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Full-Text Articles in Physical Sciences and Mathematics
A Herbage Growth Model For Different Types Of Natural Grassland, J. Viégas, M. Duru, P. Cruz, J. P. Theau, P. Ansquer, C. Ducourtieux
A Herbage Growth Model For Different Types Of Natural Grassland, J. Viégas, M. Duru, P. Cruz, J. P. Theau, P. Ansquer, C. Ducourtieux
IGC Proceedings (1997-2023)
The aim of this work was to extend existing growth models established for pure stands to a wide range of grassland communities. For this purpose we built a simple growth model, including sub-models for radiation interception and use. Parameters for the effect of nutrient rates (N, P) and defoliation regimes were based on a plant trait database. Senescence and reproductive processes were particularly considered because of their importance in late spring growth. The model makes it possible to simulate the daily biomass production as a function of both environmental factors and the functional type of the dominant species in the …
Modelling Winter Grass Growth And Senescence, D. Hennessy, S. Laidlaw, M. O'Donovan, P. French
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 …
Software Ppbb_Mx: Potential Productivity Modelling Of Brachiaria Brizantha (Cultivars Marandu And Xaraés), E. R. Detomini, D. Dourado Neto
Software Ppbb_Mx: Potential Productivity Modelling Of Brachiaria Brizantha (Cultivars Marandu And Xaraés), E. R. Detomini, D. Dourado Neto
IGC Proceedings (1997-2023)
Recent improvements in computer capacity and technology allow models to be built to simulate the attributes of many agricultural processes and systems. Although Brachiaria brizantha is the most cultivated tropical grass species in Brazil, there is no single tool to predict its production under optimal conditions. The objective of this paper is to present PPBB_MX software to calibrate and simulate (using a stochastical procedure) the shoot and total biomass potential productivity (output variables) of Brachiaria brizantha as a function of the following input variables: local latitude, season (from cutting date - Julian day), length of regrowth (time, days) and climate …
Potential Climate Change Impacts On Beef Production Systems In Australia, David H. Cobon, K. L. Bell, G. M. Mckeon, J. F. Clewett, S. Crimp
Potential Climate Change Impacts On Beef Production Systems In Australia, David H. Cobon, K. L. Bell, G. M. Mckeon, J. F. Clewett, S. Crimp
IGC Proceedings (1997-2023)
There is increasing evidence suggesting that Australia's climate is changing due to enhanced levels of greenhouse gases and that it will continue to change (Pittock 2003). Climate changes are partly established, however the impact on systems, industries and process are unclear. Industry distribution reflects climatically imposed boundaries and the relative profitability of alternative land use. Climate change may negatively impact some existing industries but create opportunities for others. This study provides an assessment of the likely impacts of plausible climate change on the beef industry in central Queensland.
Yield Progress Of Perennial Ryegrass And Silage Maize - Genetic Gain Or Climate Change?, Antje Herrmann, A. Kornher, Friedhelm Taube
Yield Progress Of Perennial Ryegrass And Silage Maize - Genetic Gain Or Climate Change?, Antje Herrmann, A. Kornher, Friedhelm Taube
IGC Proceedings (1997-2023)
Gains in annual dry matter yield (DMY) from breeding achieved during the last decades are reported to range between 2.5 and 6% per decade for perennial ryegrass (Wilkins & Humphreys, 2003). In contrast, accelerated progress in improving DMY has been achieved for silage maize, varying between 8 and 13% per decade (Lauer et al., 2001). These gains are mainly attributed to (i) genetic yield potential increase, (ii) improved crop management and (iii) increased stress tolerance. The potential impact of climate change on yield progress, however, is disregarded in most studies. The objective of this study therefore was to quantify …
Seasonal Variation Of Taproot Biomass And N Content Of Lucerne Crops Under Contrasting Grazing Frequencies, E. I. Teixeira, D. J. Moot, H. E. Brown, M. Mickelbart
Seasonal Variation Of Taproot Biomass And N Content Of Lucerne Crops Under Contrasting Grazing Frequencies, E. I. Teixeira, D. J. Moot, H. E. Brown, M. Mickelbart
IGC Proceedings (1997-2023)
Taproot nitrogen reserves (TN, kg N/ha) a function of N concentration within taproots (N%) and taproot biomass (TBM) are a major determinant of lucerne (Medicago sativa L.) growth rates after defoliation and in early-spring (Avice et al., 1997b). Several studies have shown that N% changes with seasons (Cunninghan & Volenec, 1998) and defoliation frequencies (Avice et al., 1997a). However the seasonal pattern of TBM deserves further investigation as the dynamics of root reserves is a weak point in lucerne simulation models (Confalonieri & Bechini, 2004). The objective of this experiment was to assess the seasonal variation in …
Alternative Feedbase Systems For Southern Australia Dairy Farms. 3. Economic Returns From Extra Dry Matter Consumption, D. F. Chapman, S. Kenny
Alternative Feedbase Systems For Southern Australia Dairy Farms. 3. Economic Returns From Extra Dry Matter Consumption, D. F. Chapman, S. Kenny
IGC Proceedings (1997-2023)
Growth rates of the 'traditional' perennial ryegrass pasture frequently fail to meet the seasonal feed requirements of herds in non-irrigated dairy systems in southern Australia, leading to a dependence upon additional feed at these times of the year. Farmers commonly purchase this feed off-farm, which can be costly. Growing extra feed on-farm may be more cost effective but will require additional inputs such as N fertiliser and alternative pastures/crops. The gross return to dairy farms of growing extra feed at certain times of the year can be estimated by connecting biophysical models of pasture growth to farm systems models and …
Alternative Feedbase Systems For Southern Australia Dairy Farms. 2. Seasonal Variability, S. Kenny, D. F. Chapman, D. Beca
Alternative Feedbase Systems For Southern Australia Dairy Farms. 2. Seasonal Variability, S. Kenny, D. F. Chapman, D. Beca
IGC Proceedings (1997-2023)
The standard feedbase on non-irrigated dairy farms in southern Australia is perennial ryegrass- dominant pasture supplemented by concentrate feeds, silage and hay to fill seasonal feed gaps. Using models, Chapman et al. (2005) concluded that dairy producers in this region can increase forage consumption and operating profit through the use of summer-active pastures and double-cropping (winter cereal grown for silage, followed by a summer grazing crop). However, these results were based on long-term average pasture and crop growth rates and therefore do not account for seasonal variability associated with climatic variation, which is important in southern Australia. This paper …
Alternative Feedbase Systems For Southern Australia Dairy Farms: 1. Predicted Pasture/Crop Consumption And Farm Financial Performance, D. F. Chapman, S. Kenny, D. Beca
Alternative Feedbase Systems For Southern Australia Dairy Farms: 1. Predicted Pasture/Crop Consumption And Farm Financial Performance, D. F. Chapman, S. Kenny, D. Beca
IGC Proceedings (1997-2023)
Traditional perennial ryegrass-based pastures have significant limitations for efficient feeding of dairy cattle in dryland dairy regions of southern Australia. These include strong seasonality of growth, with 50 - 60% of total annual dry matter arriving in spring and little or no growth during summer. There is clear potential for improving total forage production and the seasonality of forage supply in these regions through the use of alternative pastures (Nie et al. 2004) and fodder crops. This series of papers applies a modelling approach to investigate the potential improvements in farm productivity and profitability resulting from their use.
Modelling Of Nitrogen Allocation And Partitioning Within Lucerne (Medicago Sativa) Shoot Tissues During Recovery From Defoliation: An Approach To Estimate Forage Production And Nitrogen Composition, F. Meuriot, A. Escobar-Gutiérrez, J-C. Avice, J-C. Simon, F. Lesuffleur, F. Gastal
Modelling Of Nitrogen Allocation And Partitioning Within Lucerne (Medicago Sativa) Shoot Tissues During Recovery From Defoliation: An Approach To Estimate Forage Production And Nitrogen Composition, F. Meuriot, A. Escobar-Gutiérrez, J-C. Avice, J-C. Simon, F. Lesuffleur, F. Gastal
IGC Proceedings (1997-2023)
Lucerne has been grown over centuries for forage. Its forage production is strongly correlated to the initial taproot and stubble N reserves (Avice et al., 1996; Meuriot et al., 2004). However, the influence of cutting management on the level of N storage and the contribution of these N reserves to forage production still remain unclear and need to be studied at the whole plant level. For this purpose, a deterministic model of N allocation within the different organs and partitioning within different biochemical N pools was developed for lucerne with high and low initial N status and cutting …
Challenges In Modelling Live-Weight Change In Grazed Pastures In The Australian Subtropics, C. K. Mcdonald, A. J. Ash
Challenges In Modelling Live-Weight Change In Grazed Pastures In The Australian Subtropics, C. K. Mcdonald, A. J. Ash
IGC Proceedings (1997-2023)
In sub-tropical regions there is enormous seasonal, annual and spatial variation in pasture quality and considerable variation in quality between pasture species. The heterogeneous structure of sub-tropical pasture swards means that process based modelling of liveweight change (LWC) is particularly difficult. In response to this complexity LWC has been expressed as a function of the length of the growing season and/or pasture utilization (McKeon et al. 2000), green leaf availability, or pasture availability and climate (Hirata et al. 1993). However, these relationships vary from year to year, often fail when species composition changes, and generally explain
An Ecosystem Modelling Approach To Rehabilitating Semi-Desert Rangelands Of North Horr, Kenya, G. A. Olukoye, W. N. Wamicha, J. I. Kinyamario
An Ecosystem Modelling Approach To Rehabilitating Semi-Desert Rangelands Of North Horr, Kenya, G. A. Olukoye, W. N. Wamicha, J. I. Kinyamario
IGC Proceedings (1997-2023)
Decreased rainfall, recurrent droughts and increased anthropogenic activities have led to a dramatic increase in wind erosion on pastoral lands of North Horr resulting in the reactivation of the once-stable sand dunes. This has degraded the vegetation and impoverished the local community. Mobile sand has a severe impact on dry season grazing areas (Omar & Abdal, 1994) and, therefore, affects pastoral livestock production. In North Horr, Suaeda monoica is important in camel production and for stabilising sand dunes but it has been over-utilized over the years. The objective of this study was to use ecosystem modelling approaches to examine the …
Modelling Winter Grass Growth And Senescence, D. Hennessy, S. Laidlaw, M. O'Donovan, P. French
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 …
Visual Modelling Of Alfalfa Growth And Persistence Under Grazing, S. R. Smith Jr., L. Muendermann, A. Singh
Visual Modelling Of Alfalfa Growth And Persistence Under Grazing, S. R. Smith Jr., L. Muendermann, A. Singh
IGC Proceedings (1997-2023)
A ‘virtual’ alfalfa plant model was developed at the University of Manitoba in Canada as part of a comprehensive grazing research project. This model shows an alfalfa plant ‘growing’ on a computer screen and the plant’s response to grazing (similar to time-lapse photography). The original model was constructed by Singh (2005) to show the research potential of visually modelling alfalfa plant growth. The ability to visually ‘grow’ a plant on a computer screen also offers tremendous opportunities for teaching and extension. Detailed morphological measurements were used in the construction of Singh’s model, based on single plants subjected to the following …
Autumn Root Reserves Of Lucerne Affected Shoot Yields During The Following Spring, D. J. Moot, E. I. Teixeira
Autumn Root Reserves Of Lucerne Affected Shoot Yields During The Following Spring, D. J. Moot, E. I. Teixeira
IGC Proceedings (1997-2023)
Frequent grazing affects shoot yield of lucerne (Medicago sativa L.) by limiting radiation interception (Teixeira et al., 2005b) and the accumulation of endogenous reserves (C and N) in perennial storage organs like crowns and taproots (Teixeira et al., 2005a). In temperate regions, the impact of low level of perennial reserves is particularly evident during early-spring, when lucerne regrowth resumes after an overwintering period. The analysis of lucerne yield can be fragmented into its yield components of plant population, shoots per plant and yield per shoot (Volenec et al., 1987). The objective of this research was to quantify …
Lucerne Crown And Taproot Biomass Affected Early-Spring Canopy Expansion, E. I. Teixeira, D. J. Moot, A. L. Fletcher
Lucerne Crown And Taproot Biomass Affected Early-Spring Canopy Expansion, E. I. Teixeira, D. J. Moot, A. L. Fletcher
IGC Proceedings (1997-2023)
Leaf area index (LAI) quantifies canopy expansion in crops and is used in lucerne (Medicago sativa L.) simulation models to predict daily PAR interception (PAR i). This then drives yield through radiation use efficiency (RUE) (Gosse et al., 1984). In perennial crops, like lucerne, the level of biomass stored in crown and taproot may affect canopy expansion in subsequent regrowth cycles (Avice et al., 1997). In temperate regions the impact of this is likely to be greatest in early-spring, when low temperatures delay development. The objective of the current research was to identify whether contrasting levels of winter biomass in …
A Bidirectional Deep Lstm Machine Learning Method For Flight Delay Modelling And Analysis, Desmond B. Bisandu, Irene Moulitsas
A Bidirectional Deep Lstm Machine Learning Method For Flight Delay Modelling And Analysis, Desmond B. Bisandu, Irene Moulitsas
National Training Aircraft Symposium (NTAS)
Flight delays can be prevented by providing a reference point from an accurate prediction model because predicting flight delays is a problem with a specific space. Only a few algorithms consider predicted classes' mutual correlation during flight delay classification or prediction modelling tasks. None of these existing methods works for all scenarios. Therefore, the need to investigate the performance of more models in solving the problem of flight delay is vast and rapidly increasing. This paper presents the development and evaluation of LSTM and BiLSTM models by comparing them for a flight delay prediction. The LSTM does the feature extraction …