Jessé Rodrigo Fink

Iron oxides dynamics in a subtropical Brazilian Paleudult under long-term no-tillage management

Replacing conventional tillage (CT) with no-tillage (NT) management alters the pedoenvironment and the rate of topsoil processes, with possible effects on dissolution processes associated with iron oxides and therefore soil mineralogy. This study aimed to determine the effect of NT on the content and distribution of types of iron oxides in a Rhodic Paleudult in southern Brazil. Soil samples were collected at eight depths within the 0.00-0.80 m layer under CT and NT in a long-term experiment (21 years). Mineralogical identification was conducted by X-ray diffraction (XRD), and the Fe content related to specific types of iron oxides determined by selective dissolution and diffuse-reflectance spectroscopy. Kaolinite, quartz, goethite, hematite, and maghemite were identified in the clay fraction. In the NT-managed soil, there was a decrease in the content of crystalline iron oxides and an increase in the content of poorly crystalline iron oxides with increasing proximity to the soil surface. These results suggest that iron oxides are rearranged in this soil by reductive dissolution of the crystalline types and neoformation of metastable ferrihydrite in topsoil layers, which should be assessed further in laboratory studies.

Iron oxides and organic matter on soil phosphorus availability

A continua expansao da producao agricola tem levado a uma crescente demanda de fertilizantes fosfatados. O conhecimento da dinâmica do fosforo no solo e suas interacoes com oxidos de ferro e materia orgânica podem ser uteis no desenvolvimento de estrategias eficientes para o manejo sustentavel, especialmente em um cenario de crescente escassez de fontes de minerais fosfatados. Nesta revisao bibliografica foi abordado a relacao do fosforo com oxidos de ferro e materia orgânica, e seu efeito na disponibilidade de fosforo. As culturas, normalmente, obtem fosfato de minerais intemperizados ou fertilizantes dissolvidos. No entanto, a quantidade de fosforo presente na solucao do solo depende das reacoes de adsorcao e dessorcao por oxidos de ferro, as quais podem ser influenciadas por interacoes com a materia orgânica. Portanto, os sistemas de recomendacao de fertilizantes com base em metodologias que consideram as interacoes entre componentes do solo, tais como oxidos e materia orgânica, e a capacidade de adsorcao de fosforo, resultantes de tais interacoes (por exemplo, analise de P remanescente), pode ser mais confiavel para garantir o uso eficiente e racional de fertilizantes fosfatados.

Morfologia dos contatos entre solo-saprolito-rocha em neossolos derivados de arenitos da formação caturrita no Rio Grande do Sul

The use of the shallow Neossolos (Leptosols and Regosols) is limited in view of the small depth and rock fragments on the surface. There is a lack of information about the definition of the contacts between soil, saprolite and rock in this soil class, as well as tools that would facilitate the morphologic field identification. The objectives of this research were an evaluation of the morphology of the contact between soil, saprolite and rock in the Neossolos derived from the sandstones of the Caturrita Formation, in the central area of Rio Grande do Sul State; to test and to adapt the weathering classes of Pedron et al. (2009) to the conditions of sedimentary rock; and to verify the correlation of the weathering classes with penetration resistance. It was stated that the morphology of the saprolithic layers of the Neossolos Litolicos (Leptosols) and Neossolos Regoliticos (Regosols) derived from sandstone are similar to the same soil classes derived from volcanic rocks in the State, allowing the adaptation of the same weathering classes proposed by Pedron et al. (2009). The tests with the impact penetrometer showed high correlation with the weathering classes adapted in this study. The following contacts were identified in the studied profiles: lithic contact, lithic fragmentary contact, and saprolithic fragmentary contact. The authors suggest, considering its importance, the inclusion of this latter in the Brazilian soil classification system.

Diffusion and uptake of phosphorus, and root development of corn seedlings, in three contrasting subtropical soils under conventional tillage or no-tillage

Soil mineralogy and management can have substantial effects on phosphorus (P) diffusion in soil and hence on root morphology. The aim of this study was to assess these effects in soils differing widely in P-sorbing components. Samples of a Rhodic Paleudult (RP), a Rhodic Hapludox (RH), and a Humic Hapludox (HH) under conventional tillage (CT) or no-tillage (NT) were placed in Petri dishes to assess P diffusion. Performance and root morphology in corn grown on soil samples subjected to three different P fertilization treatments (no fertilizer, surface, and deep fertilizer application) were examined. Phosphorus diffusion was slower in the HH than in the other soils by effect of its high P adsorption capacity because of its mineralogy. Soil management had no effect on P diffusion. Fertilization with P only affected plant-related variables in RH: surface fertilization increased root biomass, and deep fertilization shoot biomass and proportion of thick roots. Soil management affected plants growing on HH and RP: the plants grown under NT were taller (RP) and developed more fine roots (HH) than those under CT. Fertilization with P had little effect on plant growth in the goethite-rich soil (HH) or the one with high content in available P (RP). Our results suggest that management system in these soils has therefore greater influence on fertility than fertilization treatment.

Chemical and mineralogical changes in a Brazilian Rhodic Paleudult under different land use and managements

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.

Atributos químicos e área superficial específica em Latossolo subtropical de altitude sob usos e manejos distintos

The original landscape of Campos de Cima da Serra region has changed by anthropogenic interference. The study aimed to evaluate soil chemical and physical attributes of an Oxisol under natural grassland (CN), burned natural grassland (CNq), natural forest (MN), pine afforestation (PF) and annual crops in conventional tillage system (LA), in the 0.00-0.025, 0.025-0.05, 0.05-0.10, 0.10-0.20, 0.20-0.30m layers. The mineralogy was evaluated by X-ray diffraction. It was evaluated the total organic carbon (TOC); pH (H2O); exchangeable Ca, Mg, K, Na and Al; H+Al and P contents; and calculated bases sum (S), cation exchange capacity (CEC) and bases and Al saturation on CEC. It was estimated soil specific surface area (SSA) and maximum phosphorus adsorption capacity (MPAC). The soil showed kaolinitic and oxidic mineralogy. In the CN soil TOC content ranged between 15.3 and 56.4g kg-1, pH values ≤4.8; CEC was high (18<CECpH7<22 cmolc dm-3) with low bases saturation (3<V<34%) and high Al saturation (23<m<88%). Related to CN soil, TOC contents increased in the MN surface was similar for the CNq and decreased for the FP and LA areas. Soil fertility was positively modified in MN and CNQ areas, and reduced under FP, and was conditioned by TOC. The TOC content was positively related to soil ASE and negatively with soil MPAC.

Condutividade e retenção de água em neossolos e saprolitos derivados de arenito

SUMMARY : HYDRAULIC CONDUCTIVITY AND WATER RETENTION INLEPTOSOLS-REGOSOLS AND SAPROLITE DERIVED FROMSANDSTONE, BRAZIL Leptosols and Regosols are soils with a series of restrictions for use, mainly related to theeffective depth, which have been poorly studied in Brazil. These soils, when derived fromsedimentary rocks should be treated with particular care to avoid environmental damage suchas aquifer contamination. The purpose of this study was to verify the behavior of hydraulicconductivity and water retention capacity in profiles of Leptosols and Regosols derived fromsandstone of the Caturrita formation in Rio Grande do Sul state. The morphology, particlesize distribution, porosity, soil density (Ds), saturated hydraulic conductivity (K s ), basic waterinfiltration in the field (BI) and water retention were determined in soil and saprolite samplesof six soil profiles. High Ds, low macroporosity and high microporosity were observed in theprofiles, resulting in a low K s and BI, even under conditions of sandy texture and a highlyfractured saprolite layer. The variation coefficients of data of K

Propriedades físicas do solo e crescimento de raízes de milho em um argissolo vermelho sob tráfego controlado de máquinas

Soil functions can be hampered by compaction induced by inadequate management. Some soil physical properties are indicators of the existence of compacted layers that can affect the root development of crops. Agricultural practices, e.g., planting of cover crops to improve soil properties, can mitigate the compaction-related problems. The aim of this study was to evaluate the physical attributes of soil and plants, grown under controlled conditions. In an Ultisol under no-tillage with two winter cover crops (fallow and oat + vetch) and controlled machine traffic (no traffic -NT, before traffic - BT and after traffic - AT), we evaluated the pre-consolidation pressure, penetration resistance, soil bulk density, porosity, and average diameter of aggregates. Undisturbed soil samples were collected before and after traffic, filled into PVC pots and placed in a greenhouse. Three corn seeds were sown per pot and grown for 25 days under different conditions of water availability. After this period, the leaf area and the fresh and dry matter of corn shoots and roots were determined. Regardless of the layer, bulk density was not affected by the soil cover, but was influenced by machine traffic. Macroporosity in the fallow plot was affected by traffic to a depth of 0.10 m, indicating the reduced capacity of this system to resist disturbances, evidenced also by the lower pre-consolidation pressure. Resistance to penetration increased with depth, and was related to higher density, lower macroporosity and higher pre-consolidation pressure. Without water stress, maize root growth was positively influenced by machine traffic. Under the tested experimental conditions, no-tillage with crop rotation was more resilient to soil disturbances than the other system.

Caracterização de plintitas e petroplintitas em solos da depressão central do Rio Grande do Sul

The presence, composition and distribution of ferruginous concretions in the soil, called plinthite and petroplinthites, are conditioned to the environmental characteristics of the region, attributing intrinsic properties to the soil. The objective of this study was to understand the composition of plinthite and petroplinthites, of soils at the Central Depression of Rio Grande do Sul state, Brazil, by the evaluation of chemical and mineralogical characteristics of these features. For this, chemical, morphological and particle size characterization of three soil profiles, was performed. The ferruginous concretions present in some horizons were separated from the soil matrix and submitted, separately to successive procedures for selective extraction of Fe and Al. The horizons of the soils showed a wide variation of textures and chemical attributes such as pH, S, V, m and MO. The levels of Feh, Feo and Fed followed the trend of the soil matrix <plinthite <petroplinthites. Among the oxides of Fe, there was higher incidence of hematite mineral in all samples.

Óxidos de ferro e área superficial de Latossolo subtropical sob campo e floresta nativa

The current weather conditions indicate a substitution of grassland by forest vegetation in the Campos de Cima da Serra in Rio Grande do Sul, Brazil. This change in vegetation changes the contents of soil organic matter and soil moisture. This study aimed to evaluate the pedogenetic iron oxides in an Oxisol under native forest and grassland and its relationship with soil total organic carbon content and soil specific surface area. Replacing grassland with native forest resulted in an accumulation of soil organic carbon and possibly influenced dissolutive processes of crystalline iron oxides types and neoformation of metastable types of low crystallinity. In native forest soil, the increase of total organic carbon increased the soil specific surface area, masking the positive effect of iron oxides on this physical characteristic.