ABSTRACT The improvement of carbon (C) accumulation in soils has been one of the main purposes of the conservation systems in agricultural production. This study aimed to assess the long-term effect of conventional tillage (CT) and no-tillage (NT) combined with winter cover crops, black oat and oilseed radish, and fallow on C accumulation and stabilization in a very clayey Oxisol in Southern Brazil. Soil samples were collected in the 0-0.05, 0.05-0.10 and 0.10-0.20 m layers of a 26-year-old experiment. Distribution of size-class aggregates, C stock in aggregates, total C stock, and C stocks in the physical fractions, free particulate organic matter (free-POM), occluded particulate organic matter (occluded-POM) and mineral-associated organic matter (min-OM) were assessed. NT had a higher percentage of macroaggregates and C stock in this size-class, and also higher C stock in bulk soil, free-POM and occluded-POM fractions than CT in 0-0.05 m (Tukey’s test p < 0.05), due to higher input of biomass and minimum soil mobilization in NT. Oat and radish had higher C stock in macroaggregates than fallow in 0.05-0.10 m (Tukey’s test p < 0.05). Radish had the highest C stock in the free-POM (0-0.05 m). Fallow decreased the stabilization of macroaggregates and C accumulation in free-POM, due to the lower C input from aboveground biomass over the years. In conclusion, NT after 26 years improved C accumulation and stabilization, mainly in the superficial layer and in POM fractions, and winter cover crops favored the formation and stability of macroaggregates.

Abstract To accelerate the recovery of degraded environments, it is necessary to use ecological restoration techniques, which require validation according to the ecosystem conditions where are implemented. This work aimed to evaluate soil microbiological attributes under different ecological restoration technologies in a subtropical forest. The study was conducted at UTFPR-DV, southwest of Paraná, in an ecotone between Mixed Ombrophilous Forest and Semideciduous Seasonal Forest and on an Oxisol. In December 2010, a tillage area of at least 17 years old was isolated and the passive restoration, tree planting and nucleation treatments were installed in 40x54 m plots and four replications. In November 2018 the soil was sampled in these plots and in a native forest area as a reference. There were calculated soil organic carbon content (OCC) and microbiological attributes such as microbial biomass N and C (NMIC and CMIC), basal respiration, fungal spore content and the metabolic (qCO2) and microbial quotient (MICq). It can be concluded that nucleation technology can restore soil microbiological attributes but has not yet reached the conditions of a natural environment. Passive restoration is not a good technology for restoring soil microbiological attributes. The higher contents of CMIC, NMIC, OCC, MICq and fungal spores in the soil under native forest compared to ecological restoration technologies indicate that eight years of adoption of these techniques have not yet been enough to fully recover soil microbiological activity.

Apesar da eficiência do tampão SMP na estimativa da acidez do solo, atualmente vêm aumentando as preocupações ambientais devido à presença de p-nitrofenol e cromato de potássio. O objetivo deste trabalho foi testar o método proposto por Sikora (2006) como alternativa ao tampão SMP (Tedesco et al., 1995), que é utilizado para estimar a acidez potencial dos solos da Região Sul do Brasil. O teste foi feito com 21 solos, coletados na Região Sul e no Cerrado. Os valores de acidez potencial real desses solos variaram de 35,95 a 4,02 cmol c kg-1 de solo, refletindo ampla variação de acidez. O tampão Sikora não mimetizou o tampão SMP adaptado utilizado na Região Sul do Brasil, já que o primeiro apresentou baixa capacidade de distinguir entre solos com acidez diferente em razão, provavelmente, da sua alta capacidade-tampão, em comparação com a solução SMP adaptada.

Despite the efficiency of the Shoemaker, McLean, Pratt (SMP) buffer method in estimating soil acidity, the presence of p-nitrophenol and potassium chromate in the solution, both hazardous substances, has caused increasing environmental concerns. The purpose of this study was to test Sikora method (Sikora, 2006) as an alternative to the adapted SMP buffer method, generally used to estimate potential acidity of Southern Brazilian soils. For the test, 21 soils in the South and Cerrado regions of Brazil were sampled. (1) The potential acidity values of these soils range from 35.95 to 4.02 cmol c kg-1 of soil, reflecting a wide acidity variation. The Sikora buffer does not mimic the adapted SMP buffer used in Southern Brazil, since the former has a low ability to distinguish soils with different acidity from each other, probably due to the higher buffer capacity than of the adapted SMP solution.

As aplicações sucessivas de fungicidas cúpricos em videiras podem aumentar o teor de cobre total do solo e modificar a sua distribuição e dessorção no perfil do solo. O trabalho objetivou determinar as formas de cobre e a sua dessorção em solos cultivados com videira e submetidos a sucessivas aplicações de fungicidas cúpricos. Amostras de um solo Neossolo Litólico e Cambissolo Húmico foram coletadas em 2006, nas camadas de 0-20 e 20-40 cm, em um vinhedo com 40 anos, em Bento Gonçalves (RS). Amostras de um solo Neossolo Litólico foram coletadas nas mesmas profundidades, em área de mata natural próxima do vinhedo, e os resultados de análise foram usados como referência. Os solos coletados foram conduzidos ao Laboratório de Química e Fertilidade de Solo da Universidade Federal de Santa Maria, onde foram secos, moídos, passados em peneira de malha de 2 mm, e submetidos ao fracionamento químico do cobre pela metodologia de Tessier et al. (1979) e à cinética de dessorção de cobre com EDTA 0,05 mol L-1, em pH 6,0, conforme proposto por Fangueiro et al. (2005). Os resultados mostram que a aplicação de fungicidas cúpricos em videiras aumenta o teor total e das frações biodisponíveis de cobre do solo, inclusive na camada de 20-40 cm. A maior parte do cobre dos solos cultivados com a videira encontra-se retido na fração mineral, e do solo sob mata natural, na matéria orgânica principalmente. A maior quantidade do Cu, independentemente dos materiais adsorventes nos solos cultivados com videira, é facilmente dessorvível e pode ser considerada em equilíbrio rápido com o cobre da solução.

Successive applications of cupric fungicides to grapevine can increase total copper concentration in the soil and modify its desorption in the soil profile. This study was carried out in 2006 in the soil chemistry and fertility laboratory of the Universidade Federal de Santa Maria to evaluate copper forms and desorption dynamics in Udorthent and Haplumbrept soils (in the layers 0-20 and 20-40 cm) under grapevine for 40 years and under successive applications of cupric fungicides. The soils were collected in the wine valley region of Bento Gonçalves, RS, in Southern Brazil. Udorthent samples were also collected (at 0-20 and 20-40 cm) in a forest near the vineyard and the data used as reference. Soil samples were dried, ground and sieved (2 mm), and copper was fractionated using the Tessier methodology (Tessier et al., 1979) and copper desorption with EDTA 0.05 mol L-1 pH 6.0, using the methodology of Fangueiro (Fangueiro et al., 2005). Results showed that the application of cupric fungicides to grapevine increases total copper and its available fractions, including in the 20-40 cm layer. The major part of copper of the soils cultivated with grapevine is retained in the mineral fraction, whereas under natural forest, organic matter is the main reservoir of the element. The greatest partion of copper, independent of the adsorbent material in the soils growing grapevine, is easily desorbable and can be considered of rapid equilibrium with the copper of the solution.