Navegando por Autor "MARTINS, Paulo Fernando da Silva"

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Acesso aberto (Open Access)
Carbon content in Amazonian Oxisols after forest conversion to pasture
(2009-12) SILVA JÚNIOR, Mário Lopes da; DESJARDINS, Thierry; SARRAZIN, Max; MELO, Vânia Silva de; MARTINS, Paulo Fernando da Silva; SANTOS, Elaine Rodrigues; CARVALHO, Claudio Jose Reis de
Soil plays an important role in the C cycle, and substitution of tropical forest by cultivated land affects C dynamic and stock. This study was developed in an area of expansion of human settlement in the Eastern Amazon, in Itupiranga, State of Pará, to evaluate the effects of native forest conversion to Brachiaria brizantha pasture on C contents of a dystrophic Oxisol. Soil samples were collected in areas of native forest (NF), of 8 to 10 year old secondary forest (SF), 1 to 2 year old SF (P1–2), 5 to 7 year old SF (P5–7), and of 10 to 12 year old SF (P10–12), and from under pastures, in the layers 0–2, 2–5 and 5–10 cm, to evaluate C levels and stocks and carry out separation of OM based on particle size. After deforestation, soil density increased to a depth of 5 cm, with greater increase in older pastures. Variation in C levels was greatest in the top soil layer; C contents increased with increasing pasture age. In the layers 2–5 and 5–10 cm, C content proved to be stable for the types of plant cover evaluated. Highest C concentrations were found in the silt fraction; however, C contents were highest in the clay fraction, independent of the plant cover. An increase in C associated with the sand fraction in the form of little decomposed organic residues was observed in pastures, confirming greater sensitivity of this fraction to change in soil use.
Acesso aberto (Open Access)
Propriedades físicas do solo e sistema radicular do cacaueiro, da pupunheira e do açaizeiro na Amazônia oriental
(Universidade Federal do Pará, 2012-10) MARTINS, Paulo Fernando da Silva; AUGUSTO, Sebastião Geraldo
The knowledge on the relationship between roots of crop plants and soil physical properties is very important. This article evaluates the distribution of the root systems of cocoa, palm peach and açai and their relationships with the soil physical properties. The research was carried out in an alic Yellow Latosol and root and soil samples were obtained from 10 cm to 40 cm depth. The experiment was arranged in a randomized block in the factorial design (four depth soils and three root class), with four replications. The açai root amount is twice of the palm peach and ten times more that of cacao. No difference was verified in the amount of roots of peach between the distances of the plants. The roots were collected in two distances of the plant stem in monolith samples and separated in three diameter class: < 1.0 mm, 1.0-3.0 mm e > 3.0 mm. The roots amount of the three plants was directly correlated with the coarse sand content and inversely correlated with clay content and bulk density. The large pores size was also directly correlated with the amount of cacao and açai roots in the three classes of diameter. The açai showed the most abundant root system and it the greatest number of correlations between the amount of roots and the physical properties of soil involving the three diameter root classes.