Soil aggregation and the distribution of total organic carbon (TOC) may be affected by soil tillage and cover crops. The objective of this study was to determine the effects of crop rotation with cover crops on soil aggregation, TOC concentration in the soil aggregate fractions, and soil bulk density under a no-tillage system (NTS) and conventional tillage system (CTS, one plowing and two disking). This was a three-year study with cover crop/rice/cover crop/rice rotations in the Brazilian Cerrado. A randomized block experimental design with six treatments and three replications was used. The cover crops (treatments) were: fallow, Panicum maximum, Brachiaria ruziziensis, Brachiaria brizantha, and millet (Pennisetum glaucum). An additional treatment, fallow plus CTS, was included as a control. Soil samples were collected at the depths of 0.00-0.05 m, 0.05-0.10 m, and 0.10-0.20 m after the second rice harvest. The treatments under the NTS led to greater stability in the soil aggregates (ranging from 86.33 to 95.37 %) than fallow plus CTS (ranging from 74.62 to 85.94 %). Fallow plus CTS showed the highest number of aggregates smaller than 2 mm. The cover crops affected soil bulk density differently, and the millet treatment in the NTS had the lowest values. The cover crops without incorporation provided the greatest accumulation of TOC in the soil surface layers. The TOC concentration was positively correlated with the aggregate stability index in all layers and negatively correlated with bulk density in the 0.00-0.10 m layer.

/pdf/soil-aggregation-organic-carbon-concentration-and-soil-bulk-163e1wpfdo.pdf

Soil Aggregation, Organic Carbon Concentration, and Soil Bulk Density As Affected by Cover Crop Species in a No-Tillage System

The aim of this study was to evaluate the content and stock of total organic carbon in the soil and aggregates of a Red-Yellow Ultisol under management systems-conventional tillage with disc plow, disc plow plus harrow, harrow and only no-tillage system in an experiment conducted over 23 years in the Zona da Mata region, Minas Gerais, Brazil. A remnant of native forest was used as reference. Soil samples were collected at different layers, to evaluate the total organic carbon based on soil mass, their storage in the soil depth and total organic carbon content in macro, meso and microaggregates. The results showed that in the long term, no-tillage system stored 1.5 Mg ha-1 total organic carbon in the surface layer. In the conventional management, the balance was negative, soil lost around 1.0 Mg ha-1 of organic carbon. There was no recovery of carbon in the deeper layers of all evaluated systems. The content of total organic carbon in aggregates varied with the size and form of adopted management, with higher accumulation in macroaggregates.

http://www.scielo.br/pdf/rbeaa/v16n10/a04.pdf

Estoque de carbono no solo e agregados em Argissolo sob diferentes manejos de longa duração

Spatial assessment of soil erosion is essential for the adaptation of agricultural practices and monitoring of soil losses. In this sense, this study aims to assess the efficiency of magnetic susceptibility (MS) as a predictor of soil erodibility factors (K for USLE model; Ki and Kr for WEPP model) fora detailed mapping of Oxisols with different iron contents in northeastern Sao Paulo State, Brazil. This study was carried out in an area of 380 hectares under sugarcane cultivation in Sao Paulo State. Soil samples were collected in a sampling grid (150) and in a transect (86) and physical and chemical analyses and calculations of the erodibility factors/parameters K, Ki, and Kr were performed. Pedotransfer functions (PTFs) were calibrated using simple linear regression analysis to predict the factors/parameters K and Ki using MS as a predictor variable. The observed values of MS and the predicted values of the factors/parameters K, Ki, and Kr were submitted to geostatistical analysis for constructing maps. Magnetic susceptibility can be used as a predictor of erodibility factors (K for USLE model; Ki and Kr for WEPP model) for Oxisols with total iron content ranging from 1 to 20% Fe2O3, with a precision of up to 60% and an accuracy of up to 85%. The results can guide future studies on water erosion in a tropical environment using magnetic soil data as an environmental covariate in the modeling process for large areas.

Prediction and mapping of erodibility factors (USLE and WEPP) by magnetic susceptibility in basalt-derived soils in northeastern São Paulo state, Brazil

The aim of this work was to evaluate the effect of mineral and organic fertilization on the soil- water aggregate stability and on the distribution of C, N and P in different classes of aggregates in an Acrisol. The treatments were 0 and 40 m 3 ha -1 per year of organic fertilizer and 0, 250 and 500 kg ha -1 of mineral fertilizer N-P-K of the formula 4-14-8. An area under Atlantic forest was used as reference. Soil samples were collected at 0-10 and 10-20 cm depths. The distribution of aggregates showed the highest values from 4 to 2 mm. In the organic fertilizer treatment, the aggregates 4-2 mm corresponded to 39.7% of the total on the soil. For the aggregates 4-2 and 0.105-0.25 mm, the total organic carbon contents were 17.5 and 36.7% higher in the organic fertilizer treatments. The organic fertilization contributed to values of N and P of 43 and 38.7% (0-10 cm) and 35.4 and 36.8% (10-20 cm), which were higher than the treatments without organic fertilizer. The carbon/nitrogen ratio did not vary among the aggregate classes in the same treatment. However, the carbon/ phosphorus ratio was reduced with the use of organic and mineral fertilizer. The indexes of aggregates stability were positively correlated with the content of total organic carbon in the 4-2 mm.

https://www.scielo.br/pdf/pab/v43n9/17.pdf

Estabilidade de agregados e distribuição de carbono e nutrientes em Argissolo sob adubação orgânica e mineral

The use of no-tillage system (SNT) with cover plants improves soil aggregation. The aim of this study was to evaluate the stability of aggregates in water and carbon distribution in different aggregates class in Oxisol in no-tillage system, Uberaba, MG, Brazil. It was evaluated two areas in SNT: crop of corn + brachiaria and corn + crotalaria. An area adjacent to the savanna was taken as a condition of the original soil. It was collected samples of soil deformability 0-5 and 5-10 cm, soil depths which was evaluated the stability of aggregates stable in water, by means of indices of aggregation: mean weight diameter (MWD) and geometric mean diameter (GMD). It was also evaluated the distribution of the mass of aggregates and carbon per sieve class. It was found that, regardless of depth, the area of savanna showed higher values for DMP, DMG and carbon. Among the cultivated areas, the system of crop corn + brachiaria showed higher values of DMP and carbon of aggregates in detriment of the area corn + crotalaria. These results indicate that the crop in SNT of corn + brachiaria increases soil aggregation and carbon aggregates when compared to the system of corn + crotalaria.

https://dialnet.unirioja.es/descarga/articulo/5022061.pdf

Estabilidade de agregados e distribuição do carbono em Latossolo sob sistema plantio direto em Uberaba, Minas Gerais

Several factors can affect the behavior of soil structure. Amongst them, the organic carbon (OC) content and the content and type of iron oxides present in the soil have been related as the most important. This work is aimed at evaluating soil aggregate behavior regarding to the role of organic carbon, and forms of iron oxides in two soils developed from basalt in subtropical Brazil. Aggregates with size less than 8 mm of an Udorthents and a Paleudult under forest, pasture and conventional tillage of the steep backslope of Sul Riograndense plateau were shaked in water during 0, 30, 60 and 90 minutes. The aggregate distribution in three size classes was measured as well as the content of OC, iron extractable with ditionite-citrate-bicarbonate (Fed) and ammonium oxalate (Feo) in the aggregates. The Udorthents showed greater content of soil OC than Paleodult and the forest soil showed greater content of soil OC than pasture and conventional tillage. The content of Fed and Feo were similar between both soils and uses. The studied soils showed a differentiated degree of aggregate hierarchy (AH). The most stable aggregates (90min of shaking) presented a trend to possess greater content of OC than the less stable ones (0min of shaking). Amongst the variables considered in this study, the content of OC was the attribute that more affects the expression of AH and the action of iron oxides in the aggregation not only depends on its type and amount, but also of the content of soil OC. It was also observed that the most stable aggregates (90min of shaking) tended to present greater content of Fed and smaller content of Feo.

/pdf/carbono-organico-oxidos-de-ferro-e-distribuicao-de-agregados-3drl8abv9o.pdf

Carbono orgânico, óxidos de ferro e distribuição de agregados em dois solos derivados de basalto no Rio Grande do Sul - Brasil

No hemisferio sul, devido a maior interceptacao de radiacao solar e consequentemente maior evapotranspiracao potencial, diferencas quimicas, fisicas e morfologicas nos solos  desenvolvidos nas faces voltadas para o norte em relacao as voltadas para o sul podem surgir nessas faces. O objetivo desse trabalho foi o de verificar diferencas quimicas e fisicas entre solos nas faces norte e sul da regiao de Santa Maria – RS. Foram realizadas analises quimicas (M.O., pH, pH-SMP, Al, Ca, Mg, K, P, H+Al, CTC efetiva e potencial, Al% e V%) e fisicas (DMG, DMP, EA e teor de argila) de solos desenvolvidos nas superficies norte e sul na regiao de Santa Maria, localizada na latitude sul de 29°43′30′′. Os resultados foram interpretados atraves do teste de t de Student e da analise multivariada utilizando o agrupamento nao ponderado de pares e adotada a distância Euclidiana como criterio de semelhanca. Atraves do teste t de Student, nao foi verificada diferenca significativa entre s variaveis analisadas, exceto para estabilidade de agregados. A analise de agrupamento separou as amostras da face norte daquelas da face sul. Assim, ainda que estas diferencas sejam pequenas para justificar praticas agricolas diferenciadas, pode ser interessante considera-las em estudos pedogeneticos mais detalhados.

Exposição solar e propriedades do solo em santa maria – rs

A study was performed in nine swine slaughterhouses of the South of Brazil, responsible for around 40% of total swine slaughtered in this area, with the aim to estimate the economic impact of micobacteriosis for swine producers. The period studied was from January 1997 to December 1999. To do so, forms were filled with mensal informations about total number of swine slaughtered and occurrence of carcasses condemnations for granulomatous lymphadenitis at the slaughter; other form gave informations about the discounts received by producers depending on the carcasses destiny and about the average value of bonus received for carcass typing. The economic impact was 1,5 million of reais in 1997, 4,27 in 1998 and 6,94 in 1999. Each 0.1% of increment in the prevalence of swine tuberculosis condemnations represented a loss of 201 thousand of reais in 1997, 531 in 1998 and 834 in 1999. The implications and possible reasons of these findings were discussed regarding the elaboration of a rational control program.

Epidemiologia e controle das micobacterioses em suínos no sul do Brasil - estimativa do impacto econômico

Nucleophilic Addition of Potassium Alkynyltrifluoroborates to D‐Glucal Mediated by BF3·OEt2: Highly Stereoselective Synthesis of α‐C‐Glycosides.

A case control study was performed to identify the risk factors associated with the occurrence of swine mycobacteriosis in the South Region of Brazil. Thirty three swine herds with more than two tuberculous pigs at slaughter and 66 herds with no evidence of infection were selected. Two control herds were chosen in a maximum of a 5 km ratio distance from each case. All selected herds were scrutinized through a questionnaire based on literature data and local characteristics. The results showed that an increase risk of infection is associated with: herds with ≥25 sows (OR= 4.2; 1.2≥IC95%≤14.5), nursery without partial or completely lath floor (OR=3.6; 1.05≥IC95%≤12.7), and bad quality of hygiene in the time of inquest (OR=2.9; 0.99≥IC95%≤8.3). The implementation of hygiene and disinfection program was suggested as strategy of control, obviously observing the economic aspects and the resistance of the mycobacteria to the environment and livestock disinfectants

Fernando Ferreira

Papers

Carbono orgânico, óxidos de ferro e distribuição de agregados em dois solos derivados de basalto no Rio Grande do Sul - Brasil

Exposição solar e propriedades do solo em santa maria – rs

Epidemiologia e controle das micobacterioses em suínos no sul do Brasil - estimativa do impacto econômico

Nucleophilic Addition of Potassium Alkynyltrifluoroborates to D‐Glucal Mediated by BF3·OEt2: Highly Stereoselective Synthesis of α‐C‐Glycosides.

Identificação dos fatores de risco associados à ocorrência de micobacterioses no sul do brasil - estudo caso-controle