Fosfatos nanométricos dispersos em ureia na eficiência agronômica de fósforo em solo oxídico
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Data
2021-07-12
Autores
Reis, Heitor Pontes Gestal [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O fósforo (P) é um importante macronutriente responsável pelo crescimento e produção de culturas agrícolas. Desenvolver práticas eficientes de fertilização tornou-se cada vez mais importante devido à crescente demanda global por alimentos. Cerca de 80-90% de P aplicado como fertilizante é perdido para o ambiente ou ligado quimicamente no solo, portanto não disponível para plantas. Os fertilizantes nanoparticulados apresentam um potencial para melhoraria na eficiência de P, com base na hipótese de que as partículas de tamanho nanométrico apresentam maior mobilidade e disponibilidade no solo. No entanto, um desafio a ser superado é o desenvolvimento de estratégias para manter as partículas de fosfatos em escala nanométricas e evitar sua reaglomeração. Estudos recentes têm demostrado que a ureia fertilizante apresenta potencial como matriz para dispersão de fosfatos minerais, evitando a reaglomeração das partículas, aumentando a solubilidade e alterando a dinâmica do P no solo. Portanto, a proposta central deste trabalho foi processar e caracterizar nanocompósitos baseado na dispersão de hidroxiapatita (HAP) (utilizada como fonte modelo de fosfatos minerais), Bayóvar (BAY) e superfosfato triplo (SFT) em matriz de ureia e avaliar os aspectos agronômicos relacionados a dinâmica do P no solo e suprimento deste nutriente a planta, bem como compreender o sinergismo e a interação entre a ureia e as partículas de fosfato. A preparação do novo fertilizante foi baseada no processo de extrusão, a partir de frações de HAP, BAY e SFT moídas até faixas nanométricas e dispersas em matriz de ureia e amido por este método. Após a síntese foram realizadas as caracterizações dos nanocompósitos, seguidos por experimentos de eficiência agronômica. O primeiro estudo foi realizado com o objetivo de compreender a taxa de liberação e a cinética de liberação do íon fosfato no solo. Para isso foram realizados estudos de bancada visando avaliar a taxa de liberação dos fertilizantes ao longo de uma semana. Em placas de Petri, os grânulos de cada fertilizante foram inseridos no centro da placa e a zona de difusão de P foi avaliada pelo método não destrutivo através da marcação da mesma em papéis de filtro, visando obter uma linha do tempo do caminhamento do P. Ao final foram determinados os teores de P e o pH em diferentes distancias em relação ao centro das placas. Em casa de vegetação foi realizado um experimento em vasos com o objetivo de avaliar a dinâmica do P através do método da extração sequencial, bem como avaliar o crescimento de raízes através do software WinRhizo, além de verificar a capacidade desses materiais em suprir a demanda nutricional do Panicum maximum cv. BRS ‘Zuri’, através da realização de quatro cortes no momento em que as plantas atingiam a altura de corte. Por fim, ainda em casa de vegetação, foi realizado outro experimento utilizando Plant Growth Containers (PGCs) com o objetivo de avaliar a mobilidade de P e a capacidade do mesmo em atingir as raízes das plantas. Para esse estudo foram selecionados os materiais HAP, HAP 2:1, SFT e SFT, sendo aplicados na parte inferior dos PGCs na profundidade de 5,0 cm em dois tipos de sistemas, com planta e sem planta. Os resultados revelaram que a matriz de dispersão foi eficaz em manter as partículas de fosfatos em escala nanométrica, evitando o processo de reaglomeração o que otimizou o processo de liberação do íon fosfato ao longo do tempo. Também foi observado um aumento do pH do solo na região de aplicação dos grânulos dos nanocompósitos, com consequente aumento do teor de P disponível. Os resultados com plantaa revelaram uma maior eficiência de uso do P na forma de compósitos originados do SFT em relação à fonte pura. Também foi evidenciado o grande potencial dessa tecnologia quando observamos os resultados obtidos nos PGCs, sendo que os teores de P resina no solo fertilizado com SFT 2:1 revelou maiores quantidades de P disponíveis para as plantas em relação ao SFT convencional.
Phosphorus (P) is an important macronutrient responsible for the growth and production of agricultural crops. Developing efficient fertilization practices has become increasingly important due to the growing global food demand. About 80-90% of P applied as a fertilizer is lost to the environment or chemically bound to the soil, therefore not available to plants. Nanoparticulate fertilizers have the potential to improve P efficiency, based on the hypothesis that nanometer-sized particles have greater mobility and availability in the soil. However, a challenge to be overcome is strategies development to maintain the phosphate particles on a nanometric scale and prevent their re-agglomeration. Recent studies have shown that fertilizing urea has potential as a matrix for dispersing mineral phosphates, avoiding particles re-agglomeration, increasing solubility and changing P dynamics in the soil. Therefore, the central purpose of this work was to process and characterize nanocomposites based on hydroxyapatite (HAP) (used as a model mineral phosphates source), Bayóvar (BAY) and triple superphosphate (STP) dispersion in urea matrix, and evaluate the agronomic aspects related to P dynamics in the soil and this nutrient supply to the plant, as well as understanding the synergism and the interaction between urea and phosphate particles. New fertilizer preparation was based on the extrusion process, from HAP, BAY and STP fractions, ground to nanometric ranges and dispersed in urea and starch matrix by this method. After the synthesis, the nanocomposites were characterized, followed by agronomic efficiency experiments. The first study was carried out with the objective to understanding the release rate and the phosphate ion release kinetics in soil. For that, bench studies were carried out to evaluate release rate to fertilizers over a week. In Petri dishes, the granules of each fertilizer were inserted in dish center and the P diffusion zone was evaluated by the non-destructive method by marking it on filter papers, in order to obtain a P path timeline. At the end, P levels and pH were determined at different distances from dishes center. In a greenhouse, an experiment was carried out in pots with the objective to evaluating P dynamics, using the sequential extraction method, as well as evaluating the roots growth using the WinRhizo software, in addition to verifying the capacity of these materials to supply Panicum maximum cv. BRS ‘Zuri’ nutritional demand, since four cuts were made at the time the plants reached the cutting height. Finally, also in a greenhouse, another experiment was carried out using Plant Growth Containers (PGCs) in order to assess P mobility and its ability to reach the plant roots. To this study, the materials HAP, HAP 2:1, STP and STP 2:1 were selected, being applied to the PGCs bottom at a 5.0 cm depth in two systems types, with plant and without plant. The results reveal that the dispersion matrix was effective in maintaining the phosphate particles on a nanoscale, avoiding the re-agglomeration process and optimizing the phosphate ion release process over time. An increase in soil pH was also observed in the region of nanocomposite granules application, with a consequent increase in available P content. The plants results reveal a greater P use efficiency in the composites originated from the STP in relation to the original source. It was also clear this technology great potential when we observed the PGCs results, being the P resin levels in the soil fertilized with STP 2: 1 revealed higher P amounts available to the plants in relation to the conventional STP.
Phosphorus (P) is an important macronutrient responsible for the growth and production of agricultural crops. Developing efficient fertilization practices has become increasingly important due to the growing global food demand. About 80-90% of P applied as a fertilizer is lost to the environment or chemically bound to the soil, therefore not available to plants. Nanoparticulate fertilizers have the potential to improve P efficiency, based on the hypothesis that nanometer-sized particles have greater mobility and availability in the soil. However, a challenge to be overcome is strategies development to maintain the phosphate particles on a nanometric scale and prevent their re-agglomeration. Recent studies have shown that fertilizing urea has potential as a matrix for dispersing mineral phosphates, avoiding particles re-agglomeration, increasing solubility and changing P dynamics in the soil. Therefore, the central purpose of this work was to process and characterize nanocomposites based on hydroxyapatite (HAP) (used as a model mineral phosphates source), Bayóvar (BAY) and triple superphosphate (STP) dispersion in urea matrix, and evaluate the agronomic aspects related to P dynamics in the soil and this nutrient supply to the plant, as well as understanding the synergism and the interaction between urea and phosphate particles. New fertilizer preparation was based on the extrusion process, from HAP, BAY and STP fractions, ground to nanometric ranges and dispersed in urea and starch matrix by this method. After the synthesis, the nanocomposites were characterized, followed by agronomic efficiency experiments. The first study was carried out with the objective to understanding the release rate and the phosphate ion release kinetics in soil. For that, bench studies were carried out to evaluate release rate to fertilizers over a week. In Petri dishes, the granules of each fertilizer were inserted in dish center and the P diffusion zone was evaluated by the non-destructive method by marking it on filter papers, in order to obtain a P path timeline. At the end, P levels and pH were determined at different distances from dishes center. In a greenhouse, an experiment was carried out in pots with the objective to evaluating P dynamics, using the sequential extraction method, as well as evaluating the roots growth using the WinRhizo software, in addition to verifying the capacity of these materials to supply Panicum maximum cv. BRS ‘Zuri’ nutritional demand, since four cuts were made at the time the plants reached the cutting height. Finally, also in a greenhouse, another experiment was carried out using Plant Growth Containers (PGCs) in order to assess P mobility and its ability to reach the plant roots. To this study, the materials HAP, HAP 2:1, STP and STP 2:1 were selected, being applied to the PGCs bottom at a 5.0 cm depth in two systems types, with plant and without plant. The results reveal that the dispersion matrix was effective in maintaining the phosphate particles on a nanoscale, avoiding the re-agglomeration process and optimizing the phosphate ion release process over time. An increase in soil pH was also observed in the region of nanocomposite granules application, with a consequent increase in available P content. The plants results reveal a greater P use efficiency in the composites originated from the STP in relation to the original source. It was also clear this technology great potential when we observed the PGCs results, being the P resin levels in the soil fertilized with STP 2: 1 revealed higher P amounts available to the plants in relation to the conventional STP.
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Palavras-chave
Fertilizantes fosfatados, Adubos e fertilizantes, Nanotecnologia, Pastagens, Nanotechnology, Fertilizer industry