Physical Sciences and Mathematics Commons^™

Modelling Basal Area Of Perennial Grasses In Australian Semi-Arid Wooded Grasslands, S. G. Marsden, K. C. Hodgkinson

IGC Proceedings (1997-2023)

In many semi-arid pastoral systems, landscape processes easily become dysfunctional. Shifts to less functional states may be irreversible, and have long-term consequences for pastoral profitability and social viability of rural communities. Typically, shifts to lower functional states involve a decline in perennial grasses (Hodgkinson, 1994). Here we develop a conceptual basis for modelling the basal area of perennial grasses in a semi-arid grassland and validate the model using data from a 10-year grazing study.

A Systems Approach To Assessing The Viability Of Grazing Legume Systems Across Europe, C. F. E. Topp, C. J. Smith, L. Wu, G. Molle

IGC Proceedings (1997-2023)

Forage legumes are important in grassland farming throughout much of the world because of their ability to fix atmospheric nitrogen, and hence they are expected to play an increasingly prominent role in low- input grazing farming systems in Europe. Nevertheless, the socio-economic impact of the adoption of the "new" legume based grazing technologies have been poorly researched (Rochon et al., 2004). Thus a methodology has been developed to:

* Assess the on-farm costs and benefits of including different legume crops for animal production;
* Determine the types of management systems and environmental conditions under which forage legumes may play …

Modelling Tiller Density Dynamics In A Grass Sward, Masahiko Hirata

IGC Proceedings (1997-2023)

Simulation models are useful tools for grassland management. Among many quantitative and qualitative attributes describing vegetation of grasslands, density of plant population is important because of its close relationship with persistence of grasslands (Hirata, 2004), which in turn is crucial for sustainable agricultural production and/or conservation of the environment, wildlife and recreational resource. Although various models have described grassland vegetation, relatively few models have dealt with plant population density. This paper presents a model describing dynamics in tiller population density in a grass sward.

Modelling Winter Grass Growth And Senescence, D. Hennessy, S. Laidlaw, M. O'Donovan, P. French

IGC Proceedings (1997-2023)

In temperate climates, because net grass growth in winter is low, most grass growth models deal with the main growing season (Mar-Oct in the N Hemisphere), with little emphasis on grass growth in winter (Nov-Feb). However, grass tissue turns over continuously (Hennessy et al., 2004) and the fate of herbage entering the winter is important in extended grazing season systems. This study aimed to model winter grass growth for the period 15 Oct 2001 to 28 Jan 2002 for a range of autumn closing dates (1 Sep, 20 Sep and 10 Oct) by modifying an existing model, so that …

Grasscheck: Monitoring And Predicting Grass Production In Northern Ireland, P. D. Barrett, A. S. Laidlaw

IGC Proceedings (1997-2023)

Grass budgeting is a key management practice on dairy farms to balance grass supply on paddocks with grass demand by the grazing herd. Grass budgets must be pre-emptive to be effective. The uncertainty of grass production and the difficulty in quantifying both current and forecasted rates of growth hamper effective budgeting and paddock management. Grass growth rates are highly variable both in time and space. Therefore, they vary greatly between locations at any given time and also across the season at any given location. Figure 1 shows the pattern of growth rates recorded at the Agricultural Research Institute of Northern …

A Simple Theoretical Model For Calculating Agricultural Value Of Grasslands, G. Nagy

IGC Proceedings (1997-2023)

In spite of the emerging new social demands for non-material grassland products and services (nature reservation, environmental protection, landscape and amenity), the productivity of grasslands is going to remain in the mainstream of overall grassland use in many regions and countries of the world. Strategic planning of future grassland use in a region needs reliable information on the agricultural value of grasslands. The purpose of our research programme was to find a model for calculating the agricultural value of grasslands, in order to assist the classification of grassland productivity for a given area.

Decision Support System For Grassland-Based Sheep Production In The Chilean Patagonia, R. R. Vera, S. Morales, C. Aguilar

IGC Proceedings (1997-2023)

Temporal decision-making in sheep production systems of the Chilean Patagonia is influenced by forage availability in existing paddocks, which in turn is determined by previous use, localisation, climate and soil. Also, production strategies are evolving, with a trend towards fat lamb production, introduction of new breeds and a reduction in the importance of wool production. The objective of this study was to develop an initial version of a spatial empirical simulation model based on extremely limited information, to predict forage growth and sheep production so that decision-makers can assess alternative production strategies.

Comparison Of Methodological Tools In Tropical Soil Carbon Sequestration Field Research, Bram Van Putten, M. C. Amézquita

IGC Proceedings (1997-2023)

Models play a crucial role in studying complex systems like soil Carbon sequestration processes (Hanson et al., 2001). A Carbon sequestration research project is currently under way in pasture and silvopastoral systems of four Tropical American ecosystems. A main research question is the identification of Land Management Systems (LMS) that exhibit optimal soil Carbon sequestration capacity (identification question). Another main issue is the extrapolation of data in space and time (extrapolation question).

Modelling Winter Grass Growth And Senescence, D. Hennessy, S. Laidlaw, M. O'Donovan, P. French

IGC Proceedings (1997-2023)

In temperate climates, because net grass growth in winter is low, most grass growth models deal with the main growing season (Mar-Oct in the N Hemisphere), with little emphasis on grass growth in winter (Nov-Feb). However, grass tissue turns over continuously (Hennessy et al., 2004) and the fate of herbage entering the winter is important in extended grazing season systems. This study aimed to model winter grass growth for the period 15 Oct 2001 to 28 Jan 2002 for a range of autumn closing dates (1 Sep, 20 Sep and 10 Oct) by modifying an existing model, so that …

A New Agro-Meteorological Simulation Model For Predicting Daily Grass Growth Rates Across Ireland, R. P. O. Schulte

IGC Proceedings (1997-2023)

Grass growth rates and herbage yields depend on weather conditions, soil characteristics and grassland management and differ from year to year and from site to site. In the past, grass growth has been predicted using both mechanistic and statistical models. The accuracy of mechanistic models is commonly insufficient for practical application, while statistical models generally apply to one test site only (e.g. Han et al., 2003). In this paper a semi-empirical grass growth model is presented which is numerically accurate, but which can be applied to contrasting sites across Ireland at the same time.

Grasscheck: Monitoring And Predicting Grass Production In Northern Ireland, P. D. Barrett, A. S. Laidlaw

IGC Proceedings (1997-2023)

No abstract provided.

Modelling Of Herbage Intake And Milk Production By Grazing Dairy Cows, Rémy Delagarde, M. O'Donovan

IGC Proceedings (1997-2023)

Key-points

1. Models predicting intake and performance of grazing ruminants from animal, sward, grazing and supplements characteristics are rare, but they are now included in several decision support systems (DSS).

2. An evaluation of the performance and accuracy of published models are rarely undertaken by their authors, but this is proposed in this paper.

3. There is still a need for experimental research but also for the development of generic and dynamic models to predict intake and performance over a wide range of grazing conditions.

Data Curation For Modeling Tall Fescue Biomass Dynamics With Dssat-Csm, M. B. Hanson, P. D. Alderman, T. J. Butler, A. Caldeira Rocateli

IGC Proceedings (1997-2023)

While models for predicting forage production are available to aid management decisions for some forage crops, there is limited research for a yield model designed specifically for tall fescue (Schedonorus arundinaceus). Therefore, our objective was to adapt an existing perennial forage model, the Decision Support System for Agrotechnology Transfer Cropping Systems Model (DSSAT-CSM) for predicting forage biomass of tall fescue in the southern Great Plains. To evaluate model performance, there must first be a high level of data manipulation and cleaning. In this project, a cohesive dataset combining biomass, weather, soil, and management data were structured into DSSAT …