| Popis: |
This study aimed at contributing to the understanding the physiology, structural distribution and management of Napier grass (Pennisetum purpureum Schum.) since its versatility promoted its wide distribution in tropical and subtropical areas of the world. A series of three experiments were developed to determine growth dynamics, sward structure, and forage quality at different physiology ages. In the first study in long established pasture of Napier grass were applied three fertilizer levels of dairy cattle manure and three cutting intervals. A second experiment included two inorganic nitrogen fertilizer levels and two cutting intervals. The third experiment assessed the physiological performance of the pasture applying destructive sampling every 10 days, from 10 to 80 days. The general objective was to adapt the CROPGRO growth model to Napier grass included in the DSSAT program. Model calibration has been based in a review of Napier grass physiology and in experimental data to provide a structural and quantitative framework for describing crop response to environment and management. The Specie (SPE), Cultivars (CUL) and Ecotype (ECO) files were modified, based first on literature information and secondly, on optimisation against field data. Root Square Mean Error (RMSE) values were 42, 26, 16 and 5% for aboveground biomass, stem biomass, leaf number per stem and plant height, respectively. The Index of Agreement (d) for the same variables was 0.9, 0.8, 0.97 and 0.99 respectively. The incorporation of the Napier grass model into the Cropping System Model (CSM)-CROPGRO Version 4.0 framework confirmed that the new crop model has good potential to assess management strategies for optimising forage production of Napier grass. |
