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Avaliação agronómica de fertilizantes azotados de base biológica
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Abstract(s)
Os adubos minerais azotados são os fertilizantes mais consumidos na fertilização das culturas agrícolas na União Europeia. No entanto, os efluentes da produção pecuária contêm azoto, tanto orgânico como inorgânico, constituindo uma fonte deste nutriente para as culturas. Atualmente, têm-se desenvolvido tecnologias para remoção e captura de azoto destes efluentes, obtendo-se fertilizantes azotados minerais que permitem realizar adubações mais racionais e minimizam perdas para cursos de água ou para a atmosfera, comparativamente à aplicação direta dos efluentes pecuários. A recuperação de nutrientes destes efluentes enquadra-se no princípio da economia circular e na utilização sustentável dos recursos. A tecnologia de membranas permeáveis aos gases é um dos processos mais eficientes nessa recuperação de azoto, obtendo-se um fertilizante líquido com uma concentração conhecida de azoto na forma de sulfato de amónio.
O objetivo deste trabalho foi avaliar o valor agronómico de duas soluções azotadas obtidas por recuperação de azoto de dois efluentes distintos através do processo de membranas permeáveis aos gases, comparando-as com a adubação azotada tradicional. Os efluentes utilizados foram: digestato obtido após digestão anaeróbia de efluente pecuário (S-DS) e digestato obtido após codigestão anaeróbia de efluente de indústria agroalimentar e de matadouro (S-DAM). O valor agronómico das soluções obtidas foi avaliado numa cultura de outono-inverno, o triticale (×Triticosecale Wittm., var. Misionero), e numa cultura hortícola, a alface (Lactuca sativa L., var. Grand Rapids), realizada na primavera-verão.
Para atender ao objetivo proposto, realizaram-se dois ensaios em vaso. O primeiro decorreu no Centro de Ensaios da Escola Superior Agrária de Castelo Branco utilizando o triticale, e o segundo no Centro de Biotecnologia de Plantas da Beira Interior com a alface, ambos cultivados num solo de textura ligeira, um Regossolo (IUSS Working Group WRB, 2015). O delineamento experimental adotado foi completamente casualizado, com cinco modalidades e três repetições por modalidade em cada ensaio. No ensaio da alface, cada repetição incluiu dois vasos. Além das modalidades S-DS e S-DAM, testaram-se a testemunha (T, sem adubação) e duas modalidades com fertilização azotada tradicional, uma com adubo mineral comercial (F-N) e outra com adubação mineral azotada em solução (S-N). O quantitativo de azoto aplicado por vaso foi igual em todas as modalidades, exceto na testemunha, correspondendo a 170 kg N/ha no triticale e 65 kg N/ha na alface.
Os resultados evidenciaram diferenças no comportamento agronómico entre as soluções de azoto recuperado. A solução S-DAM apresentou desempenho agronómico, produção de biomassa e eficiência na utilização do azoto semelhantes aos da fertilização tradicional no triticale, e significativamente superiores na alface. A solução S-DS originou um comportamento agronómico similar à fertilização tradicional em ambas as culturas. Uma vez que a composição físico-química das duas soluções era similar, os resultados sugerem a presença de compostos orgânicos distintos, com potencial bioestimulante na solução S-DAM e, eventualmente, inibidor na S-DS. Embora as soluções com azoto recuperado tenham demonstrado potencial como fertilizantes, recomenda-se a sua caracterização em termos de compostos orgânicos, de forma a otimizar a sua utilização agronómica.
Abstract: Nitrogen mineral fertilizers are the most widely used fertilizers in the European Union. However, livestock production effluents contain nitrogen in both organic and inorganic forms, representing a potential source of this nutrient for crops. In recent years, technologies have been developed to remove and capture nitrogen from these effluents, allowing the production of nitrogen mineral fertilizers that enable a more efficient fertilization while reducing nitrogen losses to watercourses and to the atmosphere compared to the direct application of livestock effluents. The recovery of nutrients from these effluents aligns with the principles of the circular economy and the sustainable use of resources. Gas-permeable membrane technology is one of the most efficient processes for nitrogen recovery, yielding a liquid fertilizer with a known nitrogen concentration in the form of ammonium sulfate. This study aimed to evaluate the agronomic value of two nitrogen solutions obtained through nitrogen recovery from two distinct effluents using gas-permeable membrane technology, comparing them with conventional nitrogen fertilization. The effluents used were: digestate obtained after anaerobic digestion of livestock effluent (S-DS) and digestate obtained after anaerobic co-digestion of agro-industrial and slaughterhouse effluents (S-DAM). The agronomic value of recovered nitrogen solutions was assessed in an autumn-winter crop, triticale (×Triticosecale Wittm., var. Misionero), and in a spring-summer horticultural crop, lettuce (Lactuca sativa L., var. Grand Rapids). To achieve this objective, two pot experiments were conducted. The first was carried out at the Experimental Center of the Agriculture School of Castelo Branco using triticale, while the second took place at the Plant Biotechnology Center of Beira Interior with lettuce. Both crops were grown in a light textured soil classified as a Regosol (IUSS Working Group WRB, 2015). The experimental design was completely randomized, with five treatments and three replicates per treatment in each experiment. In the lettuce experiment, each replicate included two pots. In addition to the S-DS and S-DAM treatments, a control treatment (T, without fertilization) and two treatments with traditional nitrogen fertilization were tested: one with a commercial mineral fertilizer (F-N) and the other with a solution of a nitrogen mineral fertilizer (S-N). The amount of nitrogen applied per pot was the same across all treatments, except for the control, corresponding to 170 kg N/ha in triticale and 65 kg N/ha in lettuce. The results highlighted differences in the agronomic performance of the recovered nitrogen solutions. The S-DAM solution exhibited agronomic performance, biomass production, and nitrogen use efficiency comparable to conventional fertilization in triticale and with significantly superior results in lettuce. The S-DS solution showed agronomic performance similar to conventional fertilization in both crops. Considering that the physicochemical composition of both nitrogen solutions was similar, the results suggest the presence of distinct organic compounds, with potential bio-stimulant effects in S-DAM and possibly inhibitory effects in S-DS. Although the recovered nitrogen solutions demonstrated potential as fertilizers, further characterization of their organic compounds is recommended to optimize their agronomic use.
Abstract: Nitrogen mineral fertilizers are the most widely used fertilizers in the European Union. However, livestock production effluents contain nitrogen in both organic and inorganic forms, representing a potential source of this nutrient for crops. In recent years, technologies have been developed to remove and capture nitrogen from these effluents, allowing the production of nitrogen mineral fertilizers that enable a more efficient fertilization while reducing nitrogen losses to watercourses and to the atmosphere compared to the direct application of livestock effluents. The recovery of nutrients from these effluents aligns with the principles of the circular economy and the sustainable use of resources. Gas-permeable membrane technology is one of the most efficient processes for nitrogen recovery, yielding a liquid fertilizer with a known nitrogen concentration in the form of ammonium sulfate. This study aimed to evaluate the agronomic value of two nitrogen solutions obtained through nitrogen recovery from two distinct effluents using gas-permeable membrane technology, comparing them with conventional nitrogen fertilization. The effluents used were: digestate obtained after anaerobic digestion of livestock effluent (S-DS) and digestate obtained after anaerobic co-digestion of agro-industrial and slaughterhouse effluents (S-DAM). The agronomic value of recovered nitrogen solutions was assessed in an autumn-winter crop, triticale (×Triticosecale Wittm., var. Misionero), and in a spring-summer horticultural crop, lettuce (Lactuca sativa L., var. Grand Rapids). To achieve this objective, two pot experiments were conducted. The first was carried out at the Experimental Center of the Agriculture School of Castelo Branco using triticale, while the second took place at the Plant Biotechnology Center of Beira Interior with lettuce. Both crops were grown in a light textured soil classified as a Regosol (IUSS Working Group WRB, 2015). The experimental design was completely randomized, with five treatments and three replicates per treatment in each experiment. In the lettuce experiment, each replicate included two pots. In addition to the S-DS and S-DAM treatments, a control treatment (T, without fertilization) and two treatments with traditional nitrogen fertilization were tested: one with a commercial mineral fertilizer (F-N) and the other with a solution of a nitrogen mineral fertilizer (S-N). The amount of nitrogen applied per pot was the same across all treatments, except for the control, corresponding to 170 kg N/ha in triticale and 65 kg N/ha in lettuce. The results highlighted differences in the agronomic performance of the recovered nitrogen solutions. The S-DAM solution exhibited agronomic performance, biomass production, and nitrogen use efficiency comparable to conventional fertilization in triticale and with significantly superior results in lettuce. The S-DS solution showed agronomic performance similar to conventional fertilization in both crops. Considering that the physicochemical composition of both nitrogen solutions was similar, the results suggest the presence of distinct organic compounds, with potential bio-stimulant effects in S-DAM and possibly inhibitory effects in S-DS. Although the recovered nitrogen solutions demonstrated potential as fertilizers, further characterization of their organic compounds is recommended to optimize their agronomic use.
Description
Trabalho de Projeto apresentado à Escola Superior Agrária de Castelo Branco do Instituto Politécnico de Castelo Branco para cumprimento dos requisitos necessários à obtenção do grau de Mestre em Engenharia Agronómica.
Keywords
Economia circular Sustentabilidade da fertilização Membranas permeáveis aos gases Recuperação de azoto Eficiência agronómica do azoto Circular economy Sustainable fertilization Gas-permeable membranes Nitrogen recovery Agronomic nitrogen efficiency