Manejo da irrigação e fertilizantes nitrogenados para reduzir a volatilização de amônia

Nitrogen losses by ammonia (NH3) volatilization can be reduced by appropriate irrigation management or by alternative N sources, replacing urea. The objective of this study was to evaluate the efficiency of irrigation management and N source combinations in decreasing NH3 volatilization from an Argissolo Vermelho Distrófico típico cultivated for 28 years with black oat (Avena strigosa) and maize (Zea mays), under no-tillage in the region of Depressão Central, Rio Grande do Sul, Brazil. The experiment was arranged in a randomized block design with split plots with three replications, where the main plots consisted of irrigation systems: no irrigation; irrigation immediately before and irrigation immediately after fertilization. The subplots were treated with different N sources: urea, urea with urease inhibitor and slow-release fertilizer, at an N rate of 180 kg ha-1, broadcast over maize, plus a control treatment without N fertilization. Ammonia volatilization was assessed using semi-open static collectors for 1, 2, 4, 6, and 10 days after N fertilization. In general, more than 90 % of total NH3-N losses occurred until three days after N fertilization, with peaks up to 15.4 kg ha-1 d-1. The irrigation was efficient to reduce NH3 losses only when applied after N fertilization. However, reductions varied according to the N fertilizer, and were higher for urea (67 %) and slightly lower for urea with urease inhibitor (50 %) and slow-release fertilizer (40 %), compared with the mean of the treatments without irrigation and irrigation before fertilization. The use of urea with urease inhibitor instead of urea was only promising under volatilization-favorable conditions (no irrigation or irrigation before N fertilization). Compared to urea, slow-release fertilizer did not reduce ammonia volatilization in any of the rainfed or irrigated treatments.A redução das perdas de nitrogênio pela volatilização de amônia (NH3) pode ser alcançada pelo manejo adequado da irrigação, bem como pelo uso de fontes de N alternativas à ureia comum. A eficiência desses fatores em reduzir a volatilização de NH3 foi avaliada em experimento conduzido num Argissolo Vermelho Distrófico típico cultivado por 28 anos no sistema aveia-preta/milho (inverno/verão) em plantio direto na Depressão Central do RS. O delineamento experimental foi de blocos casualizados com parcelas subdivididas, em três repetições, onde as parcelas principais receberam os tratamentos de irrigação (sem irrigação e irrigação imediatamente antes ou após a adubação), e nas subparcelas foram aplicadas diferentes fontes de N (ureia comum, ureia com inibidor de urease e fertilizante de liberação lenta) na dose de 180 kg ha-1 N, além de um tratamento-controle sem adubação nitrogenada. As avaliações de volatilização de NH3 foram realizadas com coletor semiaberto estático aos um, dois, quatro, seis e 10 dias, após a adubação. Mais de 90 % das perdas totais de NH3 por volatilização ocorreram nos três dias que sucederam a aplicação dos fertilizantes, com picos de até 15,4 kg ha-1 d-1 de N. A irrigação foi eficiente em reduzir a volatilização de NH3 apenas quando aplicada posterior à adubação Essa redução variou em razão do fertilizante nitrogenado, sendo superior quando da aplicação da ureia (67 %) e pouco inferior no caso da ureia com inibidor de urease (50 %) e fertilizante de liberação lenta (40 %), em comparação à média dos tratamentos sem irrigação e com irrigação anterior à adubação. A utilização de ureia com inibidor de urease em substituição à ureia comum apenas evidenciou-se promissora quando em condições propícias à volatilização (sem irrigação ou com irrigação anterior à adubação). Em comparação à ureia comum, o fertilizante de liberação lenta não demonstrou potencial de reduzir volatilização em nenhuma situação avaliada

The beneficial effects of a water-based aerobic exercise session on the blood lipids of women with dyslipidemia are independent of their training status

OBJECTIVES: To evaluate the acute effects of a session of water-based aerobic exercise on the blood lipid levels of women with dyslipidemia and to compare these results according to their training status. METHOD: Fourteen premenopausal women with dyslipidemia, aged 40–50 years, participated in two waterbased aerobic exercise sessions, the first when they were generally sedentary and the second after they were trained with a water-based aerobic training program for 12 weeks. Both experimental sessions were performed using the same protocol, lasted 45 min, and incorporated an interval method, alternating 3 min at a rating of perceived exertion (RPE) of 13 and 2 min at an RPE of 9. Total cholesterol (TC), triglycerides (TG), low-density lipoprotein (LDL), high-density lipoprotein (HDL), and lipoprotein lipase enzyme (LPL) were obtained through venous blood collection before and immediately after each session. A generalized estimating equation method and Bonferroni tests were conducted (with time and training status as factors) for statistical analyses. RESULTS: At enrollment, the mean age of the participants was 46.57 years (95% confidence interval [CI] 44.81– 48.34). The statistical analyses showed a significant time effect for all variables (TC: p=0.008; TG: p=0.012; HDL: po0.001; LPL: po0.001) except for LDL (p=0.307). However, the training status effect was not significant for any variable (TC: p=0.527; TG: p=0.899; HDL: p=0.938; LDL: p=0.522; LPL: p=0.737). These results indicate that the TC and TG levels reduced and the HDL and LPL concentrations increased from pre- to post-session in similar magnitudes in both sedentary and trained women. CONCLUSIONS: A single water-based aerobic exercise session is sufficient and effective to beneficially modify the lipid profile of women with dyslipidemia, regardless of their training status

Early type galaxies have been the predominant morphological class for massive galaxies since only z~1

Present-day massive galaxies are composed mostly of early-type objects. It is unknown whether this was also the case at higher redshifts. In a hierarchical assembling scenario the morphological content of the massive population is expected to change with time from disk-like objects in the early Universe to spheroid-like galaxies at present. In this paper we have probed this theoretical expectation by compiling a large sample of massive (M_{stellar}>10^{11} h_{70}^{-2} M_{Sun}$) galaxies in the redshift interval 0 < z < 3. Our sample of 1082 objects comprises 207 local galaxies selected from SDSS plus 875 objects observed with the HST belonging to the POWIR/DEEP2 and GNS surveys. 639 of our objects have spectroscopic redshifts. Our morphological classification is performed as close as possible to the optical restframe according to the photometric bands available in our observations both quantitatively (using the Sersic index as a morphological proxy) and qualitative (by visual inspection). Using both techniques we find an enormous change on the dominant morphological class with cosmic time. The fraction of early-type galaxies among the massive galaxy population has changed from ~20-30% at z~3 to ~70% at z=0. Early type galaxies have been the predominant morphological class for massive galaxies since only z~1.Comment: 24 pages, 11 figures, 7 tables, MNRAS accepted, acknowledgement adde

Evolution of Massive Galaxy Structural Properties and Sizes via Star Formation In the GOODS NICMOS Survey

We present a study of the resolved star-forming properties of a sample of distant massive M_*>10^11M_solar galaxies in the GOODS NICMOS Survey (GNS). We derive dust corrected UV star formation rates (SFRs) as a function of radius for 45 massive galaxies within the redshift range 1.5<z<3 in order to measure the spatial location of ongoing star formation. We find that the star formation rates present in different regions of a galaxy reflect the already existent stellar mass density, i.e. high density regions have higher star formation rates than lower density regions, on average. This observed star formation is extrapolated in several ways to the present day, and we measure the amount of new stellar mass that is created in individual portions of each galaxy to determine how the stellar mass added via star formation changes the observed stellar mass profile, the Sersic index (n) and effective radius (R_e) over time. We find that these massive galaxies fall into three broad classifications of star formation distribution. These different star formation distributions increase the effective radii over time, which are on average a factor of ~16pm5% larger, with little change in n (average Delta n=-0.9pm0.9) after evolution. We also implement a range of simple stellar migration models into the simulated evolutionary path of these galaxies in order to gauge its effect on the properties of our sample. This yields a larger increase in the evolved R_e than the pure static star formation model, with a maximum average increase of Delta R_e~54pm19%, but with little change in n, Delta n ~-1.1pm1.3. These results are not in agreement with the observed change in the R_e and n between z~2.5 and 0 obtained via various observational studies. We conclude that star formation and stellar migration alone cannot account for the observed change in structural parameters for this galaxy population (abridged).Comment: Accepted by MNRAS 18 pages 8 figure

Boletín meteorológico diario: Número 137 - 2004 Mayo 16

O plantio direto (PD), associado a plantas de cobertura, pode melhorar os atributos químicos e a qualidade do solo, dependendo do tipo de solo. O objetivo da pesquisa foi avaliar o impacto do PD, associado a diferentes sistemas de cultura, durante longo período (~30 anos) sobre os atributos químicos e indicadores de qualidade de um solo de clima subtropical e de um solo de clima temperado (Estudos I e II), e da influência de sistemas de cultura sobre a eficiência da calagem superficial em PD em um solo de clima subtropical (Estudo III). Nos estudos I e II foram avaliados experimentos instalados em 1985 em Eldorado do Sul (Brasil) e em Concord (EUA) cultivados em PD e preparo convencional (PC). No experimento em Eldorado do Sul foram utilizados três sistemas de cultura: aveia (Avena strigosa)/milho (Zea mays) (A/M), ervilhaca (Vicia sativa)/milho (V/M) e aveia+ervilhaca/ milho+caupi (Vigna unguiculata) (AV/MC), em duas doses de N (0 e 180 kg ha-1). O experimento em Concord foi conduzido com dois sistemas de cultura: milho contínuo e milho-soja (Glycine max)], em três doses de N (0, 80 e 160 kg ha-1). O Estudo III foi conduzido em um experimento instalado em 1983 em PD, sendo avaliados atributos químicos relacionados à acidez do solo antes e dois anos após a calagem (5,0 Mg ha-1) em cinco sistemas de cultura: pousio/M (P/M), A/M, AV/M, AV/MC, LL (Lablab purpureus)+M (LLM), com e sem calagem e em duas doses de N (0 e 180 kg ha-1). As práticas de manejo de longa duração influenciaram os atributos químicos do solo, principalmente, na camada de 0 a 10 cm de profundidade, na qual o PD aumentou, em média, 23 % o teor de C orgânico do solo (COS), 30 % o teor de nitrogênio total (NT) e 100 % o teor de P disponível, em relação ao PC, nos dois solos. O COS e o NT aumentaram na ordem A/M<V/M<AV/MC, enquanto que, o pH, o P disponível e a saturação por bases reduziram na ordem A/M>V/M>AV/MC. O COS e o NT não foram influenciados, mas o pH e a saturação por bases aumentaram na rotação milho-soja. O COS aumentou 5% na dose de 160 kg N ha-1 no solo temperado. A adubação nitrogenada reduziu o pH e a saturação por bases nos dois solos, contudo reduziu 30 % o P disponível no solo subtropical, mas aumentou 20 % no solo temperado. O PD aumentou o estoque e o índice de estratificação (IE) do COS e do C orgânico particulado (COP) e o índice de labilidade (IL) nos dois solos. A inclusão de leguminosas aumentou o IE do COS e COP, e o IL em PD. Os sistemas com leguminosas de cobertura de solo aumentaram a acidificação e a saturação por Al3+ e reduziram a saturação por bases, comparado com sistemas exclusivamente de gramíneas. Após dois anos da calagem superficial o pH foi maior que 5,0 e a saturação por Al3+ foi < 4,0 % até 5 cm, independente do sistemas de cultura, porém, a saturação por bases aumentou para > 50 % até 7,5.cm. As práticas de manejo apresentam comportamento similar entre os diferentes solos, e os sistemas de culturas não influenciaram na eficiência da calagem na camada superficial do solo.No-till (NT), associated with cover crops, can improve soil chemical properties and quality, which the magnitude of the effects possibly is dependent of soil type. The objective of this research was to evaluate the impact of NT, associated with different cropping systems, cultivated for long-term (~ 30 years) on soil chemical properties and quality indicators of subtropical soil in Southern Brazil and a temperate soil in Midwest US (Studies I and II), and cropping systems influence on liming efficiency in a subtropical soil under long-term NT (Study III). In Studies I and II were used two long-term experiments installed in 1985 in Eldorado do Sul (Brazil) and Concord (US) carried out under NT and conventional tillage (CT). In Brazil, the experiment was composed by three cropping systems: oat (Avena strigosa) / corn (Zea mays) (O/C), vetch (Vicia sativa)/corn (V/C) and oat+vetch/corn+cowpea (Vigna unguiculata) (OV/CC), with two N rates (0 and 180 kg ha-1). In US, the experiment was conducted with two crop rotations: continuous corn and corn-soybean (Glycine max), with three N rates (0, 80 and 160 kg ha-1). The Study III was conducted in a third experiment under NT and assessed soil chemical attributes related to acidity, before and two years after liming (5.0 Mg ha-1), in five cropping systems: fallow/C (F/C), O/C, OV/C,OV/CC, LL (Lablab purpureus)+C LLM), with and without liming and two N rates (0 and 180 kg ha-1). The long-term management effects on soil chemical properties were confined from 0 to 10 cm depth, in which NT system increased, in average, 23 % of soil organic C (SOC), 30 % of total N (TN), 100 % of available P, compared with CT in subtropical and temperate soil. Subtropical cropping systems increased SOC and TN in the order O/C<V/C<OV/CC, while soil pH, available P and base saturation decreased in the order O/C<V/C<OV/CC. Temperate crop rotation had no effects on SOC and TN, but soil pH and base saturation increased in corn-soybean rotation. Nitrogen fertilization increased 5 % of SOC in the N rate of 160 kg ha-1 in temperate soil. Nitrogen fertilization decreased soil pH and base saturation in both soils, but decreased 30% available P in subtropical soil, but increased 20% in temperate soil. No-till increased SOC and particulate organic C (POC) stocks, SOC and POC stratification ratio (SR) and lability index (LI) in both soils. Legume-based cropping systems increased the SOC and POC SR and LI under NT. Besides, legume-based cropping systems increased soil acidification and Al3+ saturation, and decreased base saturation, compared with grass crops. After two years of superficial liming, soil pH increased to >5.0 and Al3+ saturation decreased to <4.0% up to 5 cm, regardless of cropping systems, and base saturation increased to >50% up to 7.5 cm depth. Long-term management practices have similar behavior in the subtropical and temperate soil, and cropping systems has no influence on liming efficiency in topsoil