Extração seqüencial de Mn e Zn em solos em função do pH e adição de cama-de-frango

Abstract

RESUMOA disponibilidade de micronutrientes catiônicos e sua distribuição nas frações do solo, são afetadas por diversos atributos, como pH e teor de matéria orgânica do solo. Avaliaram-se a disponibilidade de Mn e Zn por três extratores químicos e o fracionamento desses elementos, por meio de extração seqüencial, em função da variação do pH e da adição de cama-defrango, em amostras da camada superficial (0 a 10 cm) de um Neossolo Litólico distrófico típico e de um Cambissolo Húmico alumínico da região da Serra do Rio Grande do Sul, cultivados com videira. Após redução dos valores de pH do solo, de 6,5 para 3,8, ocorreu aumento nos teores disponíveis de Mn e Zn e nos de Mn e Zn ligados à fração trocável, com diminuição nos teores desses elementos ligados à fração orgânica. A aplicação de doses de cama-de-frango contribuiu para aumentar os teores disponíveis e os ligados à fração trocável. A maior proporção do Mn dos solos estudados esteve ligada à fração orgânica (35%) e à fração residual (30%); para o Zn, a maior proporção foi observada na fração residual (55%). Os teores de Mn e Zn extraídos com DTPA, com CaCl 2 0,01 mol L -1 e com Mehlich III, apresentaram relação linear com os teores dos elementos nas frações trocável e ligada à matéria orgânica. Palavras-chave: disponibilidade, extratores químicos, pH, matéria orgânica do solo Sequential extraction of Mn and Zn as a function of pH and addition of poultry litter ABSTRACT The availability of cationic micronutrients and their distribution in different soil fractions are affected by many soil attributes, such as pH and organic matter (OM) contents. Available Zn and Mn contents, obtained with three extractors, and Zn and Mn fractionation were evaluated in samples from surface layers (0 to 10 cm) of a distrophic Lithic Udorthent and a Typic Haplumbrept, as a function of pH variation and addition of poultry litter. Both soils are cultivated with vines, in Rio Grande do Sul highlands (Serra Gaúcha), Brazil. As the pH decreased from 6.8 to 3.8, Zn and Mn available and exchangeable (by sequential extraction) contents increased. On the other hand, Zn and Mn contents bound to OM fraction decreased. The addition of poultry litter promoted an increase in the contents of both available and exchangeable Zn and Mn. The largest proportion of Mn was bound to OM (35%) and to residual fraction (30%), while the largest amount of Zn was in the residual fraction (55%). Zn and Mn extracted by DTPA, CaCl 2 0.01 mol L -1 , Mehlich III had a linear correlation with the exchangeable and with the OM-bound contents.

Copper and zinc fractionation in biosolid cultivated with Pennisetum purpureum in different periods

“…Nonetheless, although plants release acids into the rhizosphere, the buffering character of the organic matter prevents variations of pH. This characteristic is important because, under lower pH conditions, there might be greater availability of heavy metals to plants (Nachtigall et al, 2009). The results found for pH are satisfactory, because very alkaline biosolids require great caution in their application in the soils, since the soil-biosolid mixture must have at least pH 7.0, as established by the CONAMA Resolution 375 (Brasil, 2006).…”

Zinc, copper and manganese availability in soils treated with alkaline sewage sludge from Paraná state (Brazil)

“…As a result, the availability of the elements can be affected, with their liberation into the soil solution or with retention/precipitation (Berton & Nogueira, 2010). Decreased Zn availability with increasing pH is well known and, according to Nachtigall, Nogueirol and Alleoni (2009), this fact is related to the transition of exchangeable Zn to no-exchangeble forms, resulting in precipitation of insoluble forms, such as oxides and organic complex.…”

“…Thus, decreasing levels of available Mn in these soils is directly linked to increased sensitivity of the element to the pH change Lopes;Santos, 2007). With the increase of the soil pH, the Mn 2+ cationic form is converted into manganic oxides (Hue;May, 2002) or strongly bound to organic matter (Moreira et al, 2016;Nachtigall;Nogueirol;Alleonni, 2009). On the other hand, Matinhos and Telêmaco Borba, who obtained an increase in Mn availability, showed behavior contrary to other soils with similar clay and organic matter content.…”

Chemical Attributes of a Dystrophic Red Latosol of Brazilian Cerrado After Poultry Litter Application Associated to a Urea Inhibitor

“…Comparing the available content of these elements in the control treatment to the soil that received 160 t ha -1 of poultry litter, an increase in availability was observed, of 98; 6,537; 639; 45,726% for Mn, Zn, Na and Cu, respectively (Figure 7). Santos et al (2004) and Nachtigall et al (2009) reported similar results, while Malavolta (1979) proposed the opposite, that pH increases in fact decrease Mn, Zn and Cu availability. The rationale for the results observed herein is that the poultry litter contained 559, 745 and 890 mg kg -1 of Mn, Zn and Cu, respectively (Table 1); thus increases in pH reduced the availability of these elements, while application of high doses suppressed pH effects and increased Mn, Zn and Cu availability.…”