Abstract
Soils 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 cm³ saturated clods subjected to a pressure of -10 kPa to obtain a pore volume with a radius (r eq), > 15 μm and < 15 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 μm were affected by farming whereas in the LVef soil, pores with a radius of < 15 μm were affected as well.
Highlights
Soils play a fundamental role in the production of human foods (Lesturgez, 2005)
The geology is characterized by the Serra Geral Formation highlands, belonging to the São Bento Group, with fertile soils formed from a basalt volcanic eruption (Derrame de Trapp) which occurred in the Mesozoic era
The morphostructural organization of the soil was modified differently according to the type of crop management: under conventional tillage, soils (LVef and LVdf) in the 0–40 cm layer average, a compact morphostructural organization prevailed, with macroscopic discontinuity, subangular polyhedral aggregates and clods clearly separated by cracks, with predominantly rough fragmentation surfaces; under no-tillage cultivation, soils in the 0–60 cm layer average, a morphostructural organization with continuous compaction prevailed with little macroscopic discontinuity, and individual aggregates and clods that were difficult to differentiate due to the high level of cohesion between them, but when differentiated, they were normally angular polyhedral with mostly smooth fragmentation surfaces
Summary
Farming a given soil type in a reasonable manner depends directly on the availability of scientific data, since the pressure to meet the ever-increasing demand while ensuring sustainable development and respecting the environment is rarely compatible with the soils of complex ecosystems. This applies especially to tropical regions and in particular to Brazil (Leprun, 1994). In the State of Paraná, Red Oxisols derived from basalt are among the most productive in Brazil They are of fundamental importance to the State and the whole country, since they are used for both subsistence and cash crop agriculture. The agricultural use of these soils has been going on for some 70 years, and nowadays discussions regarding soil compaction have become quite common, regardless of the system employed (conventional or no-tillage)
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