Abstract
Changes in land use and management can affect the dynamic equilibrium of soil systems and induce chemical and mineralogical alterations. This study was based on two long-term experiments (10 and 27 years) to evaluate soil used for no-tillage maize cultivation, with and without poultry litter application (NTPL and NTM), and with grazed native pasture fertilized with cattle droppings (GrP), on the chemical and mineralogical characteristics of a Rhodic Paleudult in Southern Brazil, in comparison with the same soil under native grassland (NGr). In the four treatments, soil was sampled from the 0.0-2.5 and 2.5-5.0 cm layers. In the air-dried fine soil (ADFS) fraction (∅ < 2 mm), chemical characteristics of solid and liquid phases and the specific surface area (SSA) were evaluated. The clay fraction (∅ < 0.002 mm) in the 0.0-2.5 cm layer was analyzed by X-ray diffraction (XRD) after treatments for identification and characterization of 2:1 clay minerals. Animal waste application increased the total organic C concentration (COT) and specific surface area (SSA) in the 0.0-2.5 cm layer. In comparison to NGr, poultry litter application (NTPL) increased the concentrations of Ca and CECpH7, while cattle droppings (GrP) increased the P and K concentrations. In the soil solution, the concentration of dissolved organic C was positively related with COT levels. With regard to NGr, the soil use with crops (NTM and NTPL) had practically no effect on the chemical elements in solution. On the other hand, the concentrations of most chemical elements in solution were higher in GrP, especially of Fe, Al and Si. The Fe and Al concentrations in the soil iron oxides were lower, indicating reductive/complexive dissolution of crystalline forms. The X-ray diffraction (XRD) patterns of clay in the GrP environment showed a decrease in intensity and reflection area of the 2:1 clay minerals. This fact, along with the intensified Al and Si activity in soil solution indicate dissolution of clay minerals in soil under cattle-grazed pasture fertilized with animal droppings.
Highlights
In the past, the formation and stability of minerals were determined by soil-environmental conditions, which enable the use of these minerals as indicators of current and past pedogenetical processes (Kämpf & Curi, 2000; 2003)
The specific surface area (SSA) values increased in the surface layer of land uses and management of the soils to which animal waste was applied (NTPL and grazed pasture (GrP))
Compared with native grassland (NGr), animal waste application did not alter SSA in the 0.0-2.5 cm layer, which was reduced by maize cultivation with no poultry litter application (NTM)
Summary
The formation and stability of minerals were determined by soil-environmental conditions, which enable the use of these minerals as indicators of current and past pedogenetical processes (Kämpf & Curi, 2000; 2003). The alternating oxidizing and reducing conditions at the soil microsites can induce iron oxide mobilization and have been used to explain the new dynamic (redistribution) of these minerals in soil surfaces where a conventional tillage (CT) was replaced by a no-tillage (NT) system (Silva Neto et al, 2008; Inda et al, 2013). In these soils, the reductive/complexive dissolution of crystalline phases and the neoformation of new metastable phases was attributed to the accumulation of organic matter and increased moisture and residence time of water in NT soils
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