An outline of Paleoproterozoic-Mesoproterozoic crustal evolution of the NW Amazon craton and implications for the Columbia Supercontinent

The Rio Negro Province in the NW Amazon craton is composed of three domains (northeastern, central, and southwestern) in turn separated into several regional terrains, showing main NE-SW and WNW-ESE structures and being composed of high-grade polydeformed basement with 1840–1700 Ma protolith ages. The Northeastern Domain shows basements dominated by high-K calc-alkaline to shoshonitic metagranitoids, orthogneisses, migmatites, augen gneisses, and local A-type leucogneisses (1810–1760 Ma, Cauaburi Complex). In Venezuela, this basement is not widely known, but encompasses the oldest rocks of the province (1840–1820 Ma, San Carlos Metamorphic Terrane). The Southwestern Domain comprises medium- to high-K calc-alkaline orthogneisses (Querari Complex) with an extended compositional range (diorite to granite), NE-trending main foliation, and 1740–1700 Ma protolith ages. The Central Domain comprises peraluminous crustal-derived granites (1520–1480 Ma), supracrustal rocks, paragneisses, and some Cauaburi Complex inliers. The Nd isotope data for the basement rocks indicates mantle sources with decreasing crustal contributions and younger TDM ages from east (2.54–1.96 Ga) to west (1.97–1.82 Ga). The Rio Negro Province is interpreted as an accretionary orogen formed by a long-lived magmatic arc system active during three phases: 1.84–1.82 Ga, 1.81–1.76 Ga (main flare up) and 1.75–1.70 Ga. Later, this arc system was affected by collisional orogenies at ~1500 Ma (Içana Orogeny) and ~1300 Ma (Putumayo Orogeny), as showed by the Ar–Ar step heating plateau ages (biotite, hornblende) and U-Pb SHRIMP ages (zircon, titanite) recording two main metamorphic events at 1520–1480 Ma (medium–high T) and 1400–1310 Ma (low–medium T), with important tectonothermal effects also further east in the Tapajós-Parima Province. Based on similar accretionary histories, the Rio Negro Province has also apparent long-lived connections with Laurentia and Baltica (Transscandinavian Belt), forming the core of the Columbia Supercontinent.</p

Adubação orgânica da batata com esterco e, ou, Crotalaria juncea: I - produtividade vegetal e estoque de nutrientes no solo em longo prazo Organic fertilization of potato with manure and, or, Crotalaria juncea: I - long term plant productivity and soil nutrient stocks

No Agreste paraibano, a batata (Solanum tuberosum L.) é importante cultura comercial, embora seja limitada pela variabilidade e escassez de chuvas e pela baixa fertilidade do solo. O esterco é a principal fonte de nutrientes utilizada para fertilização do solo, porém geralmente não é disponível em quantidade suficiente nas propriedades rurais para suprir a demanda das culturas agrícolas. Como alternativa tem sido recomendada a adubação verde com Crotalaria juncea L. Realizou-se um experimento, de 1996 a 2002, em um Neossolo Regolítico, com o objetivo de quantificar a produtividade da batata e o estoque de nutrientes no solo, após incorporações anuais de esterco e, ou, crotalária. Os tratamentos consistiram de: incorporação da crotalária (C), adição de 15 t ha-1 de esterco caprino (E), incorporação de crotalária + 7,5 t ha-1 de esterco (CE) e testemunha (T). No final do experimento, o tratamento E promoveu aumentos de 73, 45, 221 e 43 % nos teores de N total, P total, P e K extraíveis (Mehlich-1) do solo, respectivamente, em relação à testemunha. Os tratamentos C e CE aumentaram o N total do solo em 76 e 63 %, mas não aumentaram o teor dos outros nutrientes. Os acúmulos médios de massa seca, N, P e K na parte aérea da crotalária nos tratamentos, ao longo dos cinco anos, foram de 3.550, 69, 6 e 55 kg ha-1, respectivamente. As produtividades médias de tubérculos, ao longo dos cinco anos de colheita, foram de 15.204, 12.053, 11.085 e 7.926 kg ha-1 nos tratamentos CE, C, E e T, respectivamente. Apesar de a adição de 15 t ha-1 de esterco ter proporcionado os maiores aumentos nos nutrientes do solo, as maiores produtividades de tubérculos ao longo do período do estudo foram obtidas quando se combinou o plantio e a incorporação de crotalária com a adição de 7,5 t ha-1 de esterco.<br>Potato (Solanum tuberosum L.) is an important cash crop in the semi-arid region of Paraíba, Brazil. However, potato productivity is limited by low soil fertility and the limited and highly variable precipitation pattern of this region. Animal manure is the main nutrient source for soil fertility amelioration, but farm manure available is usually not enough to fertilize crops. A cover crop could decrease the demand for animal manure. The characteristics of Crotalaria (Crotalaria juncea L.) recommend it as green manure. A field experiment was conducted from 1996 to 2002 to quantify the effects of annual organic fertilization with animal manure and/or crotalaria on potato productivity and soil nutrient stocks. Treatments consisted of: crotalaria incorporation (C), goat manure, 15 t ha-1 (E), crotalaria incorporation + goat manure, 7.5 t ha-1 (CE), and control plots (T). At the end of the study period, treatment E increased soil total N, total P and available P and K by 73, 45, 221 and 43 %, compared to the control plots. Treatments C and CE increased soil total N by 76 and 63%, but had no effect on other soil nutrients. Overall 5-year averages of crotalaria aboveground accumulation of dry matter, N, P and K were 3550, 69, 6 and 55 kg ha-1, respectively. Average potato productivities for the 5-year period were 15204, 12053, 11085, and 7926 kg ha-1, for treatments CE, C, E and T, respectively. Despite the significant increases in soil nutrient stocks as a result of the annual manure addition of 15 t ha-1, potato productivity was consistently higher in the combination of crotalaria plus 7.5 t ha-1 manure treatment