APSRU PROJECT SUMMARY NO. 7

Project Title:                        Modelling crop growth and yield under the environmental changes induced by windbreaks

Project Supervisor:            Dr PS Carberry, Dr H Meinke

Funding Body:                     RIRDC

Admin Contact:                Marshall Mackay, CSIRO

Commencement Date:        1/7/93                                     Completion Date: 30/6/98

Aims:

In order to answer the question "Why do windbreaks work?", this project addresses the hypothesis #1 (as identified the RIRDC windbreak workshop) that windbreaks influence the crop water and energy balances, thence affecting crop temperature and plant growth. To achieve this goal, the project objectives are:

(i) To translate the impact of measurable differences in microclimate induced by windbreaks into physiological changes in crop growth, development and yield through the application of validated crop simulation models to data from windbreak experiments conducted at selected locations throughout Australia.

(ii) To quantify the potential benefits and the likelihood of windbreak effects on crop production through an economic analysis of crop yields predicted for the historical climate records at selected sites and for the expected range in microclimatic change induced by windbreaks.

Research Proposal Summary:

Recent reports in Australia have attributed enhanced crop yields to the presence of tree windbreaks on farms. In order to answer how this can happen, this project addresses the hypothesis that windbreaks influence the crop water and energy balances. The project's contribution to the National Windbreak Program is to provide crop modelling input into the interpretation of the field experimentation of sister projects and to combine with the micrometeorological modelling efforts to extend research results beyond the specific years and sites studied, to the wider farming community. Thus, to achieve this, the project objectives are:(i) to translate the impact of measurable differences in microclimate induced by windbreaks into physiological changes in crop growth, development and yield through the application of validated crop simulation models to data from windbreak experiments conducted at selected locations throughout Australia; and(ii) to quantify the potential benefits and the likelihood of windbreak effects on crop production through an economic analysis of crop yields predicted for the historical climate record at selected sites in Australia and for the expected range in microclimatic change induced by windbreaks.         

The project will use APSRU's models of wheat and maize which simulate crop development, growth and yield in response to soil water and nitrogen balances. Climatic inputs are daily solar radiation, maximum and minimum air temperatures, rainfall, vapour pressure deficit and (optionally) windspeed. To simulate results obtained from the collaborating field studies, relevant data will be collected at all sites both to parameterize the models (soil parameters, initial soil conditions and agronomic information) and to test their predictions (crop growth data, soil water balance) for points on a transect from adjacent to the windbreaks to 'open-grown' areas. Climate data inputs to the crop models will be those simulated using the model of windbreak micrometeorology (developed in a sister project) using standard weather data collected at each experimental site. The basis of analysis will be the comparison of measured and predicted crop responses to the altered microclimate induced by windbreaks. Of primary interest is the degree to which the measured crop response can be attributed to changes in the temperature and humidity microclimate. At the completion of the experimental phase, models for wheat and maize crops will have been calibrated and tested at a range of sites and seasons. Using windbreak-modified climatic data and these models, crop yields can be predicted for the historical climate data as altered by a select variety of windbreaks at representative sites throughout Australia. The economics of crop production with/without windbreaks will then be quantified. The benefits from this project, in association with the others within the National Windbreak Program, will be in providing estimates of the economic benefits that grain producers in Australia can expect from tree windbreaks. With the environmental movements within Australia arguing for increasing trees on farms, confirmation and quantification of enhanced crop yields due to tree windbreaks will enhance the incentive for farmers to plant trees.

Potential Outcomes:

There is increasing public pressure for more trees on farmlands. The cost of achieving this, however, falls largely on the farming community. Convincing evidence to support an economic benefit to crop productivity from the planting of trees in windbreaks would greatly enhance the incentive for increasing the farm land under trees. This project, in conjunction with the others within the National Windbreak Program, will provide estimates of the economic benefits that wheat producers in southern Australia and maize growers on the Atherton Tablelands can expect from windbreaks.

This project has been developed under the co-ordination of RIRDC's National Windbreak Program.

Project Publications: