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Modelling ruminant grazing systems based on native grasslands. 1. Model description and evaluation of the herbage
A Ruggia1, W A H Rossing2, P Soca3
1Instituto Nacional de Investigación Agropecuaria (INIA), Programa Nacional de Investigación en Producción Familiar, Estación Experimental INIA Las Brujas, Ruta 48 km 10, Canelones, Uruguay; Farming Systems Ecology, Wageningen University and Research, Wageningen, the Netherlands.
This study introduces the PASpALuM model for sustainable grassland livestock farming in the Pampas. The model accurately simulates herbage dynamics, supporting ecological intensification and informed grazing management decisions.
Area of Science:
- Ecology
- Agricultural Science
- Environmental Science
Background:
- Sustainable intensification of grassland livestock farms is crucial for beef production and ecosystem services in the Pampas.
- Existing grazing models struggle with generality and realism in heterogeneous, multispecies systems, limiting their ability to simulate complex farm dynamics.
- The farm-scale PAmpa Sustainable grAzing Livestock Management (PASpALuM) model was developed to address these limitations.
Purpose of the Study:
- To present the PASpALuM model, focusing on its herbage dynamics module.
- To evaluate the accuracy and performance of the PASpALuM herbage dynamics module using experimental and on-farm data.
- To assess the model's suitability for supporting farm-context-specific adjustments and redesign plans for sustainable grazing management.
Main Methods:
- Developed the farm-scale PASpALuM model, utilizing herbage height as the key state variable.
- Evaluated the herbage dynamics module with 2-year experimental and 3-year on-farm datasets under contrasting conditions.
- Performed mean squared deviation decomposition and sensitivity analyses to assess model performance and identify key drivers.
Main Results:
- The PASpALuM herbage dynamics module demonstrated good to very good performance, with modeling efficiency ranging from 0.6 to 0.8.
- RMSE values for herbage accumulation rate, mass, and height were within acceptable ranges for both experimental and on-farm datasets.
- Model performance was stronger in autumn and spring, with error structure dominated by lack of correlation, reflecting natural grassland variability.
Conclusions:
- The PASpALuM model accurately simulates herbage dynamics, providing a valuable framework for quantifying the effects of different management strategies.
- The model's accuracy supports its use in comparing grazing strategies to enhance herbage height and allowance under various climate scenarios.
- PASpALuM can aid seasonal grazing management planning at both farm and policy levels, contributing to sustainable livestock farming in the Pampas region.
