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Your search keyword '"Fernando Antônio Macena da Silva"' showing total 3 results
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3 results on '"Fernando Antônio Macena da Silva"'

1. Participatory multicriteria assessment of maize cropping systems in the context of family farmers in the Brazilian Cerrado

Author

José Humberto Valadares Xavier, Mário Conill Gomes, Flávio Sacco dos Anjos, Eric Scopel, Fernando Antônio Macena da Silva, and Marc Corbeels

Subjects
conservation agriculture, cropping system, maize, multi-criteria analysis, smallholder farms, Agriculture
Abstract

Conservation agriculture (CA) is recognized as a promising crop management strategy for sustainable agricultural intensification. The objective of this study was to evaluate CA cropping systems for rainfed maize as an alternative to the traditional tillage-based cropping systems (CT) in the context of family farms, using a multi-criteria model that represents the point of view of farmers. Farmers considered several aspects for evaluating the cropping systems, thatwere systematized in the model through five criteria (with sub-criteria): (a) costs; (b) yield; (c) labour; (d) human health and environment; and (e) production risks. CA did not differ from CT for the ‘costs’ criterion but was superior for the ‘yield’ and ‘labour’ criteria. In contrast, CT obtained better ratings for the criteria ‘human health and environment’ and ‘production risks’. Considering all criteria, CA was better appraised than CT. However, a new local policy measure that subsidizes the hiring of mechanized tillage services overturns this outcome, indicating the importance of exogenous factors. Overall, the participatory processes in building the model allowed us to better understand the reasons of adoption or non-adoption of CA by small-scale farmers in the tropics.

Published
2020
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2. Are Soybean Models Ready for Climate Change Food Impact Assessments?

Author

Kritika Kothari, Rafael Battisti, Kenneth J. Boote, Sotirios V. Archontoulis, Adriana Confalone, Julie Constantin, Santiago V. Cuadra, Philippe Debaeke, Babacar Faye, Gerrit Hoogenboom, Qi Jing, Michael van der Laan, Fernando Antônio Macena da Silva, Fabio R. Marin, Alireza Nehbandani, Claas Nendel, Larry C. Purcell, Budong Qian, Alex C. Ruane, and Montserrat Salmerón

Subjects
Meteorology And Climatology, Earth Resources And Remote Sensing
Abstract

An accurate estimation of crop yield under climate change scenarios is essential to quantify our ability to feed a growing population and develop agronomic adaptations to meet future food demand. A coordinated evaluation of yield simulations from process-based eco-physiological models for climate change impact assessment is still missing for soybean, the most widely grown grain legume and the main source of protein in our food chain. In this first soybean multi-model study, we used ten prominent models capable of simulating soybean yield under varying temperature and atmospheric CO2 concentration [CO2] to quantify the uncertainty in soybean yield simulations in response to these factors. Models were first parametrized with high quality measured data from five contrasting environments. We found considerable variability among models in simulated yield responses to increasing temperature and [CO2]. For example, under a + 3 °C temperature rise in our coolest location in Argentina, some models simulated that yield would reduce as much as 24%, while others simulated yield increases up to 29%. In our warmest location in Brazil, the models simulated a yield reduction ranging from a 38% decrease under + 3 °C temperature rise to no effect on yield. Similarly, when increasing [CO2] from 360 to 540 ppm, the models simulated a yield increase that ranged from 6% to 31%. Model calibration did not reduce variability across models but had an unexpected effect on modifying yield responses to temperature for some of the models. The high uncertainty in model responses indicates the limited applicability of individual models for climate change food projections. However, the ensemble mean of simulations across models was an effective tool to reduce the high uncertainty in soybean yield simulations associated with individual models and their parametrization. Ensemble, ensemble mean yield responses to temperature and [CO2] were similar to those reported from the literature. Our study is the first demonstration of the benefits achieved from using an ensemble of grain legume models for climate change food projections, and highlights that further soybean model development with experiments under elevated [CO2] and temperature is needed to reduce the uncertainty from the individual models.

Published
2022
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3. The STICS model simulating soil carbon stocks, soy and maize crop yield and biomass in brazilian savanna under different systems

Author

Victor Roncaratti de Moraes, Osmar Rodrigues Brito ., Fernando Antônio Macena da Silva, and Pedro Rodolfo Siqueira Vendrame

Abstract

O aumento na temperatura mundial média, ocasionado pelo efeito estufa, está relacionado principalmente com as emissões de CO2, sendo que cerca de 20% da emissão brasileira, que é de 1,25 bilhões de toneladas/ano, provém da produção agropecuária. O cerrado representa 24% do território brasileiro e é o segundo maior bioma da América do Sul, superado apenas pela floresta amazônica. Devido à expansão da fronteira agrícola é inevitável que haja degradação progressiva em razão dos cultivos sem adoção de técnicas adequadas de manejo que além de visar a produtividade objetive também conservação ambiental. Todavia, recentes estudos sugerem que a atividade agrícola, por meio da mitigação de carbono pelo solo, é um agente de sequestro de carbono em potencial. Em decorrência deste cenário, torna-se necessário avaliar, quantificar e comparar os diversos sistemas de cultivo com vistas à manutenção ou incremento do carbono orgânico dos solos. Visando selecionar e testar parâmetros de modelagem para simular a dinâmica do carbono no solo de áreas do cerrado brasileiro este estudo foi realizado com o objetivo de utilizar o software de modelagem STICS para simulação do estoque de carbono do solo, produtividade e produção de fitomassa das culturas de milho e soja em áreas do cerrado brasileiro. Foram utilizados dados de estudos prévios realizados pela EMBRAPA-Cerrados em áreas de cultivo submetidas a sistemas de manejo com plantio convencional e plantio direto com as culturas de milho e soja no período 2010-2013. Na primeira etapa procedeu-se a calibração do modelo para estimativas de produtividade e fitomassa em safras de milho e soja, utilizando dados observados pertecentes ao banco de dados da Embrapa-CPAC. Numa segunda etapa efetuou-se simulações da cronossequência (2010-2013) visando avaliar a dinâmica do estoque total de carbono do solo, bem como a produtividade e a produção de fitomassa das culturas de milho e soja cultivadas sob sistemas de manejo com plantio convencional e plantio direto em áreas de cerrado. Na terceira etapa foram feitas análises estatíticas para aferição da qualidade e precisão das simulações via STICS. O modelo STICS não simulou com qualidade e precisão suficientemente altas a produtividade e a produção de fitomassa das culturas de milho (BRS 1030 e PL 1335) e soja (Valiosa), bem como o estoque total de carbono do solo das duas áreas do Cerrado, porém apresentou potencial como ferramenta para estudos com amostragem maior e de maior duração. Os estoques de carbono total do solo do cerrado, no curto período avaliado (2010-2013), não apresentaram variações significativas. Entretanto, é significativamente maior nas camadas superiores (0-5 e 5-10 cm), principalmente nas áreas manejadas sob sistema de plantio convecional. Climate change and constantly raising global temperatures are directly associated with greenhouse effect, which itself is caused mainly by CO2 discharge into the atmosphere. Brazilian emissions sum up to 1.25 billion Mg/year, and approximately 20% of those emissions are due to the agricultural sector. But still, recent studies show that through the correct soil management, agriculture might change from carbon emitter to mitigator. Faced with these facts, the need to develop and adopt low-carbon-emission crop systems is arisen to reduce environment impact. Due to this demand, comes the urge to evaluate, quantify and compare multiple crop systems in relation to soil carbon levels, establishing modelling parameters to carbon dynamics on savanna soils under different crop systems. Data from previous studies carried out by EMBRAPA Cerrados in cultivation under conventional tillage and the conservative system (No-Till and Livestock Integration) through the years 2009-2013 will be used. In first place, three crops were modelled and calibrated by using data aquired from the studied areas, and hence the 2010-2013 scenario was simulated to verify soil carbon levels, comparing them with the data aquired from previous field experimentsins. The model did not reach expected levels of precision, simulating crop yield, biomass and soil carbon, mostly beacause the brief duration of the analyzed scenario was insufficient to verify variations on observed soil carbon, although a higher amount was observed in upper soil layers (0-5 and 5-10 cm) under conventional tillage. Nevertheless, the STICS model shows great potential as a tool for soil preservation and should be studied furthermore.

Published
2016

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