Monitoramento da população de microrganismos amonificadores e nitrificadores e de taxas de amonificação e nitrificação em solos sob cultivo de cana-de-açúcar na região de Ribeirão Preto, SP.

A agricultura intensiva se caracteriza pela mecanização dos processos de produção e pelo uso sistemático de agroquímicos com o objetivo de controlar pragas e doenças e maximizar a produtividade das culturas através da fertilização dos solos. Esta atividade provoca alterações a curto, médio e longo prazos, podendo resultar no comprometimento da qualidade ambiental, além de afetar a disponibilidade dos recursos naturais e a sustentabilidade da atividade agrícola. O conhecimento da estrutura e composição do meio biótico de agroecossistemas sob agricultura intensiva permite o estudo das alterações ambientais resultantes, além do desenvolvimento de práticas direcionadas à reduçao dos impactos e à sustentabilidade da produção agrícola. Foi observado que os solos sob cultivo intensivo da microbacia do Espraiado, em Ribeirão Preto, tem atividade microbiana bastante reduzida quando comparados com solos sob vegetação de mata nativa e de reflorestamento com Eucaliptus (relatório 11.0.94.221.02, SEP, 1995)

Management of nitrogen fertilizer to reduce nitrous oxide (N2O) emission and ammonia (NH3) volatilization from coffee plantation.

Coffee is a key global crop and the second most valuable commodity exported by developing countries, worth around US$19 billion in 2015. Counting with the world\'s largest production of coffee, Brazil is the most important player in the area and in 2016 hit the record, reaching a volume of 51.37 million bags, combining Arabica (43.24 million bags) and Robusta (7.98 million bags). For coffee production, nitrogen (N) fertilization is an important practice because it influences directly the productivity and the coffee quality. However, an efficient N fertilization is important economically and environmentally, aiming a reduction in nutrient losses to the environment, while providing optimal crop yield. The main pathways of N losses from the application of fertilizers are the emission of nitrous oxide (N2O), volatilization of ammonia (NH3), leaching of nitrate (NO3 -) and ammonium (NH4 +). In general, the longer the time the N from fertilizer, organic compounds, crop residues, and etc., are available in the soil for the microbiota and without competition from the uptake by plants, the greater the N2O emission and NH3 volatilization. In this work, evaluations were carried out during the 2015/2016 season with the determination of nitrous oxide (N2O) emission and ammonia volatilization (NH3) from the application of 300 kg N ha-1 fertilizer, in the form calcium nitrate (T2), urea (T5), calcium nitrate + ammonium nitrate (T7) and a control treatment without N (T8)

Emission of greenhouse gases from soils under pastures submitted to diferent grazing managements and nitrogen fertilization rates, and intercropping with macrotyloma.

In Brazil, agriculture contributes to the emission of greenhouse gases, but has great power to sequester carbon (C) in the soil. The objective of this research was to quantify the C stock in the soil due to land use change (LUC) from forest (Atlantic Forest biome) to Urochloa brizantha pasture, obtaining LUC factors; as well as determining C sequestration rates resultant of the adoption of better pasture management practices. The soil C stocks with the change of land use from forest to pasture was investigated in two locations, one with Dystrophic Red Oxisol and Dystrophic Red Argisol, and the other with Dark Red Oxisol, in the cities of Nova Odessa and Pirassununga, both in the State of São Paulo. Soil C stocks were obtained from soil sampling in pits with an auger, in different layers, down to 100 cm deep. The LUC factor was calculated from the ratio between the C stock in the forest soil and the C stock in the soil under pasture, for each location and soil type. The intensification of pasture management was studied in Pirassununga, resultant ofnitrogen fertilization and deferred or rotated grazing, while in Nova Odessa nitrogen fertilization and intercropping between U. brizantha and Macrotyloma axillare were tested. Soil sampling to obtain initial C stocks and after two years of implementing the new management was carried out in a similar way to that mentioned for LUC, but only considering the soil downto 30 cm deep. The factors for LUC varied between 0.76 and 0.98, demonstrating that inadequate management can affect the C stock in the soil in relation to the forest (standard IPCC value of 1), but that these factors increased when an appropriate management was applied, varying between 1.04 and 1.18, when compared to the IPCC factor standard value of 1.17. Furthermore, management practices resulted in C sequestration rates ranging between 1.2 and 4.4 t C ha-1 year-1, relatively high values that demonstrate the high potential of soils under pasture for C sequestration

I costi dell'impero

Il saggio ricostruisce l'evoluzione della perestrojka attraverso il filo conduttore dei rapporti centro-periferia nel blocco socialista, contraddistinti anche negli anni della perestrojka da una attitudine imperiale, decisiva nel determinare l'effetto spillover del nazionalismo e il crollo del blocco

Za poslednie gody sovetsko-ital'janskie otnoshenija poluchili znachitel'noe razvitie

L'articolo esamina l'evoluzione dei rapporti italo-sovietici nell'ambito della distensione