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| Author(s): |
Leandro Coelho de Araujo
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC) |
| Defense date: | 2012-02-13 |
| Examining board members: |
Patricia Menezes Santos;
Luis Gustavo Barioni;
Valdo Rodrigues Herling;
Carlos Guilherme Silveira Pedreira;
José Ricardo Macedo Pezzopane
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| Advisor: | Patricia Menezes Santos |
| Abstract | |
Two experiments were held simultaneously at Embrapa South-East Cattle Research Center (São Carlos, SP, Brazil, 21°57\'42\"S , 47°50\'28\"W) in 2010-2011 using Panicum maximum cv. Mombaça (Guineagrass). They were differentiated by the presence or absence of irrigation. The randomized complete block design with four replications was used. The treatments were determined by cumulative thermal times during each growth cycles (i.e. 250, 500, 750 and 1000 °C, base temperature = 0 °C). After the last sample time (1000° C) of each cycle, all the plots were uniformly cut up to 0.3 m above the soil surface to begin a new cycle of re-growth and sampling. At every new growth cycle the pasture was fertilized (N-P-K). The variables recorded were the dry matter above-residue, identification of apical meristem at vegetative state or flowering one, calculation of water index (WI) by ratio between real evapotranspitarion to crop evapotranspiration using the direct method (Diviner) or actual evapotranspitarion to potential evapotranspitarion usgin an indirect method (Climatologic). The data sets from the experiments were used to determine the critical values of the main variables that may influence the Guineagrass growth, besides parameterizing and evaluating an agroclimatic degree-day model (DDi); a photo-thermal-units model (PUi); a growth climate index model (GCIi) and one biophysical function model (APSIM-Growth). The results showed that the relative production of Guineagrass decreases linearly with the reduction of the WI. The base temperature was estimated equal to 15.6 ° C and Guineagrass is possibly identified as a short-day plant with a photoperiod critical value close to 11.81 h. All models performed well during the parameterization (R2 from 0.78 to 0.86 and coefficient of variation from 27 to 32.1%), and evaluation (R2 from 0.69 to 0.78; agreement index from 0.88 to 0.93; coefficient of variation from 37.6 to 50.2% and mean bias error from 6 to 470 kg DM ha/cutting). APSIM model was the one that showed a minor error and UF model was the empirical model that provided predicted values closer to the observed. (AU) | |
| FAPESP's process: | 09/00263-6 - Mathematics models to simulate the production pasture seasonal of Panicum maximum cv Tanzania in São Paulo State |
| Grantee: | Leandro Coelho de Araujo |
| Support Opportunities: | Scholarships in Brazil - Doctorate |