Claudia Pozzi Jantalia

Estoque de carbono e nitrogênio e emissão de N2O em diferentes usos do solo na Mata Atlântica

The objective of this work was to evaluate the impact on soil organic matter dynamics and N2O emission of the substitution of pasture areas by eucaliptus reforestation and secondary forest. The evaluated areas are localized in Cruzeiro municipality, Sao Paulo state, Brazil. The areas presented common soil usage history, and were used, at first, as pasture. Since 1973, part of the area was reserved for regeneration of the secondary forest, another part was planted with eucalyptus, and the remaining was kept as pasture. To quantify the stocks of C, N and in soil and the 13C isotopic abundance in soil organic matter (SOM), samples from these areas were collected until 1-m depth, using three replicates. The emission of N2O was evaluated with static chambers for one year. The three areas did not show significant differences on C and N stocks of the secondary forest and eucalyptus areas, in comparison to the pasture one. Secondary forest and eucalyptus has greater carbon contribution to SOM. Secondary forest and eucalyptus have highest annual losses of N, as N2O.

Emissão de óxido nitroso com a aplicação de dejetos líquidos de suínos em solo sob plantio direto

O objetivo deste trabalho foi comparar as emissoes de oxido nitroso (N2O) para a atmosfera depois da aplicacao de dejetos liquidos de suinos, em plantio direto (PD) e preparo reduzido (PR) do solo. O delineamento experimental utilizado foi o de blocos inteiramente casualizados com cinco repeticoes. Os tratamentos consistiram na aplicacao (40 m3 ha-1), ou nao, de dejetos liquidos em PD e PR. As emissoes de N2O foram medidas in situ depois da aplicacao dos dejetos, por 28 dias. Os fluxos de N2O aumentaram com a aplicacao dos dejetos e, em apenas 20% das avaliacoes realizadas, foram superiores no PD. As emissoes de N2O relacionaram-se com o aumento do espaco poroso ocupado pela agua. Quantidades acumuladas de N na forma de N2O, emitidas em 28 dias, representaram 0,20 e 0,25% do N total aplicado com os dejetos no PD e PR, respectivamente. Os resultados demonstram que a aplicacao de dejetos liquidos de suinos em PD nao aumenta a emissao acumulada de N2O em relacao a aplicacao em PR.

Balanço energético da produção de grãos, carne e biocombustíveis em sistemas especializados e mistos

The objective of this work was to evaluate the energetic efficiency of mixed and specialized production systems of grain and meat, and the energy balance in bioenergy production. Agronomic data from 20-year farming with specialized and mixed agrosystems were used. As specialized agricultural systems, the following ones were evaluated: grass pasture; grass with legume pasture; and continuous grain production under no tillage or conventional plough tillage. As a mixed system, the integrated crop-livestock was evaluated under no tillage or conventional plough tillage. The agricultural activity were considered energy input, while grain yield and meat production the energy output. The agricultural products obtained in mixed systems showed energy balance and total production of renewable energy equivalent to the those yielded by the specialized systems. The energy balance of soybean biofuel showed positive values both in mixed and in specialized systems regardless of the soil tillage managements. Among the analyzed soybean and maize biofuels, the greatest energy balance was observed in maize bioethanol. The biofuels produced in all production systems show a positive energy balance and can be considered energetically sustainable.

Soil nitrous oxide emissions under different management practices in the semiarid region of the Argentinian Pampas

The aim of this study was to analyze the influence of different crop sequences (soybean-corn and soybean–soybean) and tillage systems (no tillage and reduced tillage) on nitrous oxide (N2O) soil emissions under field conditions. The experiment was carried out in Manfredi, Córdoba province, Argentina on an Entic Haplustoll and N2O emissions were measured in the field during a year. N2O fluxes were low during winter, but in late spring it peaked. For fallow, N-NO3-content was the most important variable to explain N2O emissions. For growing period water-filled pores was the main variable explaining N2O emissions. Nitrogen fertilization of corn crop increased N2O-N emissions, whereas no significant differences were found due to the tillage system. Measured annual N2O-N emissions were generally lower than those calculated using the methodology proposed by the Intergovernmental Panel on Climate Change.

Techniques for the Quantification of Plant-Associated Biological Nitrogen Fixation

There are many techniques available for the quantification of plant-associated biological nitrogen fixation (BNF) and they can be divided roughly into those that are applicable in the field and those that are not. This short review will mainly consider the former and we cite key references that should be consulted for further details. The techniques that are rarely applicable in the field include the acetylene-reduction assay, exposure to 15 N2enriched atmospheres and the total N-balance method.

Eficiência agronômica e de recuperação de P de fertilizante fosfatado organomineral granulado produzido com cama de frango em solo arenoso e argiloso

The objective of this work was to evaluate the effect of inoculation with Azospirillum brasilense, associated with N rates and sources, in soil of the Cerrado (Brazilian savanna), on the grain yield of irrigated wheat (Triticum aestivum). The experiment was carried out under a no-tillage system in a Typic Haplustox. The experimental design was randomized complete blocks with four replicates, in a 2x5x2 factorial arrangement: two N sources (urea and urea with NBPT urease inhibitor); five N rates applied as topdressing (0, 50, 100, 150, and 200 kg ha-1); and with or without seed inoculation with A. brasilense. The increase in the N rates positively affected spike length, number of spikelets and of grains per spike, number of spikes per meter, N accumulation in the straw, leaf chlorophyll content, and grain yield of irrigated wheat, regardless of the use of NBPT urease inhibitor with conventional urea. Singly, inoculation with A. brasilense does not affect production components and grain yield, despite the increase in N content in wheat straw. The inoculation with A. brasilense, associated with the application of 140 kg ha-1 N, provides the highest grain yield of irrigated wheat cropped after corn in low-altitude Cerrado.

Row-Crop Production Practices Effects on Greenhouse Gas Emissions

One of the grand challenges facing humankind is meeting projected demands for agricultural products in a world undergoing global climate change. As demands increase for the reliable and environmentally responsible supply of food and fiber, how management is adapted to meet these demands will determine the sustainability and climate change mitigation potential of row-crop production systems. This chapter addresses direct greenhouse gas (GHG) emissions from agricultural soils resulting from row-crop production practices. The chapter is focused on globally dominant grain cropping systems (maize, wheat, rice) and on identifying agronomic management practices that help reduce GHG emissions, increase SOC sequestration, and subsequently improve soil health.