Universidade Federal de Santa Maria

About: Universidade Federal de Santa Maria is a education organization based out in Santa Maria, Brazil. It is known for research contribution in the topics: Population & Context (language use). The organization has 21178 authors who have published 35632 publications receiving 371665 citations.

Assessing uncertainties in crop and pasture ensemble model simulations of productivity and N2O emissions

Abstract: Simulation models are extensively used to predict agricultural productivity and greenhouse gas emissions. However, the uncertainties of (reduced) model ensemble simulations have not been assessed systematically for variables affecting food security and climate change mitigation, within multi-species agricultural contexts. We report an international model comparison and benchmarking exercise, showing the potential of multi-model ensembles to predict productivity and nitrous oxide (N2O) emissions for wheat, maize, rice and temperate grasslands. Using a multi-stage modelling protocol, from blind simulations (stage 1) to partial (stages 2 –4) and full calibration (stage 5), 24 process-based biogeochemical models were assessed individually or as an ensemble against long-term experimental data from four temperate grassland and five arable crop rotation sites spanning four continents.Comparisons were performed by reference to the experimental uncertainties of observed yields and N2O emissions. Results showed that across sites and crop/grassland types, 23%–40% of the uncalibrated individual models were within two standard deviations (SD) of observed yields, while 42 (rice) to 96% (grasslands) of the models were within 1 SD of observed N2O emissions. At stage 1, ensembles formed by the three lowest prediction model errors predicted both yields and N2O emissions within experimental uncertainties for 44% and 33% of the crop and grass-land growth cycles, respectively. Partial model calibration (stages 2–4) markedly reduced prediction errors of the full model ensemble E-median for crop grain yields (from 36% at stage 1 down to 4% on average) and grassland productivity (from 44%to 27%) and to a lesser and more variable extent for N2O emissions. Yield-scaled N2O emissions (N2O emissions divided by crop yields) were ranked accurately by three-model ensembles across crop species and field sites. The potential of using process-based model ensembles to predict jointly productivity and N2O emissions at field scale is discussed.

Managing fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), with Bt maize and insecticides in southern Brazil.

Abstract: BACKGROUND Maize plants expressing insecticidal proteins of Bacillus thuringiensis are valuable options for managing fall armyworm (FAW), Spodoptera frugiperda, in Brazil. However, control failures were reported, and therefore insecticides have been used to control this species. Based on these, we evaluated Bt maize and its integration with insecticides against FAW in south Brazil. RESULTS Early-planted Agrisure TL, Herculex, Optimum Intrasect and non-Bt maize plants were severely damaged by FAW and required up to three insecticidal sprays. In contrast, YieldGard VT Pro, YieldGard VT Pro 3, PowerCore, Agrisure Viptera and Agrisure Viptera 3 showed little damage and did not require insecticides. Late-planted Bt maize plants showed significant damage from FAW and required up to four sprays, with the exceptions of Agrisure Viptera and Agrisure Viptera 3. Exalt (first and second sprays); Lannate + Premio (first spray) and Avatar (second spray); and Karate + Match (first spray) and Ampligo (second spray) were the most effective insecticides against FAW larvae in Bt and non-Bt maize. CONCLUSION Maize plants expressing Cry proteins exhibited FAW control failures in south Brazil, necessitating insecticidal sprays. In contrast, Bt maize containing the Vip3Aa20 protein remained effective against FAW. However, regardless of the insecticide used against FAW surviving on Bt maize, grain yields were similar.

Metakaolin-based geopolymers: Relation between formulation, physicochemical properties and efflorescence formation

Abstract: The efflorescence formation in metakaolin-based geopolymers is assessed in this study to provide a better understanding of the effect of the synthesis parameters. Efflorescence formation depends on the physical and chemical properties of geopolymers as well as the environmental exposure conditions. In this study a set of fifteen geopolymers were synthesized using different formulation. An accelerated test of efflorescence development is presented, where the grade of degradation was evaluated by visual observation and correlated to leaching potential, physical properties and microstructural features. The use of soluble silicate in the activator provides a denser and a less permeable matrix. This makes the extraction of free alkalis to the surface more difficult, reducing the extent of alkali leaching and therefore efflorescence. The use of K+ is also effective to reduce visible efflorescence. The efflorescence formation is predicted by the properties of the gel formed which are dependent on the mix proportioning.