Mineralization of sheep manure and its influence on lettuce production

Diversos resíduos orgânicos são utilizados na agricultura sem o adequado conhecimento da sua dinâmica de mineralização. Avaliou-se a mineralização de esterco de ovinos e sua influência na produção de alface. Utilizou-se o delineamento experimental de blocos ao acaso com três repetições. Foram utilizadas 25 t ha-1 como dose de esterco para cada um dos seguintes tratamentos: 1) esterco de ovinos que se alimentaram de feno de mandioca (PAM); 2) esterco de ovinos que se alimentaram de subproduto de ervilha (ERV); 3) esterco de ovinos que se alimentaram de feno de capim coast-cross (FCC); 4) esterco de ovinos que se alimentaram de subproduto de saccharina (SAC) e 5) solo sem aplicação de esterco (testemunha). Foi determinada semanalmente a respiração basal do solo, utilizada como indicador de mineralização da matéria orgânica. A massa fresca de alface foi avaliada como medida de produção. Os tratamentos ERV, FCC e SAC apresentaram ganhos de massa fresca na ordem de 68, 65 e 62% em relação à testemunha e de 43, 39 e 33% em relação ao PAM, respectivamente. A produção menor promovida pelo PAM, em relação às demais, pode ser explicada pela forma de mineralização da matéria orgânica que apresentou elevada respiração microbiana cinco dias após o transplantio, com acentuado declínio, nas medições subseqüentes, ao longo do ciclo da cultura. Os demais tratamentos apresentaram mineralização sincronizada com conseqüente aumento na produção de massa fresca. ____________________________________________________________________________________________________________ ABSTRACTSeveral organic wastes are used in agriculture with no precise knowledge about the mineralization dynamics of these materials. In this study the sheep manure mineralization and its influence on the lettuce production was evaluated. A randomized block design with three replications was used. Five treatments were studied using 25 t ha-1 as dose of manure: 1) sheep manure obtained from animals fed with cassava straw (PAM); 2) sheep manure obtained from animals fed with residue of pea crop (ERV); 3) sheep manure obtained from animals fed with Coast-Cross hay (FCC), 4) sheep manure obtained from animals fed with saccharin residue (SAC) and 5) soil without application of manure (control). Weekly the basal respiration was determined and used as an indicator of organic matter mineralization. Lettuce fresh mass was evaluated as a measure of production. Treatments ERV, FCC and SAC showed superior weight gains of 68, 65 and 62% compared to the control and 43, 39 and 33% compared to MAP, respectively. Lower production promoted by the MAP in relation to the other treatments can be explained by organic matter mineralization that showed a high microbial respiration five days after transplanting, with marked decline in subsequent measurements during the crop cycle. The other systems showed mineralization synchronized with the production increase of lettuce fresh mass

Network model of immune responses reveals key effectors to single and co-infection dynamics by a respiratory bacterium and a gastrointestinal helminth

Co-infections alter the host immune response but how the systemic and local processes at the site of infection interact is still unclear. The majority of studies on co-infections concentrate on one of the infecting species, an immune function or group of cells and often focus on the initial phase of the infection. Here, we used a combination of experiments and mathematical modelling to investigate the network of immune responses against single and co-infections with the respiratory bacterium Bordetella bronchiseptica and the gastrointestinal helminth Trichostrongylus retortaeformis. Our goal was to identify representative mediators and functions that could capture the essence of the host immune response as a whole, and to assess how their relative contribution dynamically changed over time and between single and co-infected individuals. Network-based discrete dynamic models of single infections were built using current knowledge of bacterial and helminth immunology; the two single infection models were combined into a co-infection model that was then verified by our empirical findings. Simulations showed that a T helper cell mediated antibody and neutrophil response led to phagocytosis and clearance of B. bronchiseptica from the lungs. This was consistent in single and co-infection with no significant delay induced by the helminth. In contrast, T. retortaeformis intensity decreased faster when co-infected with the bacterium. Simulations suggested that the robust recruitment of neutrophils in the co-infection, added to the activation of IgG and eosinophil driven reduction of larvae, which also played an important role in single infection, contributed to this fast clearance. Perturbation analysis of the models, through the knockout of individual nodes (immune cells), identified the cells critical to parasite persistence and clearance both in single and co-infections. Our integrated approach captured the within-host immuno-dynamics of bacteria-helminth infection and identified key components that can be crucial for explaining individual variability between single and co-infections in natural populations

Greenhouse gas emission associated with sugar production in southern Brazil

<p>Abstract</p> <p>Background</p> <p>Since sugarcane areas have increased rapidly in Brazil, the contribution of the sugarcane production, and, especially, of the sugarcane harvest system to the greenhouse gas emissions of the country is an issue of national concern. Here we analyze some data characterizing various activities of two sugarcane mills during the harvest period of 2006-2007 and quantify the carbon footprint of sugar production.</p> <p>Results</p> <p>According to our calculations, 241 kg of carbon dioxide equivalent were released to the atmosphere per a ton of sugar produced (2406 kg of carbon dioxide equivalent per a hectare of the cropped area, and 26.5 kg of carbon dioxide equivalent per a ton of sugarcane processed). The major part of the total emission (44%) resulted from residues burning; about 20% resulted from the use of synthetic fertilizers, and about 18% from fossil fuel combustion.</p> <p>Conclusions</p> <p>The results of this study suggest that the most important reduction in greenhouse gas emissions from sugarcane areas could be achieved by switching to a green harvest system, that is, to harvesting without burning.</p

Exoerythrocytic Plasmodium Parasites Secrete a Cysteine Protease Inhibitor Involved in Sporozoite Invasion and Capable of Blocking Cell Death of Host Hepatocytes

Plasmodium parasites must control cysteine protease activity that is critical for hepatocyte invasion by sporozoites, liver stage development, host cell survival and merozoite liberation. Here we show that exoerythrocytic P. berghei parasites express a potent cysteine protease inhibitor (PbICP, P. berghei inhibitor of cysteine proteases). We provide evidence that it has an important function in sporozoite invasion and is capable of blocking hepatocyte cell death. Pre-incubation with specific anti-PbICP antiserum significantly decreased the ability of sporozoites to infect hepatocytes and expression of PbICP in mammalian cells protects them against peroxide- and camptothecin-induced cell death. PbICP is secreted by sporozoites prior to and after hepatocyte invasion, localizes to the parasitophorous vacuole as well as to the parasite cytoplasm in the schizont stage and is released into the host cell cytoplasm at the end of the liver stage. Like its homolog falstatin/PfICP in P. falciparum, PbICP consists of a classical N-terminal signal peptide, a long N-terminal extension region and a chagasin-like C-terminal domain. In exoerythrocytic parasites, PbICP is posttranslationally processed, leading to liberation of the C-terminal chagasin-like domain. Biochemical analysis has revealed that both full-length PbICP and the truncated C-terminal domain are very potent inhibitors of cathepsin L-like host and parasite cysteine proteases. The results presented in this study suggest that the inhibitor plays an important role in sporozoite invasion of host cells and in parasite survival during liver stage development by inhibiting host cell proteases involved in programmed cell death