Janaina Braga do Carmo

A source of methane from upland forests in the Brazilian Amazon

We sampled air in the canopy layer of undisturbed upland forests during wet and dry seasons at three sites in the Brazilian Amazon region and found that both methane (CH4) and carbon dioxide (CO2) ...

Emissions of CO2, N2O, and NO in conventional and no-till management practices in Rondônia, Brazil

Efforts to restore productivity of pastures often employ agricultural management regimes involving either tillage or no-tillage options combined with various combinations of fertilizer application, herbicide use and the planting of a cash crop prior to the planting of forage grasses. Here we report on the emissions of CO2, N2O and NO from the initial phases (first 6xa0months) of three treatments in central Rondônia. The treatments were (1) control; (2) conventional tillage followed by planting of forage grass (Brachiaria brizantha) and fertilizer additions; (3) no-tillage/herbicide treatment followed by two plantings, the first being a cash crop of rice followed by forage grass. In treatment 3, the rice was fertilized. Relative to the control, tillage increased CO2 emission by 37% over the first 2xa0months, while the no-tillage/herbicide regime decreased CO2 emissions by 7% over the same period. The cumulative N2O emissions over the first 2xa0months from the tillage regime (0.94xa0kg N ha–1) were much higher than the N2O releases from either the no-tillage/herbicide regime (0.64xa0kg N ha–1) or the control treatment (0.04xa0kg N ha–1). The highest levels of N2O fluxes from both management regimes were observed following N fertilizations. The cumulative NO releases over the first 2xa0months were largest in the tillage treatment (0.98xa0kg N ha–1), intermediate in the no-tillage treatment (0.72xa0kg N ha–1), and smallest in the control treatment (0.12xa0kg N ha–1). For the first week following fertilization the percentage of fertilizer N lost as N2O plus NO was 1.0% for the tillage treatment and 3.0% for the no-tillage treatment.

Florestas de restinga e de terras baixas na planície costeira do sudeste do Brasil: vegetação e heterogeneidade ambiental

Foram avaliadas semelhancas floristicas entre duas fisionomias de Floresta Atlântica na regiao costeira do Brasil, denominadas Floresta de Restinga e Floresta das Terras Baixas. A hipotese era que, devido a diferenca nos processos geomorfologicos, essas duas florestas difeririam em variaveis fisico-quimicas dos solos, composicao floristica, biomassa aerea e producao de serapilheira. O trabalho foi conduzido em uma area de 1 ha (100 × 100 m) em cada tipo de floresta, no municipio de Ubatuba, Sao Paulo. Foram registrados e medidos todos os individuos arboreos com DAP > 4,8 cm e coletadas amostras de solo e serapilheira. As analises de agrupamento e de ordenacao indicaram que os solos e principalmente a floraxa0distribuem-se como grupos bem definidos, concordando com a hipotese de distincao entre as duas florestas. A diversidade de especies foi maior (p 0,05) entre as duas florestas. Esse aparente paradoxo poderia ser explicado supondo-se que, uma vez que especies diferentes consigam se estabelecer na Restinga ou nas Terras Baixas e encontrem um espectro favoravel de condicoes e recursos, elas tenderiam a persistir e se desenvolver naquele local; nesse caso, embora as condicoes edaficas difiram entre as duas areas, cada especie responderia de modo particular a essas variacoes, de modo que as florestas poderiam atingir valores semelhantes de biomassa e producao de serapilheira. E provavel que o filtro ambiental condicionado pelos solos esteja sendo importante para a forte separacao floristica entre essas duas florestas.It was evaluated the floristic similarity between two Atlantic Rainforest physiognomies in Brazilian coast area, herein called Restinga and Lowland forests. The hypothesis was that, due the differences in geomorphologic processes, these forests would differ on soil physical and chemical properties, floristic composition, live above-ground biomass and litterfall production. It was sampled 1 ha (100 × 100 m) for each site located in Ubatuba, Sao Paulo state, SE Brazil. Within each hectare it was recorded trees with DBH > 4.8 cm in all 10 × 10 m contiguous plots, and collected soil and litterfall samples. The cluster and ordination analyses indicated the two communities as distinct groups considering soil and floristic composition, agreeing with the initial hypothesis. Species diversity was higher (p 0.05) between the two forests. This apparent paradox could be explained assuming that, since different species establish themselves in the Restinga or Lowland forests and find a favorable spectrum of conditions and resources, they would tend to persist and to develop in that place; even so the edaphic conditions differ between the Restinga and Lowland forests, each species could respond in a particular way to these variations, and then both forests could reach similar values of biomass and litterfall production. It is probable that the environmental filter conditioned by soils has being important for the strong floristic segregation between these two forests.

Sugarcane Crop Residue Increases N2O and CO2 Emissions Under High Soil Moisture Conditions

Sugarcane crop residues from green cane harvests may affect the greenhouse gas fluxes from the soils. Therefore, it is important to understand how changes in soil moisture covered with cane trash alter the N2O and CO2 emission. The aim of this study was to evaluate N2O and CO2 emission from repacked soil columns incubated with (16xa0Mgxa0ha−1) or without crop residues and N fertilizer (0 or 2.1xa0gxa0Nxa0m−2), and as a function of four soil moisture levels (25, 50, 75 and 100xa0% of water holding capacity). For gas samplings, the columns were closed with a lid and four gas samples were taken in 20xa0min. The N2O fluxes increased linearly (pxa0<xa00.01) with increasing soil moisture regardless of the residue application on soil. However in the columns with trash the moisture effect, on N2O emission rates, was two-fold greater. Every 10xa0% increase in moisture in relation to the holding capacity resulted in losses equivalent to 790 and 1,640xa0μgxa0Nxa0m−2 for the 0 and 16xa0Mgxa0ha−1 crop residue rates, respectively. In conditions of low moisture (25 and 50xa0%), the crop residue did not increase emissions compared to the bare soil. The CO2 emission also was linearly stimulated with increasing soil moisture, regardless of crop residue application. However, the CO2 emission rate was higher with the residue. Our study indicates that the effects of crop residue on greenhouse gas emissions are exacerbated in periods with high soil moisture.

Impactos da aplicação de biossólidos na microbiota de solos tropicais

A aplicacao de biossolidos de Estacoes de Tratamento de Esgotos (ETEs) em solos agricolas e florestais tem sido uma das praticas alternativas preconizadas para a reciclagem desses residuos orgânicos. No entanto, alguns biossolidos de ETEs podem conter metais e, ou, xenobiontes que poderiam afetar a microbiota. Neste trabalho, os impactos da aplicacao de biossolidos das ETEs de Barueri e Franca (SP), com alta e baixa concentracao de metais, respectivamente, na microbiota de um solo argiloso (Nitossolo Vermelho eutroferrico tipico) e um arenoso (Neossolo Quartzarenico ortico tipico) foram determinados em condicoes de microcosmos. Imediatamente apos a adicao de diferentes doses de biossolidos ao solo, e depois de 4, 8, 16, 32 e 64 dias de incubacao, a respiracao basal (RB), C na biomassa microbiana (CB), quociente metabolico (qCO2) e relacao CB/C-orgânico do solo (CB/Corg) foram avaliados. No geral, a RB foi maior nos solos com maiores quantidades de biossolidos, sendo os maiores acrescimos verificados logo apos a aplicacao dos biossolidos. No solo arenoso, decrescimos significativos do CB foram observados nos tratamentos com as doses mais elevadas de biossolidos. O qCO2 foi maior nos solos com doses mais elevadas de biossolidos, mas diminuiu com o aumento do periodo de incubacao. Independentemente do tipo de solo, CB/Corg foi maior nos solos que nao receberam biossolidos, em relacao aos solos que receberam biossolidos ricos em metais. A relacao CB/Corg nos solos tratados com biossolidos ricos em metais diminuiu significativamente entre 4 e 16 dias de incubacao, nao sofrendo alteracoes posteriormente. Esses dados indicam que a aplicacao de biossolidos nos solos analisados, independentemente do teor de metais, pode causar um estresse transiente na comunidade microbiana, dependendo da dose aplicada, e que alteracoes na estrutura das comunidades microbianas podem estar ocorrendo.

Nitrogen dynamics during till and no-till pasture restoration sequences in Rondônia, Brazil

The clearing of tropical rain forest in the Amazon basin has created large areas of cattle pasture that are now declining in productivity. Practices adopted by ranchers to restore productivity to degraded pastures have the potential to alter soil N availability and gaseous N losses from soils. We examined how soil inorganic N pools, net N mineralization and net nitrification rates, nitrification potential and NO and N2O emissions from soils of a degraded pasture responded to the following restoration treatments: (1) soil tillage followed by replanting of grass and fertilization, (2) no-till application of non-selective herbicide, planting of rice, harvest followed by no-till replanting of grass and fertilization, and (3) the same no-till sequence with soybeans instead of rice. Tillage increased soil NH4+ and NO3? pools but NH4+ and NO3? pools remained relatively constant in the control and no-till treatments. Cumulative rates of net N mineralization and net nitrification during the first 6xa0months after treatment varied widely but were hightest in the tilled treatment. Emissions of NO and N2O fluxes increased with tillage and with N fertilization. There were no clear relationships among rates of N fertilizer application, net N mineralization, net nitrification, NO, N2O and total N oxide emissions. Our results indicate that pasture restoration sequences involving tilling and fertilizing will increase emissions of N oxides, but the magnitude of the increase is likely to differ based on timing of fertilizer application relative to the presence of plants and the magnitude of plant N demand. Emissions of N oxides appear to be decreased by the use of restoration sequences that minimize reductions in pasture grass cover.

Diurnal changes in nitric oxide emissions from conventional tillage and pasture sites in the Amazon Basin: influence of soil temperature

We have investigated a subset of restoration practices applied to a degraded pasture at Fazenda Nova Vida, a 22000 ha cattle ranch in Rond^onia, Brazil. Nitric oxide (NO) and carbon dioxide (CO2) emissions from soils were measured in conventional tillage and current pasture sites to assess N and C losses. Mean daily NO emissions from tilled plots were at least twice those from the pasture. Nitric oxide emissions from the tilled sites showed a strong diurnal pattern, while those from the pasture sites did not. Mean daytime NO emissions from the tilled sites were 9.7xa0μg NO-Nxa0m−2 h−1, while mean nighttime emissions were 29.7xa0μg NO-Nxa0m−2 h−1. In the pasture sites, NO emissions were 7.6xa0μg NO-Nxa0m−2 h−1 during the day, and 7.7xa0μg NO-Nxa0m−2 h−1 at night. Surface soil temperature was a good inverse predictor (r2=0.75) of NO emissions from the tilled sites. Carbon dioxide emissions from the tilled sites were generally larger than CO2 emissions from the pasture sites. The mean CO2 emission rate from the tilled sites was 179xa0mg Cxa0m−2 h−1, while it was 123xa0mg Cxa0m−2 h−1 from the pasture sites. There was no distinct diurnal pattern for CO2 emissions. We found that the very high temperatures measured at the soil surface in the tillage plots, in the range of 40–45°C, reduced the rate of NO emission. The reduction in NO emissions may be because of the sensitivity of autotrophic nitrifiers to high temperatures. This study provides insights on how land-use change may alter regional NO fluxes by exposing certain microbial communities to extreme environmental conditions. Future studies of NO emissions in tropical agricultural systems where soils are bare for extend periods need to make diurnal measurements or the daily fluxes will be substantially underestimated.

Disponibilidade de nitrogênio e fluxos de N2O a partir de solo sob pastagem após aplicação de herbicida

O oxido nitroso (N2O) e um importante gas do efeito estufa, com um alto potencial de provocar o aquecimento global e de vida longa na atmosfera. Grande parte dos fluxos naturais de N2O ocorre a partir dos oceanos, enquanto o restante e resultado principalmente da contribuicao de processos microbiologicos (nitrificacao e desnitrificacao) ocorridos em solos de regioes tropicais. A disponibilidade de N para processos metabolicos dos microrganismos pode ser um importante fator no controle das emissoes de N2O nesses solos. O presente trabalho foi realizado com o objetivo de melhorar a compreensao acerca dos controles sobre os fluxos de N2O a partir de solos com pastagem na Amazonia. Foram investigados os efeitos da disponibilidade de N, C e umidade na emissao de N2O a partir do solo de uma pastagem submetida ou nao a praticas para recuperacao de sua produtividade. O estudo foi realizado em condicoes de laboratorio, incubando o solo coletado nas seguintes situacoes: (a) Controle - solo com pastagem estabelecida em 1983 e com manejo tradicional, constituida de uma mistura de Brachiaria brinzantha e Panicum maximum, alem da presenca de uma variedade de plantas invasoras, e (b) Herbicida - dessecacao total das plantas da pastagem estabelecida em 1983, para o plantio direto de arroz e posterior ressemeadura de braquiaria. E oportuno ressaltar que as amostras de solo (camada de 0-5xa0cm) das areas foram coletadas no terceiro dia apos a aplicacao do agroquimico. Para o estabelecimento das comparacoes e compreensao dos controles nos fluxos de N2O do solo, foram adicionados ao solo para incubacao: nitrato, dextrose e agua; alem do uso de acetileno para bloquear a oxidacao do N2O a N2, estimando, assim, a proporcao de N2 que foi emitido do solo. Os maiores fluxos foram observados quando o nitrato foi acrescentado ao solo sob condicoes de alta umidade. A adicao de dextrose (fonte de C) elevou os fluxos de forma mais intensa no solo que recebeu aplicacao de herbicida, cuja disponibilidade de N tambem era maior. Com a aplicacao de acetileno foi possivel observar que grande parte do N perdido sob formas gasosas ocorre como N2. Desse modo, o processo de desnitrificacao mostrou-se dominante nos fluxos de N2O a partir do solo da pastagem estudada, enquanto o N foi o fator principal no controle desses fluxos.

Nitrogen Dynamics in Forestry and Grassland Soils in the Amazon Region A Review

The main economical land use in the Amazon since the 1970s has been as cattle pastures, which are largely the result of widespread deforestation. Estimates indicate that approximately 120,000 km2 of pastures show some degree of degradation, which will require the opening up of new areas of forest. The authors conclusions are as follows: (1) The quality of organic matter in the forage grasses modifies N cycling in relation to that originally present in forest soils. (2) In cases where N availability in the soil is not limited to the soil microbiological processes, other soil parameters, such as humidity, start to control N2O fluxes to the atmosphere. (3) Tillage and fertilization induce higher nitrate availability in the short term, but this could be synchronized with plant uptake, which would lead to fewer losses from leaching, plus soil denitrification rates would also decrease and would not support N loss in gaseous form. Any degraded pasture recovery strategy that affects available soil N content will also indirectly influence atmospheric N2O flux. When N availability is not a limitation to soil biological processes, water content changes and other soil properties become important N2O flux controllers. (4) If these conditions are acknowledged, there can be a higher level of sustainability and more effective development of the system and productivity can be achieved.

Strategies to mitigate the nitrous oxide emissions from nitrogen fertilizer applied with organic fertilizers in sugarcane

Vinasse is a major byproduct of the sugarcane biofuel industry, recycled in the fields. However, there is evidence that the application of vinasse with mineral nitrogen (N) fertilizers in sugarcane enhances the emission of greenhouse gases (GHGs). Therefore, strategies are needed to decrease the environmental impacts caused by both inputs. We carried out three sugarcane field experiments by applying N fertilizer (ammonium nitrate) with types of vinasses (concentrated-CV and standard-V) in different combinations (vinasses with N fertilizer and vinasses one month before or after mineral N fertilization). The gases nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4) were measured in one experiment fertilized in the beginning (fall/winteru202f=u202fdry season) and two experiments fertilized in the end (springu202f=u202frainy season) of the harvest season. Sugarcane fields were sinks rather than sources of CH4, while total carbon emitted as CO2 was similar between seasons and treatments. The effect of mineral fertilization and vinasses (CV and V) on N2O emissions was highly dependent on soil moisture (rain events). The N2O-N fertilizer emission factor (EF) varied from 0.07% to 0.51%, whereas the average EF of V and CV were 0.66% and 0.34%, respectively. On average across the three experiments, the combination of vinasse (CV or V) with N fertilizer increased the N2O emissions 2.9-fold compared to that of N fertilizer alone. For CVu202f+u202fN, the EF was 0.94% of the applied N and 0.23% of the ammonium nitrate-N, and for Vu202f+u202fN (EFu202f=u202f0.47%), increased emissions were observed in two out of three experiments. The strategy of anticipating or postponing vinasse application by one month with respect to mineral N reduced the N2O emissions by 51% for CV, but not for V. Therefore, to avoid boosting N2O emissions, we suggest applying vinasses (CV and V) before or after mineral N fertilization.