Effects of different management systems on porosity of oxisols in Paraná, Brazil

Abstract

SUMMARYSoils play a fundamental role in the production of human foods. The Oxisols in the state of Paraná are among the richest and most productive soils in Brazil, but degradation and low porosity are frequently documented, due to intensive farming involving various management strategies and the application of high-tech solutions. This study aims to investigate changes in the porosity of two Red Oxisols (Latossolos Vermelhos), denoted LVef (eutroferric) and LVdf (dystroferric) under conventional and no-tillage soil management, with a succession of annual crops of soybean, maize and wheat over a continuous period of more than 20 years. After describing the soil profiles under native forest, no-tillage management and conventional tillage using the crop profile method, deformed and non-deformed soil samples were collected from the volumes most compacted by human intervention and the physical, chemical and mineralogical properties analyzed. The various porosity classes (total pore volume, inter-aggregate porosity between channels and biological cavities) and intra-aggregate porosity (determined in 10 cm 3 saturated clods subjected to a pressure of -10 kPa to obtain a pore volume with a radius (r eq ), ≥ ≥ ≥ ≥ ≥ 15 μ μ μ μ μm and < 15 μ μ μ μ μm). The results showed that the effects of no-tillage farming on porosity are more pronounced in both soil types. Porosity of the LVdf was higher than pf the LVef soil, whatever the management type. In the LVdf soil, only pores with a radius of > 15 μ μ μ μ μm were affected by farming whereas in the LVef soil, pores with a radius of < 15 μ μ μ μ μm were affected as well.Index terms: soil structure, crop profile method, no-tillage, conventional tillage.(1) Part of thesis the first author.

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

“…The Ma data indicated that the CT and NT were very close to this limit (10 %), which suggested that these areas were already affected by limited plant growth. This reinforced previous results that showed how management strategies involving the use of increasingly larger machines without considering the soil moisture content or without crop rotation facilitate short and long-term compaction (Silva et al, 2000;Tavares Filho et al, 2010Baquero et al, 2012;Llanillo et al, 2006Llanillo et al, , 2013. This idea is reinforced in the radial graphs for the proportional values for the 0-50 cm layer for OM, FD, Bd and Ma (Figure 4).…”

“…This finding agrees with results of Silva et al (2000) but disagrees with the findings of Silveira et al (1999) and Silveira Neto et al (2006). In addition, these results reinforce the fact that more intensive soil tillage and equipment traffic on the soil surface (especially under inadequate moisture conditions with increased OM degradation on the soil surface) results in greater soil degradation (Neves et al, 2007;Tavares Filho et al, 2010Baquero et al, 2012;Llanillo et al, 2006Llanillo et al, , 2013Calegari et al, 2013).…”

“…Therefore, between Co and the different management systems, Ma decreased from 0.09 m 3 m -3 in the NTR, to 0.12 m 3 m -3 in the PC and 0.19 m 3 m -3 in the CT and NT management systems. An increase in Bd reduces soil porosity (mainly Ma) by an order of 0.01 m 3 m -3 in the soil pore volume, which corresponds to a decrease of 10 m 3 Mg -1 in the total number of soil pores (Tavares Filho et al, 2010Baquero, et al, 2012). Therefore, for a soil volume of 1 ha to a depth of 0.20 m, the macropores were reduced by 7.20 m 3 ha -1 in the NTR and PC management systems, by 7.60 m 3 ha -1 in the CT management system and by 11.20 m 3 ha -1 in the NT management system, compared to Co.…”

“…However, soil degradation has recently become a major environmental problem. In the State of Paraná, the Red Latosol is one of the richest and most productive soil types for grain production for Brazilian domestic and export markets (Tavares Filho et al, 2010;. However, the intensive soil use with agricultural technologies and a wide range of management and agricultural practices has resulted in soil physical degradation and structural changes, e.g., the formation of compacted layers (Collares et al, 2006;Portella et al, 2012;Llanillo et al, 2013;Calegari et al, 2013).…”

Morfologia e propriedades físicas de solo segundo sistemas de manejo em culturas anuais

“…Após a incorporação desses solos ao sistema produtivo problemas de degradação física, sobretudo alterações estruturais e compactação do solo, têm sido observados (Assouline et al, 1997;Tavares Filho et al, 1999, 2001Giarola et al, 2007;Tavares Filho &Tassier, 2009, Tavares Filho & Tessier, 2010 e embora esses problemas possam existir desde o início da agricultura, sua extensão e seu impacto são considerados, hoje, de extrema intensidade (Lal & Stewart, 1990). Portanto, o diagnóstico qualitativo de diferentes estruturas a campo, complementado pelas análises laboratoriais, pode ajudar na tomada de decisão quanto ao tipo de manejo a ser empregado no solo para manutenção ou melhoria da produtividade (Tavares Filho &Tassier, 2009;.…”