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| Author(s): |
Paola de Figueiredo Bongiovani
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC) |
| Defense date: | 2019-12-06 |
| Examining board members: |
Paulo Cesar Sentelhas;
Eduardo Delgado Assad;
Gil Miguel de Sousa Camara;
Mauricio Antonio Coelho Filho
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| Advisor: | Paulo Cesar Sentelhas |
| Abstract | |
Cassava is one of the most important crops in tropical countries. Due to its tolerance to adverse weather and soil conditions, it has been cultivated as a strategic crop in semi-arid regions. With the predictions of future climate changes, it is imperative to understand in which ways cassava production might be affected in these regions, in order to anticipate crucial actions to prevent and/or attenuate possible impacts and prepare the population to deal with that. In this context, crop simulation models are effective tools to quantify the future climate effect on crop yields. The objectives of this study were: i) to calibrate and evaluate the cassava simulation models DSSAT CSM-CROPSIM-Cassava and CSM-MANIHOT-Cassava to simulate the yields of the BRS Formosa cassava cultivar and analyze the sensitivity of these models; ii) to apply the DSSAT CSM-CROPSIM-Cassava model to determine cassava yields in the Brazilian Semi-arid region (SAB), under actual (1980-2010) and future climate projections, in medium (2040-2070) and long (2070-2100) terms, for intermediate (RCP4.5) and high (RCP8.5) greenhouse gases emissions (GHGs) scenarios, and to elaborate a vulnerability index (IV) for cassava production in the region; iii) to apply the DSSAT CSM-CROPSIM-Cassava model to evaluate potential management strategies, associated to planting dates and irrigation, in order to minimize possible climate impacts, in four locations of SAB. The DSSAT CSM-CROPSIM-Cassava and CSM-MANIHOT-Cassava models presented good performance for simulating Cassava BRS Formosa yields, with mean absolute error (MAE) of 1193 and 1315 kg ha-1, and c index of 0,87 and 0,81, respectively. The ensemble had a better performance than CSM-MANIHOT-Cassava, but worse than CSM-CROPSIM-Cassava, presenting an intermediary MAE, of 1239 kg ha-1, and c index = 0,85. The sensitivity analysis showed that both models are sensitive to variations in mean air temperature and [CO2], in a direct and inverse way, respectively. As for the rainfall, CSM-MANIHOT-Cassava presented low sensitivity, especially for the driest region, whereas CSM-CROPSIM was very responsive. In general, the CSM-CROPSIM model presented higher yield deviations in relation to the variations of air temperature, rainfall and [CO2] than CSM-MANIHOT-Cassava model, being more suitable for evaluation of climate change impacts on cassava yield. The cassava yields were reduced in all future scenarios, reaching -29% for potential yield (PP) and -22% for attainable yield (PA), at the most pessimist one. The PA maps showed that the areas of the regions with lowest yields at the actual scenario (states of PI, CE, PE and BA) tend to remain unchanged at future scenarios, while the ones with the highest yields (Southeast of BA and North of MG) tend to be reduced. The vulnerability of cassava production in SAB to climate change was greater at long term (2070-2100), in both GHGs emission scenarios (RCP4.5 and RCP8.5). A spatial variation of cassava vulnerability to climate change was noticed at SAB, with the most expressive losses occurring at Southwest region (PI, BA and MG states), and the lowest, at North and Northeast. In general, climate change affected negatively the cassava yield in SAB, along with the increase of risk areas for its production in the same region. The strategies for mitigating losses, related to the adjustment of the planting date and use irrigation, showed to be viable for reducing cassava yield losses in SAB in the future climate scenarios. In every assessed location, the default planting date was among the ones that obtained the highest yields, in all scenarios, although some other months presented yield increase in the future climate scenarios under rainfed condition. Under irrigated conditions, the yield levels increased for all scenarios. The highest cassava yield increments were obtained when the crop was irrigated with 6 mm. (AU) | |
| FAPESP's process: | 17/21745-5 - Climate change and its impacts on cassava production in Brazilian semi-arid region and management strategies for mitigation of losses |
| Grantee: | Paola de Figueiredo Bongiovani |
| Support Opportunities: | Scholarships in Brazil - Master |