Physical fractions of organic matter and mineralizable soil carbon as quality indicators in areas under different forms of use in the Cerrado-Pantanal Ecotone.

Understanding soil organic matter (SOM) dynamics is essential to employ management that contribute to the improvement of soil quality (SQ). The aim of this study was to characterize the SOM and evaluate the emission of mineralizable C (C-CO2) in different management systems. The soil was collected in five managed areas: exposed soil (ES), conventional tillage system (CTS), no-tillage system (NTS), permanent pasture (PP) and sugarcane (SC), in addition to a forest area (NF), in the layers of 0-5, 5-10, and 10-20 cm. Total organic carbon (TOC), physical-granulometric fractionation of SOM were performed, determining the contents and stocks of particulate organic matter (C-POM; StockPOM) and mineral organic matter (C-MOM; StockMOM), in addition to calculating SQ indices. In addition to C-CO2 emissions from the soil. The areas of PP and NTS presented the highest levels of TOC in the surface layer. The highest levels of C-MOM and StockMOM were observed in the PP area, besides higher CSI (carbon stock index), reaching 1.67 in the 10-20 cm layer. The areas of PP and SC were similar to the NF in all layers regarding CMI (carbon management index). In CTS, there were higher peaks in emissions and accumulation of C-CO2. It is evident that the improvements in the SQ in the areas of PP, SC, and NTS caused mainly by the deposition of plant material and by soil revolving not being performed. In the CTS, high emission peaks of C-CO2 show that the lack of conservation management practices contributes to the emission of greenhouse gases.

Phytoliths as indicators of pedogenesis and paleoenvironmental changes in Spodosols of the state of Rio de Janeiro, Brazil.

This study aims to contribute toward a better understanding of the current biodiversity patterns existing in the Atlantic Forest of the state of Rio de Janeiro from a paleo-ecological approach. Three soil profiles, each formed from distinct source materials under varied climate and vegetation conditions were selected from the coastal regions of Rio de Janeiro, Brazil. Soil horizon samples for chemical and physical characterization were collected from 10 cm-interval depths, and the total organic carbon was determined in addition to performing isotype and phytolithic analyses. The phytolithic analysis associated with the isotopic techniques (δ13C) permitted the characterization of three stages of paleo-environmental evolution for the studied soils, presenting valid trends that indicate small variations within the phytosociological structure of the vegetation along a Spodosols line in the studied areas. These stages indicated that the phytolithic assemblage was formed from a vegetation profile containing more trees, adapted to conditions colder than the existing vegetation, although no environmental changes were detected using the isotopic data. The milder temperature conditions may have favored the pedogenetic processes of the spodic B horizon formation as well as the maintenance of the organic matter contained in the soil. This study serves as the first draft for the paleo-environmental association among the regions where the analyzed profiles are found.

Absorção de nitrogênio pelo algodoeiro herbáceo em dois sistemas de cultivo / Nitrogen uptake by cotton plant in two tillage system

O estudo da marcha de absorção de nutrientes é de fundamental importância para a nutrição de plantas, visto que além de informar a época (estádio fenológico) que está sendo mais absorvido pela cultura, também sinaliza para os níveis de adubação a serem utilizados. Com o objetivo de estabelecer a marcha de absorção de nitrogênio para a cultura do algodão (Gossypium hirsutum L. r. latifolium Hutch.) conduziu-se um experimento num Argissolo Vermelho Amarelo sob delineamento experimental em blocos casualizados sendo dois tratamentos, semeadura convencional, após preparo do solo e semeadura direta sobre a palha da cultura antecessora (milheto), com cinco repetições. As amostragens foram realizadas em função da fenologia e do desenvolvimento das plantas. O acúmulo de massa seca no algodoeiro herbáceo (variedade NuOpal) é linear e crescente até o período de "maçãs", sendo mais intenso com o aparecimento das flores e maçãs, entre 50 e 100 DAE. O teor de nitrogênio é maior em plantas recém emergidas, possuindo picos no inicio do aparecimento dos botões florais e flores, sendo que a partir do aparecimento das "maçãs, o teor de nitrogênio na planta decresce linearmente. A extração de nitrogênio é acentuada a partir do aparecimento das flores (55 a 60 DAE).

The study of nutrient uptake is of fundamental importance to plant nutrition, as well as tell the time (growth stage) being absorbed by the culture, also signals to the levels of fertilizer to be used. Aiming to establish the uptake of nitrogen for cultivation of cotton (Gossypium hirsutum L. r. latifolium Hutch.) led to an experiment in a Alfissol under randomized block design with two treatments, sowing conventional tillage and after tillage on the straw of previous crop (millet), with five replicates. Samples were taken according to the phenology and plants development. The dry matter accumulation in cotton is linear and increasing until the period of large boll, being more intense with the appearance of flowers and boll, or 50 to 100 days after emergence. The nitrogen content is higher in newly emerged plants, having peaks at the beginning of the appearance of squares and flowers, and from the appearance of small boll, the nitrogen content in the plant decreases linearly. The extraction of nitrogen is bigger from the appearance of flowers (55-60 days after emergence).