resumo -A agregação do solo pode representar um parâmetro que relaciona o manejo à qualidade do solo para as terras pretas arqueológicas (TPA). O objetivo do trabalho foi estudar a variabilidade espacial dos agregados e matéria orgânica do solo em terra preta arqueológica sob pastagem. Os dados foram coletados em uma parcela amostral com as dimensões de 80 x 56 m, com espaço entre os pontos de 08 m, e total de 88 pontos amostrais. As amostras de solos foram coletadas nas profundidades 0,0-0,05, 0,05-0,10 e 0,10-0,20 m, para as avaliações: diâmetro médio geométrico (DMG), classe de agregados > 2,00mm, 2-1 mm, índice da estabilidade dos agregados (IEA) e matéria orgânica do solo (MO); após análise exploratória e geoestatística, os modelos foram ajustados aos semivariogramas para cada atributo. Os resultados mostraram que a porcentagem de agregados na classe > 2,00 mm apresentou valores acima de 80% indicando maior resistência à desagregação. Os altos teores de MO no solo influenciaram a formação e estabilização dos agregados do solo. palaVras-chaVe: Estrutura do solo; agrEgação; gEoEstatística.spatial Variability oF soil aggregates and soil organic matter in archaeological black earth under pasture abstract -The soil aggregation may represent a parameter that relates handling to soil quality for archaeological black earth (TPA). The objective was to study the spatial variability of the aggregates and soil organic matter in archaeological black earth under pasture. The data were collected in a sample plot with dimensions of 80 x 56 m, with space between the points of 08 m, and total of 88 sampling points. Soil samples were collected at depths 0.0-0.05, 0.05-0.10 and 0.10 to 20 m, for evaluations: geometric mean diameter (GMD), aggregate class > 2,00mm, 2-1 mm, the aggregate stability index (ESI) and soil organic matter (SOM); after exploratory and geostatistical analysis, the models were fitted to semivariograms for each attribute. The results showed that the percentage of aggregates in the class > 2.00 mm had values above 80%, indicating greater resistance to breakdown. The high SOM content in the soil influenced the formation and stabilization of soil aggregates. keywords: soil structurE; aggrEgation; gEostatistics.Variabilidad espacial de la estabilidad de agregados y materia orgánica del suelo en tierra negra arqueológica baJo pastoreo resumen -La agregación del suelo puede representar un parámetro que relaciona el manejo con la calidad del suelo para la tierra negra arqueológica (TNA). El objetivo de este estudio fue investigar la variabilidad espacial de los agregados

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The conversion of forested areas into cropping systems modifies the soil physical attributes and affects the environmental and economic sustainability of agricultural activity. Thus, this work aimed to evaluate the modifications caused in the physical attributes of the soil in the area of guarana, cupuacu, and annatto compared with forest area in southern Amazonas. In the areas of forest and guarana meshes of 90 m × 70 m and regular spacing between the sampling points of 10 m × 10 m, in the area of annatto meshes of 90 m × 56 m and spacing of 10 m × 8 m, for cupuacu meshes of 54 m × 42 m, with spacing between the sampling points of 6 m × 6 m. The samples were collected in the depths of 0.00–0.05, 0.05–0.10, and 0.10–0.20 m, with 80 sampling points in each area, making 960 samples in the four areas. The cupuacu area most closely resembled the most diverse aspects of soil physical attributes with the forest area, and this was noticeable through the averaging test along with the principal component analysis, thus indicating that this crop is the least harmful to the studied soil, as well as the adopted systems of cultivation cause modifications mostly superficially, being these modifications little noticeable in layers superior to 10 cm.

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In the Amazon region, soil patches with an anthropic A horizon are found, called Indian black earths (IBEs). Indian black earths are highly fertile and, therefore, are deforested by small local farmers to cultivate without basic management that maintains soil and crop sustainability. Therefore, in order to evaluate the effect of using different cultures on the spatial variability of soil chemical attributes, three cultivated IBEs and one IBE under natural forest were selected for georeferencing and sample collection. The collection was made with a mesh system with 88 points per IBE, stratified in three layers

The soils of the Amazon region, despite being under one of the densest forests in the world, are mostly characterized by low nutrient availability, with litter being the main nutrient input route. The present work aimed to evaluate the litter decomposition in forest, Cerrado and Cerradão environments in the Amazon. The litter decomposition rate was estimated by mass loss analysis using litter bags. The collections were performed at intervals of 30, 60, 90, 120, 150, 180, 210, 240, 270 and 300 days, with four replications. Once collected, the material contained in each litter bag was placed to dry to obtain the dry mass. And so, the remaining mass percentage, the decomposition rates (k) and the half-life time (t1/2) are estimated. During the studied period, the Cerrado environment presented the lowest constant k (0.0017 g g-1 day-1) and consequently longer half-life (407 days). The monthly deposition in Cerrado input ranged from Mgha-1mother1 (June to September). Among the evaluated environments, the forest presented the highest decomposition speed and Cerrado presented the lowest one. It was evidenced that the decomposition process for all studied environments occurred with greater intensity in the rainy season.

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