Resumo -O objetivo deste trabalho foi calibrar uma câmara prática e de baixo custo, para quantifi car a amônia volatilizada do solo. A calibração da câmara foi realizada pela técnica do balanço do isótopo 15 N. A amônia volatilizada foi capturada por uma câmara semiaberta livre estática (SALE), confeccionada a partir de garrafa de plástico transparente de politereftalato de etileno (PET) de 2 L. O interior da câmara apresentava livre circulação de ar, e possuía uma lâmina de espuma de poliuretano, com 2,5 cm de largura e 25 cm de comprimento, pendurada verticalmente, com a extremidade inferior inserida em frasco com solução ácida, que mantinha a espuma saturada. A recuperação do 15 N-NH 3 no coletor aumentou de forma linear com o aumento da taxa de volatilização de NH 3 do solo. Os testes de campo mostraram efi ciência de 57% na recuperação do N-NH 3 volatilizado do solo. O intervalo de coletas das espumas pode variar de um a seis dias, sem comprometer a efi ciência do sistema. Para estudos de campo, com uso do método proposto, o fator de correção de 1,74 deve ser usado para estimar a real taxa de volatilização de amônia do solo.Termos para indexação: fator de emissão de amônia, isótopo 15 N, sistema coletor de NH 3 , ureia, volatilização de amônia.
Calibration of a semi-opened static chamber for the quantifi cation of volatilized ammonia from soilAbstract -The objective of this work was to calibrate a practical and low-cost chamber for the quantifi cation of ammonia volatilization from soil. The chamber was calibrated using the 15 N isotope balance technique. The volatilized ammonia was captured by a semi-opened free static chamber built with a 2 L ethylene polyterephthalate (PET) plastic bottle. The inner side of the chamber had free-air circulation and a stripe of polyurethane foam, with 2.5 cm wide and 25 cm long, hanged vertically with the lower end inserted in a bottle containing acid solution, which kept the foam moistened. The recovery of 15 N-ammonia by the chamber increased linearly with the increase in the rate of soil ammonia volatilization. Field tests showed an effi ciency of 57% in the volatilized ammonia recuperation. The sampling interval of foam can vary from one to six days without impairing the system effi ciency. For studies in the fi eld using the proposed method, a correction factor of 1.74 should be used to estimate the real rate of ammonia volatilization from soil.
Termos para indexação: complexos orgânicos, mobilidade de cátions, cálcio, alumínio.
DYNAMIC OF IONS IN ACID SOIL LEACHED WITH GREEN MANURE RESIDUES EXTRACTS AND PURE SOLUTIONS OF ORGANIC ACIDSABSTRACT -The influence of green manure residues addition in the dynamic of ions in acid soils is not well known. In this study, ion mobility in a sample of the Bw horizon of an Dark-Red Latosol (Oxisol), leached with citric and succinic acid pure solutions and with aqueous residue extracts of black oats (Avena strigosa) and oil seed radish (Raphanus sativus) were evaluated in soil columns (5, 10, 20, and 40 cm long by 4 cm diameter). After the solutions and extracts passed through the soil columns, the following parameters were determined: solubles contents of Ca s , Mg s , K s , Al st (total), Al so (organic), Al sm (monomeric) and dissolved organic carbon. In soil, the parameters evaluated were the exchangeable contents of Ca ex , Mg ex , K ex , and Al ex and pH (CaCl 2 ). Citric and succinic acids increased Al st and Ca s contents, respectively, resulting in decreasing exchangeable fractions of these elements in soil. Black oats extract was more effective to extract Ca ex and oil seed radish to extract Al ex . The decrease in Ca ex and Al ex was followed by an increase in K ex . Organic complexes formed with low molecular organic ligands and Ca s and Al ex were suggested to play a role in the mobility of ions in subsoils of acid soils after the addition of both crop residues extracts and pure organic acid solutions.
RESUMO: O calcário aplicado na superfície do solo apresenta baixa eficiência na correção da acidez subsuperficial. A eficiência pode ser melhorada através de compostos orgânicos hidrossolúveis liberados pelos resíduos vegetais. Foi avaliado um método biológico para testar a capacidade de extratos vegetais na mobilização do calcário no solo. O método consiste das seguintes etapas: coleta e preparo do material vegetal; extração dos compostos orgânicos hidrossolúveis; preparo da coluna de solo; aplicação do calcário na superfície do solo; aplicação do extrato vegetal; irrigação com água destilada; teste biológico com a planta indicadora de trigo cv. Anahuac e avaliação do crescimento radicular. A calagem sem resíduo vegetal aumentou o pH e o teor de Ca e diminuiu o teor de Al apenas na camada 0 a 5 cm de profundidade. A calagem com resíduos de aveia preta e nabo forrageiro aumentou o pH e o teor de Ca e diminuiu o teor de Al na camada de 0 a 20 cm de profundidade. Por outro lado, a calagem com resíduos de trigo não afetou a mobilidade do calcário no solo. O crescimento das raízes acompanhou os efeitos na química do solo: calagem sem resíduo e calagem com resíduo de trigo apresentaram crescimento das raízes até 10 cm de profundidade enquanto a calagem com resíduos de aveia e nabo favoreceu o crescimento das raízes até 20 cm de profundidade. O teste biológico foi adequado para avaliar a eficiência de resíduos vegetais na mobilização do calcário no solo. Palavras-chave: calagem, acidez subsuperficial, teste biológico, lixiviação
PLANT RESIDUE EXTRACTS POTENTIAL FOR LIME MOBILITY IN THE SOIL USING A BIOLOGICAL METHODABSTRACT: Soil surface applied lime shows low efficiency in alleviating subsoil acidity. Lime efficiency is increased through water-soluble organic compounds released from plant residues. A biological test was evaluated to verify the capacity of plant extracts on lime mobility in the soil. The test presents the following steps: plant material preparation; extraction of water soluble organic compounds; soil column preparation; soil surface lime addition; plant extract addition; irrigation with distillated water; biological test with an indicator plant (wheat, cultivar Anahuac); and root growth evaluation. Surface applied lime without plant residue increased pH and Ca, and decreased Al in the top 5 cm of soil. Lime with black oats and oil seed radish extracts increased pH and Ca and decreased Al up to the 20 cm soil depth. Wheat residue had no effect on lime mobility. Indicator root growth followed the effect of treatments on soil chemical composition: lime without plant residue enhanced root growth in the top 10 cm depth and lime with black oats and oil seed radish enhanced root growth up to the 20 cm depth. The biological test was efficient to evaluate the ability of plant residues in relation to lime mobility in the soil.
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