School of Agriculture, Food and Ecosystem Sciences - Theses

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End date: 1989 × Start date: 1986 × Type: Masters Research thesis × Subject: Agroforestry ×

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    Agroforestry : a study of agroforestry extension and a model of light interception in agroforestrry
    Reid, Rowan ( 1986)
    This thesis examines two important aspects of agroforestry in Australia: agroforestry as an agricultural innovation and light interception by the tree crop. (1) Agroforestry as an innovation The ideas and opinions of farmers and professionals involved in agroforestry in Australia were studied by mail-return questionnaires. Questionnaires were sent to all farmers and professionals known to be actively involved in agroforestry. - The study is not a statistical survey of a population. The potential of agroforestry as an agricultural innovation is discussed with reference to the response to the survey and the literature. The need for a universally accepted classification of agroforestry practices is demonstrated and a system suitable for agroforestry in Australia and New Zealand developed. The classification is an adaption of agroforestry classifications developed for use in less industrially developed countries. The adopters of agroforestry involved in the study are shown to be more educated, of-higher social status, and more innovative than farmers in general. Most show opinion leader status within their local community and have a positive attitude towards agroforestry, as do the professionals involved in the research and extension of agroforestry. It is argued that agroforestry adoption is following the general trend of innovation adoption and can be expected to be adopted at an increasing rate in the near future. Factors that may limit the extent or rate of adoption are identified and a strategy developed to ensure good two-way communication between researchers and potential adopters so as to encourage successful adoption of agroforestry by interested farmers. (2) Light interception Light is shown to be a major limiting factor affecting agricultural production in agroforestry. Light interception by the tree crop reduces light availability at ground level and therefore growth of agricultural crops. Past models of light interception by discontinuous tree canopies are reviewed and a new computer based model developed. The model, TREE-SHADE, allows estimates to be made of the light interception by a stand of widely spaced trees at any time on any date. Input variables include the nature of the site, the mean size and shape of the tree crop, the spatial arrangement of the trees and the times and dates of interest. The model is tested against field results collected in a seven year old agroforest of Pinus radiata near Canberra. The model was shown to slightly underestimate solar radiation availability at ground level beneath the trees. The difference was partly explained by variability in spacing and was not considered significant enough to detract from the value of the model.