Wind erosion and rising water tables are serious threats to the ecological sustainability of annual plant-based farming systems on deep, infertile sandplain soils in southwestern Australia, In this study, an annual cropping system was compared with two novel perennial plant-based systems designed to address these threats in terms of their use of renewable indigenous resource, their use of non-renewable indigenous resources, their purchased inputs of energy and materials, and profitability. The farming systems were an annual lupin/wheat (Lupinus angustifolius L.lTriticum aestivum L.) crop rotation, a plantation of the fodder tree tagasaste (Chamaecytisus proliferus L.) and an alley cropping system in which the lupin/wheat rotation was grown between spaced rows of tagasaste trees. Flows of energy and materials between the environment and the economy were identified for each farming system and the natural and human activity involved in generating inputs as goods or services then valued in terms of the equivalent amount of solar energy required for their production using the emergy method of Odum [Ecological and General Systems: An Introduction to Systems Ecology. University Press of Colorado, revised edition of Systems Ecology, 1983, Wiley, New York, 644 pp.; Environmental Accounting: Emergy and Environmental Decision Making. Wiley, New York, 370 pp.]. The results showed that the two largest energy flows in the conventional lupin/wheat cropping system were wind erosion and purchased inputs of phosphate. The renewable component of production was 15% of total flows in the lupin/wheat system, 30% in the alley cropping system and 53% in the tagasaste plantation. The annual net income from the plantation system was nearly four times higher, and from alley cropping 45% higher, than from the lupin/wheat rotation. This analysis suggested that once the two agroforestry systems were fully established, the tagasaste plantation was the most efficient at transforming natural resources into goods and services and the most profitable, while the lupin/wheat system was the least energy efficient and the least profitable.

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The effect of weed harrowing direction and driving speed (5, 9 and 13 km/hour) was studied in field experiments in Sweden for three years. Weed harrowing was performed when the test crop (Avena sativa) had developed 3-4 leaves. Effects were studied on both weeds and crop. Special attention was given to the degree of soil cover on the oat plants as a measurement of the intensity of the weed harrowing. Harrowing across the plant rows gave a higher degree of soil covering than weed harrowing along the rows. Increased driving speed caused more soil to cover the oat plants. Grain yield was significantly affected at higher driving speed in two of the three years. Driving direction did not significantly influence grain yield. The reduction of both the number and weight of the weeds was found to be dependent on driving speed, and most of the weed reduction was obtained at 5 km/hour. Harrowing direction did not significantly affect the weeds. The degree to which the crop was covered with soil does not seem to be a good quantitative parameter for measuring the intensity of the weed-harrowing when comparing different driving directions.

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