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Abstract(s)
O azoto é um nutriente essencial para o desenvolvimento das plantas, sendo muitas vezes limitada a sua disponibilidade em sistemas de cultivo. Por este motivo, a adição de azoto em forma de fertilizante é comum na agricultura. Elevadas aplicações de azoto no solo, associadas com a sua elevada mobilidade no sistema solo-planta-atmosfera, podem resultar em diversos prejuízos econômicos, na saúde humana, animal e no meio ambiente. Neste sentido, o biochar e zeólitos são condicionadores que estão sendo estudados, tendo em vista controlar a disponibilidade deste nutriente no solo. Neste contexto, o objetivo deste estudo foi avaliar o efeito da aplicação de biochar e zeólitos na disponibilidade de azoto aplicado na forma de ureia para as plantas. Os tratamentos utilizados foram: Solo (S), Solo + Ureia (SU), Solo + Ureia + Biochar (SUB), Solo + Ureia + Zeólitos (SUZ) e Solo + Ureia + Biochar + Zeólitos (SUBZ), aplicados em 3 ensaios distintos: dois com plantas teste (alface e azevém), e o terceiro sem plantas em que se acompanhou a evolução de nitratos e fosfatos no solo recorrendo a resinas de troca aniônica. Foram feitas 4 repetições de cada tratamento em cada ensaio. Os ensaios decorreram nas estufas do Instituto Politécnico de Bragança em vasos com 3 kg de solo. Todos levaram uma adubação de base com macro e micronutrientes. À exceção do tratamento S, a quantidade de azoto aplicado em cada vaso foi de 360 mg, fracionado 2 vezes. A quantidade de biochar e zeólitos foi de 20 gramas por vaso. Fizeram-se dois ciclos de alface e 4 cortes no azevém. Nas plantas (azevém e alface) avaliou-se a produção de matéria seca, concentração de nutrientes, eficiência de uso de N. No solo das alfaces, avaliou-se, no fim do segundo ciclo, o teor de nutrientes, pH e matéria orgânica. Nas resinas de troca aniônica avaliou-se a concentração de nitratos e fosfatos. Os dados foram submetidos à análise de comparação múltipla de médias de Tukey (α = 0,05%). A produção de biomassa diferiu em cada um dos ensaios. Nos dois ciclos de alface não se verificaram diferenças significativas na produção de biomassa nos diferentes tratamentos. No azevém a produção foi significativamente superior nos tratamentos com condicionadores, especialmente com zeólitos. A aplicação de zeólitos contribuiu para o aumento da concentração de potássio nos tecidos vegetais. No solo a aplicação de biochar aumentou o teor de matéria orgânica e a aplicação de zeólitos aumentou a concentração de potássio. Ambos os condicionadores aumentaram a capacidade de troca catiónica, mas o efeito não foi muito significativo dada a natureza do solo usado no ensaio, com valores adequados para este parâmetro. No ensaio com resinas constatou-se a menor disponibilidade de nitratos e fosfatos nos solos com os condicionadores. Os zeólitos tiveram efeito mais marcado na redução da disponibilidade de fosfatos. Os resultados apontam para uma maior eficiência dos zeólitos no controle de nutrientes no solo, mas esse controle pode estar associado à natureza do ião. A resposta das culturas à aplicação dos condicionadores parece depender da espécie e do tempo em que permanecem no solo.
Nitrogen is an essential nutrient for the development of plants, and their availability in cropping systems is often limited. For this reason, the addition of nitrogen as fertilizer is common in agriculture. High nitrogen applications in the soil, associated with its high mobility in the soil-plant-atmosphere system, can result in several economic, in human, animal and environmental health damages. In this sense, the biochar and zeolites are conditioners that are being studied, in order to control the availability of nitrogen in the soil. In this context, the objective of this study was to evaluate the effect of the application of biochar and zeolites on the availability of nitrogen applied in the form of urea to the plants. The treatments used were: Soil (S), Soil + Urea (SU), Soil + Urea + Biochar (SUB), Soil + Urea + Zeolites (SUZ) and Soil + Urea + Biochar + Zeolites applied in three distinct treatments: two of them with test plants (lettuce and ryegrass), and the third without plants in which the evolution of nitrates and phosphates in the soil was monitored using anion exchange resins. Four replicates of each treatment were made in each assay. The experiments were carried out in the greenhouses of the Polytechnic Institute of Bragança in pots with 3 kg of soil. All of them took a basic fertilization with macro and micronutrients. Except for the S treatment, the amount of nitrogen applied in each pot was 360 mg, fractionated in 2 times. The amount of biochar and zeolites was 20 grams per pot. There were two cycles of lettuce and four cuts of ryegrass. In the plants (ryegrass and lettuce) the dry matter production, nutrient concentration, N use efficiency were evaluated. At the end of the second cycle, the nutrient, pH and organic matter content were evaluated. In the anion exchange resins, the concentration of nitrates and phosphates was evaluated. The data were submitted to the Tukey averages multiple comparison (α = 0.05%). Biomass production differed in each of the trials. In both lettuce cycles there were no significant differences in biomass production in the different treatments. In ryegrass, production was significantly higher in treatments with conditioners, especially with zeolites. The application of zeolites contributed to the increase of potassium concentration in plant tissues. In the soil, the biochar application increased the organic matter content and the zeolite application increased the potassium concentration. Both conditioners increased the cation exchange capacity, but the effect was not very significant due to the nature of the soil used in the test, with values suitable for this parameter. In the resin test, a lowest availability of nitrates and phosphates in soils with the conditioners was observed. The presence of zeolites resulted on reducing the availability of phosphates. The results indicate a higher efficiency of the zeolites in soil nutrient control, but it may be related to the nature of the ion. The behaviour of the plants to the application of conditioners seems to depend on the species and on the time they remain in the soil.
Nitrogen is an essential nutrient for the development of plants, and their availability in cropping systems is often limited. For this reason, the addition of nitrogen as fertilizer is common in agriculture. High nitrogen applications in the soil, associated with its high mobility in the soil-plant-atmosphere system, can result in several economic, in human, animal and environmental health damages. In this sense, the biochar and zeolites are conditioners that are being studied, in order to control the availability of nitrogen in the soil. In this context, the objective of this study was to evaluate the effect of the application of biochar and zeolites on the availability of nitrogen applied in the form of urea to the plants. The treatments used were: Soil (S), Soil + Urea (SU), Soil + Urea + Biochar (SUB), Soil + Urea + Zeolites (SUZ) and Soil + Urea + Biochar + Zeolites applied in three distinct treatments: two of them with test plants (lettuce and ryegrass), and the third without plants in which the evolution of nitrates and phosphates in the soil was monitored using anion exchange resins. Four replicates of each treatment were made in each assay. The experiments were carried out in the greenhouses of the Polytechnic Institute of Bragança in pots with 3 kg of soil. All of them took a basic fertilization with macro and micronutrients. Except for the S treatment, the amount of nitrogen applied in each pot was 360 mg, fractionated in 2 times. The amount of biochar and zeolites was 20 grams per pot. There were two cycles of lettuce and four cuts of ryegrass. In the plants (ryegrass and lettuce) the dry matter production, nutrient concentration, N use efficiency were evaluated. At the end of the second cycle, the nutrient, pH and organic matter content were evaluated. In the anion exchange resins, the concentration of nitrates and phosphates was evaluated. The data were submitted to the Tukey averages multiple comparison (α = 0.05%). Biomass production differed in each of the trials. In both lettuce cycles there were no significant differences in biomass production in the different treatments. In ryegrass, production was significantly higher in treatments with conditioners, especially with zeolites. The application of zeolites contributed to the increase of potassium concentration in plant tissues. In the soil, the biochar application increased the organic matter content and the zeolite application increased the potassium concentration. Both conditioners increased the cation exchange capacity, but the effect was not very significant due to the nature of the soil used in the test, with values suitable for this parameter. In the resin test, a lowest availability of nitrates and phosphates in soils with the conditioners was observed. The presence of zeolites resulted on reducing the availability of phosphates. The results indicate a higher efficiency of the zeolites in soil nutrient control, but it may be related to the nature of the ion. The behaviour of the plants to the application of conditioners seems to depend on the species and on the time they remain in the soil.
Description
Keywords
Condicionadores do solo Análise foliar Análise do solo Membrana de troca aniônica