Potassium extraction from the silicate rock Verdete using organic acids

ABSTRACT: Although Brazil is one of the world's leading exporter of agricultural products, the country is highly dependent on the importation of potassic fertilizers. K-bearing silicate rocks are reported as potential solutions to reduce external K dependency. This work evaluated K extraction from silicate Verdete rock, a glauconite-bearing rock containing 10 % of K2O, by solubilization with organic acids. Firstly, Verdete rock was reacted during 3-120 h with solutions of citric or oxalic acid at 2 % (m/v) in Erlenmeyer flasks by shaking. Oxalic acid extracted 6.5 % of K in Verdete, while citric acid extracted 2.3 %. Another experiment was performed to evaluate the effect of various oxalic acid concentrations (2, 4, 6, 8, and 10 %) and differing reaction times (12, 24, 48, and 72 h) on K extraction from Verdete rock. Soluble K concentration nearly doubled with the increase of reaction time from 12 to 72 h, rising from 20 to 37 mg L1. Increments in K extraction were obtained by increasing oxalic acid concentrations up to 6 % and above this concentration, no significant gain was observed. The X-ray diffraction data showed that K extraction resulted from the formation of oxalate-metal complexes with metals in Verdete rock.

Potassium extraction from the silicate rock Verdete using organic acids

Although Brazil is one of the world’s leading exporter of agricultural products, the country is highly dependent on the importation of potassic fertilizers. K-bearing silicate rocks are reported as potential solutions to reduce external K dependency. This work evaluated K extraction from silicate Verdete rock, a glauconite-bearing rock containing 10 % of K2O, by solubilization with organic acids. Firstly, Verdete rock was reacted during 3-120 h with solutions of citric or oxalic acid at 2 % (m/v) in Erlenmeyer flasks by shaking. Oxalic acid extracted 6.5 % of K in Verdete, while citric acid extracted 2.3 %. Another experiment was performed to evaluate the effect of various oxalic acid concentrations (2, 4, 6, 8, and 10 %) and differing reaction times (12, 24, 48, and 72 h) on K extraction from Verdete rock. Soluble K concentration nearly doubled with the increase of reaction time from 12 to 72 h, rising from 20 to 37 mg L–¹. Increments in K extraction were obtained by increasing oxalic acid concentrations up to 6 % and above this concentration, no significant gain was observed. The X-ray diffraction data showed that K extraction resulted from the formation of oxalate-metal complexes with metals in Verdete rock.

Potassium extraction from the silicate rock Verdete using organic acids

Although Brazil is one of the world's leading exporter of agricultural products, the country is highly dependent on the importation of potassic fertilizers. K-bearing silicate rocks are reported as potential solutions to reduce external K dependency. This work evaluated K extraction from silicate Verdete rock, a glauconite-bearing rock containing 10 % of K2O, by solubilization with organic acids. Firstly, Verdete rock was reacted during 3-120 h with solutions of citric or oxalic acid at 2 % (m/v) in Erlenmeyer flasks by shaking. Oxalic acid extracted 6.5 % of K in Verdete, while citric acid extracted 2.3 %. Another experiment was performed to evaluate the effect of various oxalic acid concentrations (2, 4, 6, 8, and 10 %) and differing reaction times (12, 24, 48, and 72 h) on K extraction from Verdete rock. Soluble K concentration nearly doubled with the increase of reaction time from 12 to 72 h, rising from 20 to 37 mg L-1. Increments in K extraction were obtained by increasing oxalic acid concentrations up to 6 % and above this concentration, no significant gain was observed. The X-ray diffraction data showed that K extraction resulted from the formation of oxalate-metal complexes with metals in Verdete rock.

Potencial de olivina melilitito, granito e sienito na disponibilização de potássio em solos / Potential of olivine melilitite, granite and sienite in the availability of potassium in soils

O objetivo deste trabalho foi avaliar o potencial de pós de rochas na disponibilização de potássio em solos. O experimento foi conduzido em casa de vegetação utilizando as rochas olivina melilitito, granito e sienito. Amostras de um Cambissolo Húmico e de um Argissolo Vermelho-Amarelo foram coletadas, secas ao ar e peneiradas, corrigidas a pH 5,2 com calcário dolomítico e mantidas a 80% da capacidade de campo na incubação. O experimento foi conduzido em delineamento experimental inteiramente casualizado, com dois solos e cinco formas de K, com quatro repetições por tratamento. Os tratamentos foram os seguintes: sem adubação; KCl, pó de rocha de olivina melilitito e granito e sienito. Os pós de rocha foram acrescentados em quantidades equivalentes a 500 kg ha-1 de K2O, com base no teor total de K das rochas. Após o período de incubação de 180 dias, foram cultivados em sucessão feijão, trigo e trigo mourisco. A determinação do K no solo foi realizada após extração com solução de Mehlich-1 e resina trocadora de íons. O olivina melilitito não diferiu do KCl em relação à absorção de potássio pelas plantas e na disponibilização desse elemento no solo, exceto na extração pela resina no Argissolo após o cultivo de feijão, representando uma fonte potencial deste nutriente a ser melhor avaliada como fertilizante na agricultura. Os pós de rocha de granito e sienito não mostraram resposta quanto às variáveis testadas, evidenciando serem materiais de disponibilização mais lenta de potássio às plantas.

This study aimed to assess the potential of rock powders in the availability of potassium in soils. The experiment was conducted under greenhouse conditions using the rocks olivine melilitite, granite and sienite. Samples of a Humic Cambisol and a Red-Yellow Argisol were collected, air dried and sieved, adjusted to pH 5.2 with lime and incubated at 80% of water fi eld capacity. The experiment was conducted in a completely randomized design using a 2 x 5 factorial, with two soil types and fi ve forms of K, with four replicates. The treatment no fertilizers, KCl, olivine melilitite, and granite and sienite rock powders. Rock powders were added in amounts equivalent to 500 kg ha-1 K2O based on the total K content of the rocks. After an incubation period of 180 days, beans, wheat and buckwheat were grown in succession. The content of K in the soil was determined after extraction with Mehlich-1 and ion exchange resin. Olivine melilitite did not differ from KCl in relation to potassium uptake by plants and in the availability of K in the soil, except for resin extraction in Argisol after beans cultivation, so it represents a potential K source to be better evaluated as agricultural fertilizer.The granite and sienite powder did not respond to the variables tested, which points out that they are materials with slow K availability to plants.

Potencial de olivina melilitito, granito e sienito na disponibilização de potássio em solos / Potential of olivine melilitite, granite and sienite in the availability of potassium in soils

O objetivo deste trabalho foi avaliar o potencial de pós de rochas na disponibilização de potássio em solos. O experimento foi conduzido em casa de vegetação utilizando as rochas olivina melilitito, granito e sienito. Amostras de um Cambissolo Húmico e de um Argissolo Vermelho-Amarelo foram coletadas, secas ao ar e peneiradas, corrigidas a pH 5,2 com calcário dolomítico e mantidas a 80% da capacidade de campo na incubação. O experimento foi conduzido em delineamento experimental inteiramente casualizado, com dois solos e cinco formas de K, com quatro repetições por tratamento. Os tratamentos foram os seguintes: sem adubação; KCl, pó de rocha de olivina melilitito e granito e sienito. Os pós de rocha foram acrescentados em quantidades equivalentes a 500 kg ha-1 de K2O, com base no teor total de K das rochas. Após o período de incubação de 180 dias, foram cultivados em sucessão feijão, trigo e trigo mourisco. A determinação do K no solo foi realizada após extração com solução de Mehlich-1 e resina trocadora de íons. O olivina melilitito não diferiu do KCl em relação à absorção de potássio pelas plantas e na disponibilização desse elemento no solo, exceto na extração pela resina no Argissolo após o cultivo de feijão, representando uma fonte potencial deste nutriente a ser melhor avaliada como fertilizante na agricultura. Os pós de rocha de granito e sienito não mostraram resposta quanto às variáveis testadas, evidenciando serem materiais de disponibilização mais lenta de potássio às plantas.(AU)

This study aimed to assess the potential of rock powders in the availability of potassium in soils. The experiment was conducted under greenhouse conditions using the rocks olivine melilitite, granite and sienite. Samples of a Humic Cambisol and a Red-Yellow Argisol were collected, air dried and sieved, adjusted to pH 5.2 with lime and incubated at 80% of water fi eld capacity. The experiment was conducted in a completely randomized design using a 2 x 5 factorial, with two soil types and fi ve forms of K, with four replicates. The treatment no fertilizers, KCl, olivine melilitite, and granite and sienite rock powders. Rock powders were added in amounts equivalent to 500 kg ha-1 K2O based on the total K content of the rocks. After an incubation period of 180 days, beans, wheat and buckwheat were grown in succession. The content of K in the soil was determined after extraction with Mehlich-1 and ion exchange resin. Olivine melilitite did not differ from KCl in relation to potassium uptake by plants and in the availability of K in the soil, except for resin extraction in Argisol after beans cultivation, so it represents a potential K source to be better evaluated as agricultural fertilizer.The granite and sienite powder did not respond to the variables tested, which points out that they are materials with slow K availability to plants.(AU)