Estabilidade de agregados e distribuição de carbono e nutrientes em Argissolo sob adubação orgânica e mineral

Abstract

Resumo -O objetivo deste trabalho foi avaliar o impacto da adubação orgânica e mineral sobre a estabilidade de agregados e a distribuição de C, N e P, em classes de agregados de um Argissolo Vermelho-Amarelo. Os tratamentos consistiram de 0 e 40 m 3 ha -1 por ano de adubação orgânica e de 0, 250 e 500 kg ha -1 de adubação mineral N-P-K da fórmula 4-14-8. Uma área sob floresta atlântica foi utilizada como referência. Amostras foram coletadas nas camadas de 0-10 e 10-20 cm. Houve predomínio da classe de agregados entre 4 e 2 mm, que correspondeu a 39,7% do total de agregados separados por via seca no tratamento com composto orgânico. Os teores de C orgânico total para adubação orgânica foram 17,5 e 36,7% maiores para as classes 4-2 e 0,105-0,25 mm. A adubação orgânica contribuiu para teores de N e P totais de 43 e 38,7% (0-10 cm) e 35,4 e 36,8% (10-20 cm), maiores que os dos tratamentos sem adubo orgânico. A relação carbono/nitrogênio se manteve constante entre as classes de agregados de um mesmo tratamento, enquanto a de carbono/fósforo reduziu com o uso de adubo orgânico ou mineral, em relação à mata nativa. Os índices de estabilidade de agregados se correlacionaram positivamente aos teores de carbono orgânico total da classe 4-2 mm.Termos para indexação: agregação, estrutura do solo, matéria orgânica, sistema de manejo. Aggregate stability and carbon and nutrients distribution in an Acrisol under organic and mineral fertilizationAbstract -The aim of this work was to evaluate the effect of mineral and organic fertilization on the soilwater aggregate stability and on the distribution of C, N and P in different classes of aggregates in an Acrisol. The treatments were 0 and 40 m 3 ha -1 per year of organic fertilizer and 0, 250 and 500 kg ha -1 of mineral fertilizer N-P-K of the formula 4-14-8. An area under Atlantic forest was used as reference. Soil samples were collected at 0-10 and 10-20 cm depths. The distribution of aggregates showed the highest values from 4 to 2 mm. In the organic fertilizer treatment, the aggregates 4-2 mm corresponded to 39.7% of the total on the soil. For the aggregates 4-2 and 0.105-0.25 mm, the total organic carbon contents were 17.5 and 36.7% higher in the organic fertilizer treatments. The organic fertilization contributed to values of N and P of 43 and 38.7% (0-10 cm) and 35.4 and 36.8% (10-20 cm), which were higher than the treatments without organic fertilizer. The carbon/nitrogen ratio did not vary among the aggregate classes in the same treatment. However, the carbon/ phosphorus ratio was reduced with the use of organic and mineral fertilizer. The indexes of aggregates stability were positively correlated with the content of total organic carbon in the 4-2 mm.Index terms: aggregation, soil structure, organic matter, management system. IntroduçãoA busca por sistemas conservacionistas, que minimizem as emissões de gases do efeito estufa e que contribuam para a manutenção das qualidades física e química do solo, têm relacionado a matéria orgânica (MO) como importante índice na aval...

Changes in a Rhodic Hapludox under no-tillage and urban waste compost in the northwest of Rio Grande do Sul, Brazil

“…In this study, the response of carbon and nitrogen contents to different UWC rates was similar, since, regardless of the treatment, the C:N ratio (11:1) was constant ( Table 5). These results agree with those of Matos et al (2008), who observed an increase in carbon stocks and soil aggregate stability from the application of organic fertilizer. Rozane et al (2010) evaluating the effect of management systems on aggregate stability, observed that GMD and MWD were higher in the 0.0-0.10 m layer, related to the increase in SOC content.…”

“…In the 2009/ 10 growing season, results were similar for both GMD and MWD (Figure 1), with a linear increase in the quantity of aggregates retained in the sieve class 8.00-4.76 mm, indicating that aggregate stability increases with UWC application on the soil. This may be related to greater root growth and the contribution of organic matter, as also reported by Matos et al (2008).…”

“…Matos et al (2008) observed increases in SOC contents over time with the use of organic fertilizer (common bean and soybean straw + cattle manure). However, Pinto et al (2012) found that the soil carbon stock of an Oxisol varied in a quadratic manner in relation to the increased application of waste from turkey litter.…”

“…However, the use of 100 m 3 ha -1 in the 2010/11 growing season induced no differences in GMD and MWD compared to mineral fertilizer, which can be associated, partly, to the predominance of the dispersing effect of the chemical elements (Medeiros (Oades, 1984) on the aggregating effects observed in the second year. Thus, the continuous use of mineral fertilizers over time can reduce soil aggregate stability (Matos et al, 2008).…”

“…The evolution of the soil aggregation state improves the soil structure, which can consequently increase soil porosity, aeration, infiltration and erosion resistance (Matos et al, 2008;Vezzani & Mielniczuk, 2009;Bonini & Alves, 2011;Santi et al, 2012). The increase in the proportion of macroaggregates and the high organic carbon contents can characterize an improved soil structure, because the soil properties reach levels at which soil functions are fully operational (Vezzani & Mielniczuk, 2009).…”