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Rural Industries
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|| Introduction || Project listing|| Project Summaries ||
Climate change and the so called 'greenhouse effect' pose both threats and opportunities for Australian agriculture. Higher carbon dioxide levels will enhance plant growth rates, lower rainfall, and reduce soil moisture availability.
Reduced productivity overseas will offer market opportunities, but a climatic shift in Australia may reduce our production base. RIRDC has a small strategic program of research on climate change specifically orientated to the likely impact on agricultural industries.
The Corporation provides a coordinating role for rural industry research funding interest in climatic change and greenhouse effect issues.
Research Highlights for 1996-97
· Determination of the potential for carbon sequestration in Australian agricultural soils.
· Workshop on the impact on the impact of global change on Arthropod pests, weeds and diseases.
· Assessment of the potential productivity benefits to tropical and subtropical tree fruit and nut crops from elevated CO2 levels.
· The Climate Variability program, jointly funded with LWRRDC and other agencies, convened a national conference on the Development of a National Drought Alert Program which indicated that current long term RIRDC projects would be highly valuable to that strategy.
POTENTIAL PRODUCTIVITY BENEFITS TO TROPICAL AND SUBTROPICAL TREE FRUIT AND NUT CROPS FROM ELEVATED CO2 LEVELS
Objective
· To investigate the effect of atmospheric CO2 enrichment through the production of 'greenhouse gases' on potential opportunities for improved yield and quality of subtropical and tropical tree fruit and nut crops (avocado, macadamia and mango) in northern Australia.
Background
'Greenhouse gas' emissions are predicted to increase mean temperatures (1-2°C in the tropics) and atmospheric CO2 concentrations. There is ample evidence that CO2 enrichment of the atmosphere leads to a substantial increase in plant biomass production in C3 species. However, this will only be beneficial if dry matter partitioning favours increases in the harvest index. This study investigates potential productivity benefits for subtropical and tropical tree fruit and nut crops from predicted increases in atmospheric CO2 concentrations.
Research
The research consisted of 3 integrated areas: defining CO2 response curves and the effects of sink limitation on CO2 assimilation for the three crop species investigated; studying nutrient and photoassimilation dynamics during long-term exposure to CO2 enriched atmospheres; and determining the impact of CO2 enriched atmospheres on fruit and nut retention, growth and yield.
Outcomes
The three C3 crop species studied in this project was highly responsive to CO2 enrichment with short-term assimilation rates increasing by 50 to 80 percent at the 2050 projected atmospheric CO2 concentrations of 450-520 µmol CO2 mol-1. While this represents a significant increase in photosynthetic capacity of these fruit and nut crops the benefits of CO2 enrichment were diffused when root systems (sinks) were constricted (container-grown trees).
Following long-term exposure to CO2 enriched atmospheres there was a reduction in CO2-use efficiency by the three crop species. However, the rate of CO2 assimilation remained significantly higher (» 40%) than those trees grown at the ambient atmospheric CO2 level (350 µmol mol-1). In a study with mangoes, leaf levels of some nutrients declined following long-term exposure to enriched CO2 atmospheres. In particular P and the trace elements Fe, Cu and B showed a significant reduction in leaf concentration and trees developed chronic boron deficiency.
Trees grown in CO2 enriched atmospheres retained higher numbers of fruitlets during the post-flowering period indicating that fruiting is source-limited. Increased retention translated into a significant increase in fruit yield with mean fruit/nut size enhanced.
Implications
The increased demand for nutrients under enriched CO2 atmospheres, particularly boron, has implications for tree fruit and nut crops growing in northern Australia. Most soils used for horticultural production in this region occur in high rainfall (< 1000 mm pa) areas which have been subjected to leaching. Boron is deficient in these areas and appropriate application is necessary throughout the year to control the problem. With some crops (e.g. avocados) uptake is already difficult to achieve and increased requirements due to future elevated CO2 concentrations will place an additional burden on the production of these crops. This may be partially offset by the selection and development of superior rootstocks as boron uptake has been shown to be genetically influenced.
There is a clear indication that elevated atmospheric concentrations of CO2 will improve the productivity of fruit tree crops through increased fruit retention. There is also the potential to improve fruit quality through increased kernel size in macadamia and larger fruit size in avocado cultivars where this is a problem in warm climates.
RIRDC Project No: DAQ-156A
RESEARCHER: Mr Tony Whiley
ORGANISATION: Qld Dept. of Primary Industries,
GPO Box 46 BRISBANE QLD 4001
PHONE: 07 3441 2211 FAX: 07 3441 2235
POTENTIAL FOR CARBON SEQUESTRATION IN AUSTRALIAN AGRICULTURAL SOILS
Objectives
· To estimate the size and turnover rates of carbon pools in a range of Australian agricultural soils under varying environments.
· To determine the charcoal content in the inert fractions of these soils.
· To optimise the Rothamsted and SOCRATES carbon models for Australian conditions.
· To determine which management practices have the potential to sustain or increase soil organic matter in the long and short term in Australian agricultural soils.
Background
Soil carbon is significant in the global carbon budget, equating to a reservoir of twice the atmospheric pool and about one half of all the known fossil fuel reserves. Carbon simulation models, which are used to predict the distribution of carbon in a number of conceptual pools, can be used to predict changes in soil organic carbon provided that these pools can be measured. Of these pools, inert carbon (IOM), identified by 13 C-NMR to occur mostly as charcoal, has a major effect on the long-term prediction of carbon.
The Division of Soils has recently developed a photo-oxidation technique to determine this fraction. After optimisation for Australian conditions, the calibrated computer models can be used to predict the carbon dynamics of major soil types under the common cereal/pasture rotations used in Australia. This information enables modelling to be performed with greater confidence to predict the sequestration of soil organic carbon resulting from different agricultural rotations and global climate changes.
Research
The research was in two areas: the identification and quantification of the carbon in the lablle, humic and IOM carbon pools in selected soils from long-term and short-term field trials by fractionation techniques and 13 C-NMR spectroscopy; and in the long-term prediction of soil carbon levels using carbon models.
Outcomes
Soil residues left after uv-photo-oxidation and HF acid treatment were characterised as having a plant cellular morphology and a strong 160-110ppm 13 C-NMR signal. This material (averaging 26% of all soil organic carbon for the samples analysed) was the source of carbon inert to biological degradation through physical or chemical protection. The major component of this inert pool in most soils was identified as charcoal.
The data from laboratory soil fractionation's and uv-photo-oxidation was used to determine an optimum set of parameters for two carbon dynamics models: Rothamsted and SOCRATES. Computer simulations fitted the known carbon data reasonably well, taking into account the usual soil and cropping variability. As expected, the rate of carbon sequestration resulting from high yielding continuous pastures was sufficient to maintain or increase carbon levels but all other crop/pasture rotation resulted in a decline of surface soil carbon. Soils high in IOM were less susceptible to carbon loss than those with low IOM levels.
Simulations extended to 100 years from present showed that for most sites under conventional cropping, carbon sharply declined after initial clearing of native vegetation with further gradual decline to low levels. Approximately one half to a third of carbon remaining after 100 years cultivation was inert.
Implications
Land subjected to historic burning of native grasses can have build up high concentrations of charcoal. Alluviation can concentrate charcoal, along with other clay-sized materials in some soil types such as black earths. As a major component of the inert pool, charcoal which is determined as organic carbon by all conventional soil organic carbon methods of analysis, can be misleading in terms of carbon status, particularly if carbon is implicated with soil structure and nutrients. This non-inert fraction has been shown to decline with conventional cropping practices and the long-term prognosis for further losses is not good. This decline in carbon can be largely reversed by the use of high yielding pastures either in rotations or as a monoculture.
RIRDC Project No: CSO-5A
RESEARCHERS: J. O. Skjemstad, L. J. Janik
ORGANISATION: CSIRO Division of Soils Waite Road, URRBRAE SA 5064
PHONE: 08 303 8445 FAX: 08 303 8427
IMPACT OF GLOBAL CHANGE ON ARTHROPOD PESTS, WEEDS AND DISEASES - WORKSHOP
Objectives
· To produce an assessment of the likely impacts of global
change on arthropod pests, weeds and diseases, and facilitate and conduct
· To facilitate and conduct a workshop on the Impact of Global Change
on Arthropod Pest, Weeds and Diseases of Australia Terrestrial Ecosystems.
Research
The research consisted of a review of the impacts of global climate change on pests, diseases and weeds in Australia in the light of the latest overseas findings. In addition a case study was prepared to act as a basis for international evaluation of Australia's capability to conduct national impact assessments. The results of the study were presented on the www homepage: http://www.modeling.ctpm.uq.edu.au/dest_public/, also accessible through the CSIRO Entomology and IGBP-GCTE Homepages.
Outcomes
The workshop was held in Brisbane from 9-12 October 1996 and the report on state of the art assessment of the likely impacts of pests, weeds and diseases in Australia was published in December 1995. Feedback was received to the effect that the workshop was the most useful and well run that many national and international scientists had ever attended. An implementation plan for a collaborative international research program was prepared for IGBP-GCTE and published in June 1996.
Implications
Global climate change is now generally accepted as being a reality and emphasis has now moved to evaluate potential impacts on different sectors of society. Agriculture is likely to affect more than most industry sectors and it is important for it to anticipate new climatic conditions that can no longer be predicted from past experience. A national capability to evaluate impacts is a priority and pests, diseases and weeds need early attention, given their potential to cause major adverse impacts.
The research has provided a 'no regrets' introduction to research approaches that are suitable to assist industry exploit newly emerging opportunities arising from the growing ability to provide climate forecasts up to 12 months in advance. There are a number of opportunities arising for international collaboration on global change research through IGBP-GCTE if the Australian effort can be maintained.
RIRDC Project No: GCT-1A
RESEARCHER: R W Sutherst
ORGANISATION: CSIRO Entomology,
GPO Box 1700, CANBERRA ACT 2601
PHONE: 02 6246 4008 FAX: 02 6246 4095
Last updated: 25 October1997
Copyright © RIRDC
http://www.rirdc.gov.au/pub/97comp/climate.html