This study attempts to model the effects of meteorological factors in COVID-19 spread in Brazil • High mean temperatures influenced the COVID-19 transmission rate • Intermediate relative humidity influenced the COVID-19 transmission rate • Correlation of meteorological conditions with COVID-19 spread is presented for five Brazilian cities • This study aims to support decisionmakers to avoid deaths by the collapse of health-care systems

Structure represents one of the main soil physical attributes indicators. The soil porous system (SPS) is directly linked to the soil structure. Water retention, movement, root development, gas diffusion and the conditions for all soil biota are related to the SPS. Studies about the influence of tillage systems in the soil structure are important to evaluate their impact in the soil quality. This paper deals with a detailed analysis of changes in the soil structure induced by conventional (CT) and no-tillage (NT) systems. Three different soil depths were studied (0-10, 10-20 and 20-30 cm). Data of the soil water retention curve (SWRC), micromorphologic (impregnated blocks) (2D) and microtomographic (mCT) (3D) analyses were utilized to characterize the SPS. Such analyses enabled the investigation of porous system attributes such as: porosity, pore number and shape, pore size distribution, tortuosity and connectivity. Results from this study show a tri-modal pore size distribution (PSD) at depths 0-10 and 10-20 cm for the soil under CT and a bi-modal PSD for the lower layer (20-30 cm). Regarding the soil under NT, tri-modal PSDs were found at the three depths analyzed. Results based on the micromorphologic analysis (2D) showed that the greatest contribution to areal porosity (AP) is given by pores of round (R) shape for CT (52%: 0-10 cm; 50%: 10-20 cm; 67%: 20-30 cm). Contrary to the results observed for CT, the soil under NT system gave the greatest contribution to AP, for the upper (0-10 cm) and intermediate (10-20 cm) layers, due to the large complex (C) pore types. For the mCT analysis, several types of pores were identified for each soil tillage system. Small differences in the macroporosity (MAP) were observed for the 0-10 and 20-30 cm between CT and NT. A better pore connectivity was found for the 0-10 cm layer under NT. 2016 Elsevier B.V. All rights reserved.

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Zero-tillage (ZT) is being increasingly adopted globally as a conservationist management system due to the environmental and agronomic benefits it provides. However, there remains little information on the tillage effect on soil pore characteristics such as shape, size and distribution, which in turn affect soil physical, chemical and biological processes. X-ray micro Computed Tomography (μCT) facilitates a non-destructive method to assess soil structural properties in three-dimensions. We used X-ray μCT at a resolution of 70 μm to assess and calculate the shape, size and connectivity of the pore network in undisturbed soil samples collected from a long-term experiment (~30 years) under zero tillage (ZT) and conventional tillage (CT) systems in Botucatu, Southeastern Brazil. In both systems, a single, large pore (>1000 mm 3 ) typically contributed to a large proportion of macroporosity, 91% in CT and 97% in ZT. Macroporosity was higher in ZT (19.7%) compared to CT (14.3%). However the average number of pores was almost twice in CT than ZT. The largest contribution in both treatments was from very complex shaped pores, followed by triaxial and acircular shaped. Pore connectivity analysis indicated that the soil under ZT was more connected that the soil under CT. Soil under CT had larger values of tortuosity than ZT in line with the connectivity results. The results from this study indicate that long-term adoption of ZT leads to higher macroporosity and connectivity of pores which is likely to have positive implications for nutrient cycling, root growth, soil gas fluxes and water dynamics.

Soil water content (θ) and bulk density (ρ s ) greatly influence important soil and plant processes, such as water movement, soil compaction, soil aeration, and plant root system development. Spatial and temporal variability of θ and ρ s during different periods of the year and different phases of crops are of fundamental interest. This work involves the characterization of spatial and temporal patterns of θ and ρ s during different climatic periods of year, aiming to verify whether there are significant temporal changes in ρ s at the soil surface layer when submitted to wetting and drying cycles. The field experiment was carried out in a coffee plantation, Rhodic Kandiudalf soil, clayey texture. Using a neutron/gamma surface probe, θ and ρ s were measured meter by meter along a 200 m spatial transect, along an interrow contour line. During the wet period there was no difference of spatial patterns of θ while during the dry period differences were observed, and can be associated to precipitation events. It was also observed that there are ρ s temporal changes at the soil surface along the studied period as a consequence of the in situ wetting and drying cycles. Key words: neutron/gamma surface probe, wetting/drying cycles, spatial and temporal variability PADRÕES ESPACIAL E TEMPORAL DE MUDANÇAS DA UMIDADE E DENSIDADE DO SOLO NO CAMPORESUMO: Umidade (θ) e densidade do solo (ρ s ) influenciam importantes processos no solo e planta tais como: movimento de água, compactação do solo, aeração do solo e desenvolvimento radicular. Baseado neste fato, questões referentes à variabilidade espacial e temporal de θ e ρ s para diferentes períodos do ano e diferentes fases de desenvolvimento da cultura do café tornam-se de extremo interesse. Este trabalho teve como objetivo caracterizar padrões espaciais e temporais de θ e ρ s durante diferentes períodos do ano e verificar se existem mudanças temporais significativas de ρ s na superfície do solo quando submetida a ciclos de umedecimento/secagem. O experimento foi conduzido em campo cultivado com café em um solo classificado como Nitossolo Vermelho Eutrófico. O experimento iniciou-se em maio de 2001 com espaçamento de 1,75 m entre linhas e 0,75 m entre plantas. Medidas de θ e ρ s foram feitas metro a metro ao longo de 200 m usando uma sonda de superfície nêutron/gama. Durante o período úmido não houve padrões de diferença espacial para θ, enquanto que para o período seco o contrário foi observado. Estes padrões podem ser associados a eventos de precipitação alterando a estrutura de correlação espacial para observações adjacentes de θ. Para ρ s existem mudanças temporais na superfície do solo ao longo do período estudado como uma conseqüência dos ciclos de umedecimento/secagem no campo. Palavras-chave: sonda de superfície nêutron/gama, ciclos de umedecimento/secagem, variabilidade espacial e temporal

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