Variação da produtividade do arroz de terras altas influenciados pela seca meteorológica em Goiás.

A seca é um fenômeno meteorológico caracterizado pela falta de precipitação pluvial, que pode causar grandes prejuízos à produção agrícola. O presente trabalho tem como objetivo caracterizar a ocorrência de seca, utilizando o Índice Padronizado de Precipitação (SPI) em cinco microrregiões do estado de Goiás e sua influencia na produtividade de arroz de terras altas. As cinco microrregiões estudadas foram: Anápolis, Ceres, Iporá, Anicuns e Goiânia. A série de dados históricos de precipitação foi disponibilizada pela Agência Nacional de Águas (ANA), coletados em um município pertencente à microrregião analisada. O período de estudo foi de 1975 a 2005. Os dados de produtividade, para o mesmo período foi disponibilizado pela AGROTEC. Os valores do SPI foram caracterizados pela a ocorrência dos eventos de seca, frequência relativa, comparação com os dados de produtividade do arroz de terras altas e o percentual de acerto do índice. Foi possível observar que o SPI não acompanhou totalmente a variação da produtividade do arroz de terras altas. O SPI apresentou percentuais de acerto baixos, em todas as microrregiões, ficando próximo a 51%

Persistence in the zero-temperature dynamics of the QQ-states Potts model on undirected-directed Barab\'asi-Albert networks and Erd\"os-R\'enyi random graphs

The zero-temperature Glauber dynamics is used to investigate the persistence probability $P(t)$ in the Potts model with $Q=3,4,5,7,9,12,24,64, 128$, $256, 512, 1024,4096,16384$,..., $2^{30}$ states on {\it directed} and {\it undirected} Barab\'asi-Albert networks and Erd\"os-R\'enyi random graphs. In this model it is found that $P(t)$ decays exponentially to zero in short times for {\it directed} and {\it undirected} Erd\"os-R\'enyi random graphs. For {\it directed} and {\it undirected} Barab\'asi-Albert networks, in contrast it decays exponentially to a constant value for long times, i.e, $P(\infty)$ is different from zero for all $Q$ values (here studied) from $Q=3,4,5,..., 2^{30}$; this shows "blocking" for all these $Q$ values. Except that for $Q=2^{30}$ in the {\it undirected} case $P(t)$ tends exponentially to zero; this could be just a finite-size effect since in the other "blocking" cases you may have only a few unchanged spins.Comment: 14 pages, 8 figures for IJM

The gathering firestorm in southern Amazonia.

Wildfires, exacerbated by extreme weather events and land use, threaten to change the Amazon from a net carbon sink to a net carbon source. Here, we develop and apply a coupled ecosystem-fire model to quantify how greenhouse gas-driven drying and warming would affect wildfires and associated CO2 emissions in the southern Brazilian Amazon. Regional climate projections suggest that Amazon fire regimes will intensify under both low- and high-emission scenarios. Our results indicate that projected climatic changes will double the area burned by wildfires, affecting up to 16% of the region's forests by 2050. Although these fires could emit as much as 17.0 Pg of CO2 equivalent to the atmosphere, avoiding new deforestation could cut total net fire emissions in half and help prevent fires from escaping into protected areas and indigenous lands. Aggressive efforts to eliminate ignition sources and suppress wildfires will be critical to conserve southern Amazon forests

Selection of Stylosanthes Guianensis for the Cerrados of Brazil

Progenies of intervarietal hybrid stylos (Stylosanthes guianensis var.vulgaris x S.guianensis var.pauciflora) with mid-season maturity date (early-and mid-June), high dry matter and seed yields have been identified at the National Beef Cattle Research Center (CNPGC), Campo Grande, MS, Brazil. Dry matter yields of the best selections were comparable to those of the late-flowering control, cv. Mineirão. Several mid-season hybrids produced 150 to 200 kg/ha of seed-inpod and a single plant selection yielded in excess of 300 kg/ha. The high degree of resistance to anthracnose observed in the advanced generations is attributed to the immense genetic diversity of these heterogeneous populations which restricted the development of this highly variable pathogen. Stability of disease resistance of superior mid-season maturity types and their adaptation to a wider range of ecological situations have yet to be assessed in multilocational trials. Grazing productivity experiments are required to determine animal production and persistency of the selected materials

Development of a Multicross Cultivars of Stylosanthes spp.

A synthetic population, referred to as multicross, has been developed from an interspecific mixture of Stylosanthes capitata and S.macrocephala germplasm. This basic population evolved in a farming situation subject to uncontrolled, continuous, heavy grazing. Natural selection and systematically programmed intercrossing among anthracnose-resistant Venezuelan and Brazilian genotypes of S.capitata have played major roles in the subsequent development of this heterogeneous population. Eight anthracnose-resistant Venezuelan and two Brazilian accessions of S.capitata were introgressed into the basic population. Genetic diversity was further increased by adding seed of four selected accessions of S. macrocephala to the synthetic which had already included three accessions from the basic population. The composite was advanced through five generations of bulk seed production to improve its stability, synchronise harvest maturity, and primarily to facilitate natural intercrossing among S.capitata genotypes. The multicross population displayed anthracnose-resistance in the presence of susceptible, infected accessions in field trials conducted over the years since its initial synthesis in 1990

A symplectic realization of the Volterra lattice

We examine the multiple Hamiltonian structure and construct a symplectic realization of the Volterra model. We rediscover the hierarchy of invariants, Poisson brackets and master symmetries via the use of a recursion operator. The rational Volterra bracket is obtained using a negative recursion operator.Comment: 8 page

Extratos de vermicomposto na germinação e no crscimento inicial da alface romana.

No presente trabalho avaliou-se os efeitos de dois diferentes extratos de vermicomposto (TEA 50% e HUM 25%) e um tipo de lixiciado de vermicomposto (LV 25%) sobre a germinação e crescimento inicial de alface romana.Resumo expandido