Structural changes and degradation of Red Latosols under different management systems for 20 years

Abstract

SUMMARYSoils are the foundation of terrestrial ecosystems and their role in food production is fundamental, although physical degradation has been observed in recent years, caused by different cultural practices that modify structures and consequently the functioning of soils. The objective of this study was to evaluate possible structural changes and degradation in an Oxisol under different managements for 20 years: no-tillage cultivation with and without crop rotation, perennial crop and conventional tillage, plus a forested area (reference). Initially, the crop profile was described and subsequently, 10 samples per management system and forest soil were collected to quantify soil organic matter, flocculation degree, bulk density, and macroporosity. The results indicated structural changes down to a soil depth of 50 cm, with predominance of structural units ∆µ ∆µ ∆µ ∆µ ∆µ (intermediate compaction level) under perennial crop and no-tillage crop rotation, and of structural units ∆ ∆ ∆ ∆ ∆ (compacted) under conventional tillage and no-tillage. The soil was increasingly degraded in the increasing order: forest => no-tillage crop rotation => perennial crop => no-tillage without crop rotation => conventional tillage. In all managements, the values of organic matter and macroporosity were always below and bulk density always above those of the reference area (forest) and, under no-tillage crop rotation and perennial crop, the flocculation degree was proportionally equal to that of the reference area.Index terms: crop profile, soil physical properties, organic matter, soil quality. RESUMO: MUDANÇAS ESTRUTURAIS E DEGRADAÇÃO DE ATRIBUTOS DE LATOSSOLO VERMELHO SUBMETIDO A DIFERENTES MANEJOS POR 20 ANOSO solo integra os ecossistemas terrestres e o papel dele na produção de alimentos é essencial, embora nos últimos anos tenha se constatado sua degradação física em razão das diferentes práticas culturais utilizadas que modificam sua estrutura e, consequentemente, seu funcionamento. O objetivo deste trabalho foi avaliar possíveis mudanças estruturais, bem como a degradação de Latossolo Vermelho submetido a diferentes manejos por 20 anos. As avaliações foram realizadas em diferentes manejos: semeadura direta com e sem rotação de culturas; cultura perene; e preparo convencional, além de uma área de mata (referência). Inicialmente, fez-se a descrição do perfil cultural e, na sequência, coletaram-se 10 amostras de solo em cada manejo considerado e sob mata nativa para quantificar o teor de matéria orgânica, o grau de floculação, a densidade e a macroporosidade do solo. Os resultados indicaram mudanças estruturais até 50 cm de profundidade com predomínio de unidades estruturais ∆µ (nível intermediário de compactação) nos manejos cultura perene e semeadura direta com rotação de culturas e unidades estruturais ∆ (compactado), nos manejos preparo convencional e semeadura direta. A degradação do solo, da menor para a maior, ocorreu na seguinte ordem: Mata => semeadura direta com rotação de culturas => cultura perene => semeadura dir...

Physico-chemical attributes of a Cambisol under pasture managed with annual burns after sugarcane vinasse application

“…Some organic compounds such as proteins (Nelson et al 1999) and low molecular weight organic compounds (Nguyen et al 2013) can act as clay dispersants. However, organic molecules, such as the aliphatic ones (Nelson et al 1999), can also bind two or more clays together, which increases aggregate stability (Bronick and Lal 2005) and clay flocculation (Tavares Filho et al 2014). In addition, vinasse increases microbiological activity, which can release exudates and increase soil aggregation (Bronick and Lal 2005).…”

Physical Properties of Soil Structures Identified by the Profil Cultural under Two Soil Management Systems

“…The cultivated layer is subject to considerable spatial variability, unlike horizons that are not usually affected by tillage (Neves et al, 2003;Fuentes-Llanillo, 2013;Gonçalves et al, 2013;Tavares Filho et al, 2014;Boizard et al, 2016). This variability often allows plants to grow in compacted soils, taking advantage of the flow of water and gas through structural discontinuities (cracks) that also allow root growth (Neves et al, 2003;Reichert et al, 2016).…”

“…This complexity has led to the use of a wide range of quantitative methods of analysis. Furthermore, the spatial variability of physical soil properties makes it difficult to represent the real situation (Tavares Filho et al, 1999;Neves et al, 2003;Llanillo et al, 2006;Fuentes-Llanillo et al, 2013;Silva et al, 2014;Tavares Filho et al, 2014). These difficulties arise because most results are obtained from laboratory evaluations of random samples taken at specific depths, without taking the heterogeneous nature of the soil structure into account.…”

“…Studies have shown that this method of soil profile analysis can be helpful in qualitative evaluation of soil management (Coulomb et al, 1993;Roger-Estrade et al, 2000b;Mueller et al, 2009;Mueller et al, 2013;Munkholm et al, 2013;Guimarães et al, 2013;Tavares Filho et al, 2014;Boizard et al, 2016). It enables researchers to establish links between soil structure and other factors, such as root development (Roger-Estrade et al, 2000a;Mentges et al, 2016), the availability and distribution of minerals (Vizier et al, 1995), and hydrodynamic characteristics (Mentges et al, 2016).…”

“…Soil profile analysis also allows visualization of soil compaction and can help in collection of samples for laboratory analysis (Neves et al, 2003;Portella et al, 2012;Guimarães et al, 2013;Silva et al, 2014;Tavares Filho et al, 2014;Boizard et al, 2016). This method is an important diagnostic tool for field use, especially when studying soil compaction problems (Neves et al, 2003).…”