ABSTRACT Agroecological management can favor the improvement of soil attributes, especially soil organic matter (SOM) and soil aggregation. The objective of the study was to quantify the carbon contents of the humic and oxidizable fractions of SOM of aggregates from different origins from agroecological management systems. Five experimental areas located in the Integrated Agroecological Production System were evaluated: AFS – Agroforestry System; C-SUN – Coffee in full sun; C-SHA – Shaded coffee; AL-FLE – Cultivation in alleys of Flemingia macrophylla with green beans; and NT – No-tillage. The aggregates were separated, identified, and classified as to their origin or formation pathways into biogenic, intermediate, and physicogenic. The carbon contents of the humic fractions fulvic acid (C-FAF), humic acid (C-HAF) and humin (C-HUMF); and oxidizable fractions (F1 and F2, labile; and F3 and F4, recalcitrant) of SOM were determined. The greatest variations in the carbon values of the humic fractions were observed in the aggregates of the AFS, C-SUN and C-SHA systems. In relation to C-HUMF, the highest contents of this fraction were quantified in the biogenic and intermediate aggregates of the C-SUN, C-SHA and AL-FLE systems. The carbon contents of the oxidizable fractions of SOM showed variability between the management systems, mainly for the F1, F2 and F3 fractions in the aggregates under C-SUN and C-SHA. The C-SUN system showed a higher proportion of more humified and recalcitrant fractions of SOM when compared to the C-SHA system. The management practices maids in the agroecological systems of C-SHA, C-SUN and AFS promoted improvements in soil quality.

RESUMO O manejo agroecológico pode favorecer a melhoraria dos atributos do solo, com destaque para a matéria orgânica do solo (MOS) e agregação do solo. O objetivo do estudo foi quantificar os teores de carbono das frações húmicas e oxidáveis da MOS de agregados de diferentes origens de sistemas de manejo agroecológico. Foram avaliadas cinco áreas experimentais localizadas no Sistema Integrado de Produção Agroecológica: SAF – Sistema agroflorestal; C-SOL – Café em pleno sol; C-SOM – Café sombreado; AL-FLE – Cultivo em aleias de flemíngia com vagem; e PD – Plantio direto. Os agregados foram separados, identificados e classificados quanto à sua origem ou vias de formação em biogênicos, intermediários e fisiogênicos. Nestes, foram determinados os teores de carbono das frações ácido fúlvico (C-FAF), ácido húmico (C-FAH) e humina (C-FHUM); e das frações oxidáveis (F1 e F2, frações lábeis; e F3 e F4, frações recalcitrantes). As maiores variações nos valores de carbono das frações húmicas foram verificadas nos agregados sob SAF, C-SOL e C-SOM. Em relação ao C-FHUM, nos agregados biogênicos e intermediários de C -SOL, C-SOM e AL-FLE foram quantificados os maiores teores dessa fração. Os teores de carbono das frações oxidáveis apresentaram variabilidade entre os sistemas de manejo, principalmente para as frações F1, F2 e F3 nos agregados sob C-SOL e C-SOM. No sistema de C-SOL verifica-se maior proporção de frações mais humificadas e recalcitrantes da MOS em comparação à C-SOM. As práticas de manejo empregadas nos sistemas agroecológicos de C-SOM, C-SOL e SAF proporcionaram melhorias na qualidade do solo.

ABSTRACT The use of Precision Agriculture tools and soil attributes has contributed to local agricultural management in the identification of different productive potentials and quality of pastures. The present study aimed to use Precision Agriculture tools to investigate the spatial variability of soil organic matter fractions and soil chemical and physical attributes and to delineate management zones in pasture soils cultivated under tropical conditions. The study was conducted on a hay production farm located in Seropédica, Brazil. Fifty points were collected on a irregular grid and soil samples were taken at depths of 0-0.20 and 0.20-0.40 m and crop productivity was evaluated. Chemical and physical soil organic matter fractionation was performed to obtain data on fulvic acid, humic and humin fractions, mineral-associated and particulate organic carbon, and light organic matter. Geostatistics and multivariate analysis (principal component analysis and k-means clustering) were performed to define the management zones. The results obtained contributed to the division of the pasture area into two regions that can be managed in different ways aiming to increase soil organic matter in a localized manner with the possibility of reducing the use of inputs and directed management that respects the productive potential of the pasture on the farm.

ABSTRACT This study aimed to assess vegetal cover evolution on a river island within the Ecological Station of (EEP), by remote sensing. For this purpose, Normalized Difference Vegetation Indexes were generated for Landsat 1 (1973) and Landsat 5 (1984, 1990, 2000 and 2011) images. Five landscape units were identified in the field: bare soil, Rough savanna, Typical savanna, Forested savanna and Evergreen dry woods. Only Forested savanna and Evergreen dry woods showed poor spectral splitting, being thus considered as a forestry complex. Changes throughout time have occurred in all units, with decreasing in bare soil areas (-2.56 ha year−1), Rough savanna (-0.66 ha year−1) and Typical savanna (-0.94 ha year−1) and with an increase in the Forested savanna (5.97 ha year−1). Thus, the method used in this study was effective for sorting and assessing plant cover of the landscape units studied over time.

A queima da palhada nos canaviais deverá ser suprimida no Brasil e, por conseguinte, aumentar a colheita mecanizada devido às mudanças nos sistemas de produção e exigências ambientais. Neste trabalho são sintetizados estudos sobre o manejo da colheita da cana-de-açúcar (crua e queimada) e modificações em atributos de solos de tabuleiro apontando demandas de pesquisa. Em geral, os estudos investigaram atributos na camada arável do solo, ou seja, pouco se avaliou sobre os efeitos da queima nas camadas mais profundas mesmo diante da ocorrência do caráter coeso em solos de tabuleiro, que impõe diferenças no manejo desses solos. Quanto ao tempo de experimentação os trabalhos, em geral de curta duração, não indicaram diferenças nos atributos do solo com a mudança de sistema de colheita, embora indiquem que esses efeitos podem surgir a médio ou a longo prazo. Os atributos químicos foram os mais estudados, seguidos dos biológicos e físicos cujos dados indicam que a colheita sem queima altera positivamente os atributos edáficos e a qualidade do solo porém predominam estudos com colheita manual e, portanto, insuficientes para suprir informações sobre a colheita mecanizada e sem queima da palhada, nos solos de tabuleiro.

The practice of burning the sugarcane straw in Brazilian plantations has to be eliminated, which will increase the usage of mechanical harvesting, owing to changes in the production systems and the environmental demands. In this paper studies about the influence of cane harvesting management (green and burnt cane) in the attributes of Tableland soils are resumed, also pointing to research demands. In general, the studies investigated the attributes of the arable layer, i.e., little has been studied about effects of the burning practice in the deeper soil layers, even though Tableland soils show a cohesive character that lead to differences in the soil management. About the experiments duration, the usually short term studies did not show differences in the soil attributes due to changes of the sugarcane harvesting system; though they indicated that these effects could happen in medium or long terms. Chemical soil attributes were the most studied followed by biological and physical. The data acquired indicate that harvesting sugarcane without burning alters positively the soil attributes and the soil quality. However, the studies are generally with manual harvesting and, thus, not sufficient to inform about the effect of mechanized harvesting without burning of sugarcane straw in the Tableland soils.

The aim of this study was to identify, with the use of 31P NMR spectroscopy, organic P species in humic acids (HA) in samples from Oxisol cultivated in chronosequence with sugar cane, pasture and Cerrado. The main forms of P-type found were orthophosphate, monoester-P (phosphate sugars) and P-diester (orthophosphate). The 31P NMR technique proved capable of identifying changes in the areas studied as a function of sugar cane burning time. In areas with 1 and 5 years of burnt cane, a decrease in recalcitrant organic P in humic acids indicated the need for use of P-humic substances for plant nutrition.

Com o objetivo de avaliar os efeitos de diferentes espécies forrageiras e práticas de manejo sobre a variação da fertilidade do solo conduziu-se um experimento no município de Itaperuna, na Região Noroeste do Estado do Rio de Janeiro. Três piquetes de 2 ha foram divididos em um Argissolo Vermelho-Amarelo em relevo forte ondulado, cultivado inicialmente com Brachiaria brizantha. Além da manutenção desta espécie foram implantadas as espécies Tifton 85 (Cynodon spp.) e Suázi (Digitaria swazilandensis) perfazendo três tratamentos que receberam adubação anual a partir da instalação do experimento (2001). Realizaram-se nove coletas de solo em três terços de cada piquete (médio, inferior e superior) entre os meses de abril de 2002 e maio de 2006 e se coletaram amostras de 1 dm³ de solo, em seções de 0,1 até 0,7 m, com duas repetições por trincheira. Foram analisados e interpretados, em cada data de coleta, todos os parâmetros de fertilidade do solo. Os dados demonstraram que, após a introdução das novas espécies, do manejo rotacionado e das adubações de manutenção, os parâmetros de fertilidade mantiveram valores muito próximos sem haver um decréscimo ao longo do tempo na área experimental.

Aiming to evaluate the effects of different grass species and management practices on soil fertility, an experiment was conducted in the municipality of Itaperuna, northwest part of Rio de Janeiro State. Three plots of 2 ha were divided in a Red Yellow Ultisol with a strong ondulating relief originally cultivated with Brachiaria brizantha. Besides the maintenance of this specie, the Tifton 85 (Cynodon spp.) and Suázi (Digitaria swazilandensis) were introduced, performing three treatments which received annual fertilization from the beginning of the experiment (2001). Nine soil samplings were done in three thirds of each plot (medium, inferior and superior) between April 2002 and May 2006. Soil samples of 1 dm³ were taken from 0.1 m to 0.7 m depths, with 2 repetitions per trench. Soil fertility attributes were analyzed and interpreted in each sampling time. The data show that, after the introduction of the new species, the rotationed management and the maintenance fertilization, the soil fertility attributes kept very close values without decreasing along time in the experimental area.

Abstract The study was carried out to evaluate litterfall production in three restoration systems of Atlantic Forest, Poço das Antas biological reserve, Silva Jardim, RJ. The material was collected monthly from November 2000 up to October 2001.The annual litter deposition was 9.69 t ha-1 in dense system, 10.38 t ha-1 in semidense, 9.97 t ha-1 in tradicional system and 12.22 t ha-1 in the secondary forest. There is no significant differences among the models. The values were quite superior to others studies in primary and secondary tropical forests. The leaves fraction were the most representative, with values among 63.1 to 76.2% of the total litter. The deposition was seasonal in the secundary forest and the traditional semi-dense systems, showed closer results to the secondary forest. In relation to nutrient input was observed higher N values than P and K.

Resumo O estudo teve como objetivo avaliar a deposição de serrapilheira e o aporte de nutrientes em três modelos de revegetação e uma área de floresta secundária na Reserva Biológica de Poço das Antas, Silva Jardim (RJ). O material foi coletado mensalmente entre os meses de novembro de 2000 a outubro de 2001. A deposição anual do modelo adensado foi de 9,69 t ha-1, 10,38 t ha-1 no modelo semi-adensado, 9,97 t ha-1 no modelo tradicional, e na mata secundária de 12,22 t ha-1, não havendo diferença significativa entre os modelos, sendo os valores encontrados muito superiores a outros estudos em florestas tropicais. A fração foliar foi a mais representativa com valores entre 63,1 a 76,2%. A deposição foi sazonal nas áreas de floresta secundária e no sistema tradicional semidenso. Em relação ao aporte de nutrientes pode se observar maiores valores de N do que P e K.