Lisa E. Brennan

A framework for simulating agroforestry options for the low rainfall areas of Australia using APSIM

The long-term benefits of retaining or planting trees on farms to rehabilitate land and protect the soil from erosion or salinity problems has to be traded off against the impact of tree competition on commercial crops, especially in the medium to low rainfall regions of Australia. The incentive to plant trees would increase if tree competition could be offset by economic returns gained from farm forestry products and by the beneficial impacts of tree windbreaks on crop yields and resource sustainability. The Agricultural Production Systems Simulator (APSIM) has a well-established capability to simulate cropping systems and this paper reports on progress in applying APSIM to agroforestry systems in order to quantify the potential benefits and risks of planting trees as windbreaks to cropping land in Australia. A simple case study indicating one possible model configuration is used to demonstrate this emergent capability for simulating tree and crop productivity and their interactions. The simulated agroforestry system consisted of the growth of a belt of trees (Eucalyptus argophloia) positioned as a windbreak on the edge of a field where a crop of winter chickpea (Cicer arietinum L.) is grown over a 30-year period. The example simulations quantify the yield and economic returns of annual chickpea crops in addition to the discounted economic return from timber production after 30 years of tree growth. This example demonstrates how APSIM can be used to quantify the economic tradeoffs in planting trees as windbreaks on a commercial farm in a low rainfall region of Australia.

An evaluation of the tactical use of lucerne phase farming to reduce deep drainage

Lucerne phase farming has been suggested as a way of reducing deep drainage in the cereal belt of southern Australia. It is based on the concept that lucerne (Medicago sativa L.), a perennial pasture with a deep root system, creates a soil water storage buffer below the root zone of the annual crops, which gradually refills during the subsequent cropping phase, temporarily reducing the risk of deep drainage. The rate of refilling is variable because it is affected by the amount and distribution of rainfall as well as management of the crop and the summer fallow. There is, therefore, uncertainty about the optimum phase durations that will maximise the effect of the lucerne phase. Computer simulations were applied to evaluate the use of a soil water measurement below the root zone of annual crops to schedule the phase changes, referred to as tactical phase farming. The results confirmed that phase farming reduced average annual deep drainage significantly, but at the cost of lower average annual gross margin. In most cases, tactical phase farming improved the trade-off between deep drainage and gross margin relative to fixed duration phases; for a given amount of average annual deep drainage the average annual gross margin was larger, and for a given gross margin the drainage was smaller. The benefits of tactical phase systems were greatest in soils with a large available water-holding capacity and when the variability of the refilling rate was large. Overall, however, the benefits of the tactical approach relative to fixed phase systems were small.

Economic benefits of variable rate technology: case studies from Australian grain farms.

In this study we attempt to quantify the economic benefits of the adoption of variable rate application of fertiliser on six case study farms from the Australian wheatbelt. The farm case studies covered a range of agro-climatic regions (Mediterranean, uniform, and summer-dominant rainfall patterns), cropping systems (wheat–lupin, wheat–canola, and winter and summer crops), farm sizes (1250–5800 ha cropping program), soil types (shallow gravels to deep cracking clays), and production levels (average wheat yields from 1.8 to 3.5 t/ha). The farmers had been practising some form of variable rate technology (VRT) management of fertiliser for 2–10 years. Capital investment in VRT equipment ranged from

A farm-scale, bio-economic model for assessing investments in recycled water for irrigation

37 000 to

Pay-offs to zone management in a variable climate: an example of nitrogen fertiliser on wheat

73 000, which is at the medium to high end of investment for Australian farmers, and when expressed as investment per cropped hectare it varied from

An evolutionary economic perspective on technical change and adjustment in cane harvesting systems in the Australian sugar industry

11 to

A participatory, farming systems approach to improving Bali cattle production in the smallholder crop–livestock systems of Eastern Indonesia

30/ha. All farmers were able to quantify benefits of VRT, ranging from

Learning from the historical failure of farm management models to aid management practice. Part 1. The rise and demise of theoretical models of farm economics

1 to

Can Renewable Energy Contribute to a Diversified Future for the Australian Sugar Industry

22/ha across the six farms, and a break-even analysis showed that the initial capital outlay was recovered within 2–5 years. On a per paddock basis, benefits ranged from –

Back to the future - Reinventing farm management economics in farming systems research

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