Aggregate stability as affected by short and long-term tillage systems and nutrient sources of a hapludox in southern Brazil

Abstract

SUMMARYThe ability of a soil to keep its structure under the erosive action of water is usually high in natural conditions and decreases under frequent and intensive cultivation. The effect of five tillage systems (NT = no-till; CP = chisel plowing and one secondary disking; CT = primary and two secondary distings; CTb = CT with crop residue burning; and CTr = CT with removal of crop residues from the field), combined with five nutrient sources (C = control, no nutrient application; MF = mineral fertilizers according to technical recommendations for each crop; PL = 5 Mg ha -1 y -1 fresh matter of poultry litter; CM = 60 m 3 ha -1 y -1 slurry cattle manure; and SM = 40 m 3 ha -1 y -1 slurry swine manure) on wet-aggregate stability was determined after nine years (four sampled soil layers) and on five sampling dates in the 10 th year (two sampled soil layers) of the experiment. The size distribution of the air-dried aggregates was strongly affected by soil bulk density, and greater values of geometric mean diameter (GMD AD ) found in some soil tillage or layer may be partly due to the higher compaction degree. After nine years, the GMD AD on the surface was greater in NT and CP compared to conventional tillage systems (CT, CTb and CTr), due to the higher organic matter content, as well as less soil mobilization. Aggregate stability in water, on the other hand, was affected by the low variation in previous gravimetric moisture of aggregates, which contributed to a high coefficient of variation of this attribute. The geometric mean diameter of water-stable aggregates (GMD WS ) was highest in the 0.00-0.05 m layer in the NT system, in the layers 0.05-0.10 and 0.12-0.17 m in the CT, and values were intermediate in CP. The stability index (SI) in the surface layers was greater in treatments where crop residues were kept in the field (NT, CP and CT), which is associated with soil organic matter content. No differences were found in the layer 0.27-0.32 m. The effect of nutrient sources on GMD AD and GMD WS was small and did not affect SI.Index terms: soil tillage, manure, sampling time, soil structure, aggregation. RESUMO: EFEITOS DE CURTO E DE LONGO PRAZO DA APLICAÇÃO DE SISTEMAS DE MANEJO DO SOLO E DE FONTES DE NUTRIENTES SOBRE A ESTABILIDADE DE AGREGADOS, EM UM NITOSSOLO VERMELHO

Soil Aggregation, Organic Carbon Concentration, and Soil Bulk Density As Affected by Cover Crop Species in a No-Tillage System

“…Therefore, increasing soil organic C often leads to better soil aggregation. Similar results were reported by other authors for the tropical regions (Six et al, 1999;Madari et al, 2005;Salton et al, 2008;Veiga et al, 2009;Souza et al, 2009;Garcia and Rosolem, 2010). In addition, Six et al (1999) showed that due to the increase in organic matter, smaller aggregates coalesce into larger aggregates, improving soil structure.…”

Water-Stable Aggregates and Associated Carbon in a Subtropical Rice Soil Under Variable Tillage

“…In the upper 0.00-0.05 and 0.05-0.20 m layers, the NT system improved the formation level of the >2 mm aggregate but reduced the formation level of <0.053 mm aggregates, compared to the MP system, suggesting that mechanical operation reduced large-macroaggregate formation and disrupted soil macroaggregates into individual particles. Similar results have also been reported by Wohlenberg et al (2004), Veiga et al (2009 and Jiang et al (2011). The higher proportion of >2 mm aggregates and lower proportion of <0.053 mm aggregates under NT systems might be the result of the higher soil hydrophobicity, low intensity of wetting and drying cycles, higher soil C concentration or the physical and chemical characteristics of large macroaggregates making them more resistant to breaking up (Balesdent et al, 2000;Eynard et al, 2006;Vogelmann et al, 2013).…”

“…Positive effects of straw application on macroaggregate formation and stability have also been reported by other workers (Singh et al, 2007;Veiga et al, 2009;Bandyopadhyay et al, 2010).…”

Evolução de atributos físicos de solo em sistema de integração lavoura-pecuária

“…Isso indica que a presença dos animais pode contribuir para a estabilização de agregados pelo efeito do pisoteio, ao promover a aproximação de partículas minerais. Assim, o aumento da densidade do solo pode proporcionar agregados mais estáveis (Veiga et al, 2009).…”