Extractants to assess zinc phytoavailability in mineral fertilizer and industrial by-products

Abstract

SUMMARYEfficient analytical methods for the quantification of plant-available Zn contained in mineral fertilizers and industrial by-products are fundamental for the control and marketing of these inputs. In this sense, there are some doubts on the part of the scientific community as well as of the fertilizer production sector, whether the extractor requested by the government (Normative Instruction No. 28, called 2 nd extractor), which is citric acid 2 % (2 % CA) (Brasil, 2007b), is effective in predicting the plant availability of Zn via mineral fertilizers and about the agronomic significance of the required minimal solubility of 60 % compared to the total content (HCl) (Brasil, 2007a). The purpose of this study was to evaluate the alternative extractors DTPA, EDTA, neutral ammonium citrate (NAC), buffer solution pH 6.0, 10 % HCl, 10 % sulfuric acid, 1 % acetic acid, water, and hot water to quantify the contents of Zn available for maize and compare them with indices of agronomic efficiency of fertilizers and industrial by-products when applied to dystrophic Clayey Red Latosol and Dystrophic Alic Red Yellow Latosol with medium texture. The rate of Zn applied to the soil was 5 mg kg -1 , using the sources zinc sulfate, commercial granular zinc, ash and galvanic sludge, ash and two brass slags. Most Zn was extracted from the sources by DTPA, 10 % HCl, NAC, 1% acetic acid, and 10 % sulfuric acid. Recovery by the extractors 2 % CA, EDTA, water, and hot water was low. The agronomic efficiency index was found to be high when using galvanic sludge (238 %) and commercial granular zinc (142 %) and lower with brass slag I and II (67 and 27 %, respectively). The sources galvanizing ash and brass ash showed solubility lower than 60 % in 2 % CA, despite agronomic efficiency indices of 78 and 125 %, respectively. The low agronomic efficiency index of (Brasil, 2007b) RESUMO: EXTRATORES PARA AVALIAÇÃO DA FITODISPONIBILIDADE DE ZINCO EM FERTILIZANTES MINERAIS E MATERIAIS SECUNDÁRIOS A utilização de métodos analíticos eficientes na quantificação do Zn fitodisponível contido em fertilizantes minerais e materiais secundários é fundamental no controle e na comercialização desses insumos. Nesse sentido, há dúvidas no setor científico e no de produção de fertilizantes se o extrator exigido na Instrução Normativa nº 28, ácido cítrico 2 % (AC 2 %)

Comparison and modelling of extraction methods to assess agronomic effectiveness of fertilizer zinc

“…Even though total Zn is not a good indicator of Zn availability in fertilizer, this is usually the only information given on fertilizer labels, technical data sheets, and fertilizer manufacturer websites. In most countries, there are no requirements regarding “available Zn”, though in Brazil, the fertilizer legislation regulates that Zn fertilizers should contain at least 60% of Zn in citrate acid‐extractable form ( Montalvo et al., ), but the scientific basis of this directive has been questioned ( Souza et al., ). Several scientific studies have used water‐extractable Zn as an indicator of plant availability, using various procedures ( Richards , ; Amrani et al., ; Liscano et al., ).…”

Phytoavailability of Copper in Industrial by-Products and Mineral Fertilizers

“…The extractants tested for their ability to extract Cu from sources were neutral ammonium citrate+water 1:1 and 2 % citric acid, both methods according to Brasil (2007b); 10 % H 2 SO 4 (Bastos et al, 2007b); 10 % HCl (Souza et al, 2013); 1 % acetic acid (Gallo, 1954); 0.24 mol L -1 buffer solution Bis (hydroxymethyl) -2,2,2"-nitrilotriethanol (C 8 H 19 NO 5 ) pH 6.0 (FDACS, 2013); 50 mmol L -1 diethylenetriaminepentaacetic acid (DTPA) (modified from Vale and Alcarde, 1999); 5 mmol L -1 ethylenediaminetetraacetic acid (EDTA); water, as described by Vale and Alcarde (1999); and hot water (AOAC, 1997). The total Cu content was assessed by 37 % heat-concentrated HCl (hot plate), the official method of MAPA (Brasil, 2007b).…”

“…Analytical quantification was performed using the technique of inductively coupled plasma with optical emission spectrometry (ICP-OES). The details of the methods were described by Souza et al (2013).…”

Comparison of Analytical Methods for Quantifying the Levels of Lead, Cadmium, Chromium, and Nickel in Mineral Fertilizers and Industrial By-products

“…The methods evaluated were USEPA 3051a (USEPA 2008), concentrated HCl (Brazil 2007c), 10 percent HCl (Souza et al 2013), 10 percent sulfuric acid (H 2 SO 4 ) (Bastos et al 2007), and 50 mmol L −1 diethylenetriaminepentaacetic acid (DTPA) (modified from Vale and Alcarde 1999). The details of the methodologies were described by Souza et al (2013).…”