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Propôs-se, neste trabalho, estudar os efeitos da salinidade da água de irrigação sobre a produção do pinhão-manso (Jatropha curcas L.) após poda realizada aos 396 dias após a semeadura - DAS, em ambiente protegido. A pesquisa foi desenvolvida entre maio de 2008 e janeiro de 2009. A cultura foi conduzida em lisímetros de drenagem (200 L) contendo 230 kg de material de solo, Argissolo Acinzentado, devidamente adubado e corrigido. Testaram-se cinco níveis de condutividade elétrica da água de irrigação - CEa (0,6; 1,2; 1,8; 2,4 e 3,0 dS m-1, a 25 ºC). Empregou-se o delineamento experimental em blocos inteiramente casualizados, com quatro repetições. As plantas foram podadas a 80 cm, ao final do primeiro ciclo de produção. Aos 240 dias após a poda (DAPd), plantas irrigadas com água de 3,0 dS m-1 tiveram o número de cachos reduzido em 93%, o peso médio das cascas, das sementes e dos frutos e número de frutos por planta reduzidos em 97%. Os pesos médios do fruto e da semente foram reduzidos em 67 e 49%, respectivamente. Plantas irrigadas com água de 0,6 dS m-1 e 3,0 dS m-1 produziram 32,03 e 22,5% de óleo, respectivamente.

The worldwide historical carbon (C) losses due to Land Use and Land-Use Change between 1870 and 2014 are estimated at 148 Pg C (1 Pg=1billionton). South America is chosen for this study because its soils contain 10.3% (160 Pg C to 1-m depth) of the soil organic carbon stock of the world soils, it is home to 5.7% (0.419 billion people) of the world population, and accounts for 8.6% of the world food (491milliontons) and 21.0% of meat production (355milliontons of cattle and buffalo). The annual C emissions from fossil fuel combustion and cement production in South America represent only 2.5% (0.25 Pg C) of the total global emissions (9.8 Pg C). However, South America contributes 31.3% (0.34 Pg C) of global annual greenhouse gas emissions (1.1 Pg C) through Land Use and Land Use Change. The potential of South America as a terrestrial C sink for mitigating climate change with adoption of Low-Carbon Agriculture (LCA) strategies based on scenario analysis method is 8.24 Pg C between 2016 and 2050. The annual C offset for 2016 to 2020, 2021 to 2035, and 2036 to 2050 is estimated at 0.08, 0.25, and 0.28 Pg C, respectively, equivalent to offsetting 7.5, 22.2 and 25.2% of the global annual greenhouse gas emissions by Land Use and Land Use Change for each period. Emission offset for LCA activities is estimated at 31.0% by restoration of degraded pasturelands, 25.6% by integrated crop-livestock-forestry-systems, 24.3% by no-till cropping systems, 12.8% by planted commercial forest and forestation, 4.2% by biological N fixation and 2.0% by recycling the industrial organic wastes. The ecosystem carbon payback time for historical C losses from South America through LCA strategies may be 56 to 188years, and the adoption of LCA can also increase food and meat production by 615Mton or 17.6Mtonyear-1 and 56Mton or 1.6Mtonyear-1, respectively, between 2016 and 2050.

Microbial-based indicators of soil quality are believed to be more dynamic than those based on physical and chemical properties. Recent developments in molecular biology based techniques have led to rapid and reliable tools to characterize microbial community structures. We determined the effects of conventional and no-tillage in cropping systems with and without cover crops on bacterial community structure, total organic carbon (TOC) and soil aggregation. Tillage and rotation did not affect TOC from bulk soil. However, TOC was greater in the largest aggregate size class (7.98-19 mm), and had greater mean-weight diameter under no-tillage than under conventional tillage in the 0-5 cm soil layer. Soil bacterial community structure, based on denaturing gradient gel electrophoresis of polymerase chain reaction amplified DNA (PCR/DGGE) using two different genes as biomarkers, 16S rRNA and rpoB genes, indicated different populations in response to cultivation, tillage and depth, but not due to cover cropping. Soil bacterial community structure and meanweight diameter of soil aggregates indicated alterations in soil conditions due to tillage system. (c) 2005 Elsevier B.V. All rights reserved.

Nitrous oxide (N2O) is one of the main gases emitted from soils, and the changes in land use in the Amazon may alter gas emission patterns. The objective of this study was to evaluate the effects of land use, temperature, and nitrogen on N2O emissions in soils in the Amazon. For this, three treatments randomized, with five repetitions, were incubated to quantify N2O emissions: (i) three different land uses (wet rainforest, pasture, and agriculture); (ii) different temperatures (25, 30, 35, and 40 °C); and (iii) different nitrogen additions to the soil (0, 90, 180, and 270 kg of N ha−1). Our results show that land use alters the flux of N2O, with the highest emissions observed in agricultural soils compared to that in forest and pasture areas. The change in soil temperature to 30 °C increased N2O emissions with land use, at which the emission of N2O was higher in the pasture and agriculture soils. Our results showed that the emission of N2O in the soil of the Amazon rainforest was low regardless of the temperature and nitrogen treatment. Therefore, the change in land use alters the resilience of the ecosystem, providing emissions of N2O.

The exploitation of natural resources for agriculture is growing to fulfill the demand for food, which requires the rational use of inputs for sustainable production. Brazilian agricultural production stands out on the international scene. For instance, corn is one of the most exported products in Brazil, which is possible through the planting in the second crop season within a year, called the “off-season”. In addition to being a technique that allows soil conservation, it also reduces the use of inputs and soil tillage. The agricultural production systems require a large amount of energy throughout their processes, mainly through inputs and fuels. Energy flows allow for the identification of the efficiency of the production system and, consequently, its sustainability. Indicators regarding net energy gain per area (Energy balance) and energy profitability (Energy Return on Investment) were applied. The first-season system presented higher energy demand when compared to the second-season system, with a difference of 10.24 GJ ha−1 between the conventional ones and 10.47 GJ ha−1 between the transgenic ones. However, the indicators showed higher energy efficiency in the transgenic off-season corn production, in which the return on energy was 55% higher, and the energy incorporation was 35% lower when compared to conventional first-season corn.

Beef cattle production is an important agricultural activity in Brazil, which influences environmental and resource consumption. This study analyzed greenhouse gas (GHG) emission impacts from 17 farms, representing the Brazil’s productive system and determined possible improvements in the production chain. Methane, nitrous oxide, and carbon dioxide emissions were evaluated using the updated Intergovernmental Panel on Climate Change (IPCC) guidelines for national inventories. The GHG inventory included emissions from animals, feeds, and “cradle-to-farm-gate” operations for animal management. Regression analyses of carbon dioxide equivalent (CO2eq) emissions and productive indices were performed to identify possible GHG emission hotspots. The results varied considerably among the farms. The GHG yield ranged from 8.63 to 50.88 CO2eq kg carcass−1. The productive indices of average daily gain (p < 0.0001), area productivity (p = 0.058), and slaughtering age (p < 0.0001) were positively correlated with GHG yield. However, no correlation was found with the stocking rate (p = 0.21). The production chain could be improved through accurate animal management strategies that reduce the slaughtering age and daily weight gain individually or per area using pasture management and strategic animal supplementation, which could subsequently reduce GHG emissions in beef cattle production.