P-rem, soil clay content, P maximum adsorption capacity, total and pedogenic Fe contents, amount of P 2 O 5 needed to increase soil P in 1 mg kg -1 extracted by Mehlich-1 and -3 methods and P capacity factor were determined. Furthermore, a pot experiment was carried out with plants to determine soil P content extracted by Mehlich-1 and -3 at the maximum technical efficiency (MET) and the maximum absorption efficiency (MEA). Correlation analyses were performed between P-rem and soil clay content and, with the attributes of soils involving the P buffering capacity. The relationship between P-rem and soil clay content was described as a decreasing exponential function; however, the adjustment was not adequate to propose critical levels for P-rem. The P-rem index was superior to soil clay index in practically all relationships with the attributes related to the soil buffering capacity of the soils. In some cases, the indexes were similar; however, P-rem was not lower than the soil clay content in any case. The P-rem is a more reliable index to represent soil buffering capacity than the soil clay content in soils from RS, and P-rem might be used to implement soil classes for Mehlich-1 and Mehlich-3 determinations of soil P.

Section: Relationship Between the Physical And Chemical Properties Ofmentioning

confidence: 99%

Substitution of Clay Content for P-Remaining as an Index of the Phosphorus Buffering Capacity for Soils of Rio Grande do Sul

Rogeri

Gianello

Bortolon

et al. 2016

“…Under conditions of greater water availability, dissolution and remobilization mechanisms of Fe come into action, which include reduction and complexation reactions (Schwertmann, 1991), favoring its greater concentration and leaching in soils with a low level of clay. In a study carried out by Hernández and Meurer (1998) in 10 soils of Uruguay, subject to temporal variations in oxidation-reduction conditions, it was observed that soil with low clay contents (cretaceous sandstones) exhibited lower Fe content, and a correlation was observed between Fe contents and clay contents of the soils. In a study evaluating eight soil samples from the provinces of Antwerp and West-Flanders in Belgium with known micronutrient and heavy metal values, and subjected to the treatments of dry soil, soil at field capacity, and saturated soil, Tack et al (2006) observed that the events of wetting and drying of the soil changed the hydration, oxidation, and crystallinity status of the Fe and Mg oxides of the soil, favoring the release of these elements under wetter environments.…”

Section: Soilmentioning

confidence: 99%

Heavy Metals and Micronutrients in the Soil and Grapevine Under Different Irrigation Strategies

Oliveira

Lima

Salviano

et al. 2015

Soils under natural conditions have heavy metals in variable concentrations and there may be an increase in these elements as a result of the agricultural practices adopted. Transport of heavy metals in soil mainly occurs in forms dissolved in the soil solution or associated with solid particles, water being their main means of transport. In this context, the aim of this study was to evaluate the heavy metal and micronutrient content in the soil and in the grapevine plant and fruit under different irrigation strategies. The experiment was carried out in Petrolina, PE, Brazil. The treatments consisted of three irrigation strategies: full irrigation (FI), regulated deficit irrigation (RDI), and deficit irrigation (DI). During the period of grape maturation, soil samples were collected at the depths of 0-10, 10-20, 20-40, 40-60, and 60-80 cm. In addition, leaves were collected at the time of ripening of the bunches, and berries were collected at harvest. Thus, the heavy metal and micronutrient contents were determined in the soil, leaves, and berries. The heavy metal and micronutrient contents in the soil showed a stochastic pattern in relation to the different irrigation strategies. The different irrigation strategies did not affect the heavy metal and micronutrient contents in the vine leaves, and they were below the contents considered toxic to the plant. In contrast, the greater availability of water in the FI treatment favored a greater Cu content in the grape, which may be a risk to vines, causing instability and turbidity. Thus, adoption of deficit irrigation is recommended so as to avoid compromising the stability of tropical wines of the Brazilian Northeast.

“…Muitos trabalhos na literatura indicaram os óxidos de Fe como os principais participantes na elevada CMAP dos solos (Hernández & Meurer, 1998); todavia, os resultados do presente estudo revelam que a fração argila livre dos óxidos de Fe pode também contribuir de maneira significativa para a adsorção de P (Figura 2). O efeito de cimentação e de recobrimento que os óxidos de Fe e a matéria orgânica exercem sobre os demais componentes da fração argila dos solos pode impedir que eles manifestem sua atividade de superfície (Souza Junior et al, 2007) e do Al presente nas entrecamadas dos minerais de argila do tipo 2:1, que podem adsorver grande quantidade de P (Karathanasis & Shumaker, 2009).…”

Section: Relações Entre a Cmap E Os Atributos Mineralógicos Dos Solosunclassified

“…Isso ocorre em razão da maior densidade de sítios ácidos de Lewis (Novais & Smyth, 1999) na superfície dos coloides. Na fração argila natural, os teores de Fe e Al extraídos por ditionito-citrato-bicarbonato de sódio (Fe d e Al d , teor livre) e oxalato ácido de amônio a pH 3 no escuro (Fe o e Al o , teor pobremente cristalino) são alguns dos atributos mineralógicos que melhor se correlacionam com a CMAP (Hernández & Meurer, 1998). Com muita frequência, a correlação com os teores pobremente cristalinos tem sido maior do que com os teores livres (Hernández & Meurer, 1998).…”

Section: Introductionunclassified

“…Na fração argila natural, os teores de Fe e Al extraídos por ditionito-citrato-bicarbonato de sódio (Fe d e Al d , teor livre) e oxalato ácido de amônio a pH 3 no escuro (Fe o e Al o , teor pobremente cristalino) são alguns dos atributos mineralógicos que melhor se correlacionam com a CMAP (Hernández & Meurer, 1998). Com muita frequência, a correlação com os teores pobremente cristalinos tem sido maior do que com os teores livres (Hernández & Meurer, 1998). É comum a atribuição desse fato à elevada área superficial específica dos óxidos pobremente cristalinos (Sambatti et al, 2002).…”

Section: Introductionunclassified

See 1 more Smart Citation

Capacidade máxima de adsorção de fósforo relacionada a formas de ferro e alumínio em solos subtropicais

Vilar¹,

Costa²,

Hoepers³

et al. 2010