Frost damage remains a major problem for broadacre cropping, viticulture, horticulture and other agricultural industries in Australia. Annual losses from frost events in Australian broadacre agriculture are estimated at between $120 million and $700 million each year for this sector. Understanding the changing nature of frost risk, and the drivers responsible, are important steps in helping many producers manage climate variability and change. Our analysis, using Stevenson screen temperature thresholds of 2°C or below as an indicator of frost at ground level, demonstrates that across southern Australia, despite a warming trend of 0.17°C per decade since 1960, ‘frost season’ length has increased, on average, by 26 days across the whole southern portion of Australia compared with the 1960–1990 long-term mean. Some areas of south-eastern Australia now experience their last frost an average 4 weeks later than during the 1960s. The intersection of frost and wheat production risk was quantified at 60 sites across the Australian wheatbelt, with a more in-depth analysis undertaken for 15 locations across Victoria (i.e. eight sites common to both the National and Victorian assessments and seven sites exclusive to the Victorian analysis). The results of the national assessment highlight how frost-related production risk has increased by as much as 30% across much of the Australian wheatbelt, for a range of wheat maturity types, over the last two decades, in response to an increase in later frost events. Across 15 Victorian sites, sowing dates to achieve anthesis during a period with only a 10% chance of a 0°C night occurring shifted by 23 days (6 June) for the short-season variety, 20 days (17 May) for the medium-season variety and 36 days later (9 May) for the long-season variety assessed.

Grain yields vary widely between seasons in rain-fed agriculture. The yield variability is strongly influenced by rainfall variability and a number of related crop management decisions. This is well recognised in the literature through the use of seasonal rainfall forecasts applied to the main cropping decisions. However, the value of short-term 10-day rainfall forecasts for management decisions in cropping has not yet been quantified. Here we report on the potential benefits of a hypothetical, always-correct 10-day rainfall (greater than 10 mm in three days) forecast used to determine early and late in-season crop management decisions.Most of the analysed applications of short-term rainfall forecasts show a significant increase in cropping profitability depending on rainfall region and soil type. Using a 10-day rainfall forecast to dry-sow prior to the traditional start of sowing at the first autumn rainfall can yield an extra A$20,000 to A$200,000 for a typical farm (i.e. A$10 to A$100/ha for a 2000 ha cropping programme). The same forecast type can be used to determine late in-season decisions on N fertiliser, and fungicide applications to control rust at the end-of-ear growth stage. In the one-third of seasons with late rainfall, the increased yield or decreased fungal damage can lead to benefits of A$10 to A$160/ha. When 10-day rainfall forecasts are applied together within a season, the extra benefits from correct short-term forecasts can be cumulative.Fine-tuning the forecast length, rainfall thresholds and exploring other possible crop decisions could lead to further increased returns in cropping from short-term rainfall forecasts. Ultimately, using hind-casts of short-term rainfall forecasts to measure the forecast skill and the implication of occasional non-correct forecasts will determine the actual value of such forecasts. (C) 2015 Elsevier B.V. All rights reserved.

Decision support systems (DSS) that provide advice on best N fertiliser management practice ideally need to assess the effect that fertiliser type, rate and management have on N loss. Currently only nitrate leaching and denitrification losses can be assessed in Australian DSS that use output from the Agriculture Production Simulator (APSIM). This paper describes a simple spreadsheet-based model for estimating NH3 loss from urea, urea ammonium nitrate and ammonium sulfate that can be used in conjunction or independent of current DSS. The use of scaling factors that reduce NH3 emission on the basis of factors known to be key determinants of NH3 loss, including type of fertiliser used, rate of fertiliser applied, management of fertiliser, rainfall and crop development was found to account for 85% of the variance between predicted and observed values when tested against 40 case studies. The model also had good predictive power with a root mean square error (RMSE) equivalent to 4.8% of N applied.

We produced an interactive farm game for use in workshops conducted with farmers, grower group staff, advisers and researchers. The workshops aimed to explore possible consequences of combinations of future management, land-use options and climatic factors in a no-risk, virtual manner. The game workshop was conducted with 52 participants at five locations across the wheatbelt of Western Australia. Seventy-four per cent of participants considered that the workshop helped them to consider options that would be useful on their farms. While acknowledging the simplifications inherent in a game, participants considered that much of the 'game-play' reflected their real decision-making. The opportunity to hear the decision-making of others, and to observe the effects, was of particular value. These findings illustrate the potential for the game-workshop approach to explore complexity in dimension, time and space and, particularly, to identify information needs for farmers in a specific region. They also highlight the decisions that would be made on farm in the absence of constraints of time, capital and logistics. (Resume d'auteur)

Achievable grain yields can vary widely between seasons in rain-fed agriculture. Adjusting N fertiliser inputs according to achievable grain yields could reduce over-fertilisation in low-yielding seasons and allow increasing gross margins in potential high-yielding seasons. Seasonal rainfall forecasts from the coupled ocean-atmosphere global circulation model POAMA were skill tested and employed for N fertiliser decision making in the Western Australian wheat-belt. The POAMA seasonal rainfall forecast showed significant skill in forecasting rainfall season types in southern regions of the Western Australian wheat-belt. This skill resulted in about A$50 ha(-1) of additional benefits when used in N management decisions in wheat cropping. However, such a forecast should not be used without considering other systems knowledge available to farmers. Combining a forecast with systems information such as initial soil water conditions can be crucial in obtaining value from a forecast. Another important factor to consider is the risk behaviour of farmers, where the gross margin from additional fertiliser is expected to exceed the cost by a factor of two or more. Finally, variations in fertiliser cost and wheat prices are critical in determining the benefits from using a forecast system for management decisions in agriculture. Using a forecast for only the wet season-type can further increase a forecast value because the additional gains in wet seasons are often higher than the savings from reduced fertiliser in dry seasons. It is expected that skilful seasonal forecasting systems will become increasingly valuable in regions where rainfall is decreasing because they help to capture benefits in the declining number of potentially high-yielding seasons and minimise the losses in the increasing number of low-yielding seasons. Published by Elsevier B.V.

Seasonal rainfall forecasts have been shown to have significant skill in many parts of the world. In this study, seasonal forecasts were used together with a crop simulation model and a simple pasture growth curve to inform several decisions on year-to-year farm management, including on land-allocations in a mixed wheat-sheep farming system. In seasons where "above-median" rainfall was forecast, N fertiliser applications in cropping were increased to support the higher grain yield potential, sheep stocking rates were increased to take advantage of higher pasture growth and unused pasture land was made available for cropping. In seasons where "below-median" rainfall was forecast. N fertiliser applications in cropping were reduced to minimise costs, and traditional conservative sheep stocking rates were used. Application of the Predictive Ocean Atmosphere Model for Australia (POAMA) seasonal rainfall forecast yielded additional profit of up to A$66 ha(-1) per annum, equivalent to A$200,000 y(-1) for an average size farm in Western Australia. The largest benefit from applying a forecast in wheat-sheep farms comes from the increase of more profitable cropping during "above-median" rainfall seasons. This is well above the benefit of previous single-commodity forecast applications, and therefore has widespread potential to improve decision making on mixed crop-livestock farms. With the projected decline of rainfall in the Australian and other rain-fed crop-livestock regions of the world, skilful seasonal forecasting systems will become increasingly valuable as they will assist farm managers to capture the benefits in the declining number of potentially high-production seasons and minimise the input costs in the increasing number of low-production seasons. (c) 2012 Elsevier Ltd. All rights reserved.

Under a future climate for south-eastern Australia there is the likelihood that the net effect of elevated CO2, (eCO2) lower growing-season rainfall and high temperature will increase haying-off thus limit production of rain-fed wheat crops. We used a modelling approach to assess the impact of an expected future climate on wheat growth across four cropping regions in Victoria. A wheat model, APSIM-Nwheat, was performance tested against three datasets: (i) a field experiment at Wagga Wagga, NSW; (ii) the Australian Grains Free Air Carbon dioxide Enrichment (AGFACE) experiment at Horsham, Victoria; and (iii) a broad-acre wheat crop survey in western Victoria. For down-scaled climate predictions for 2050, average rainfall during October, which coincides with crop flowering, decreased by 32, 29, 26, and 18% for the semiarid regions of the northern Mallee, the southern Mallee, Wimmera, and higher rainfall zone, (HRZ) in the Western District, respectively. Mean annual minimum and maximum temperature over the four regions increased by 1.9 and 2.2°C, respectively. A pair-wise comparison of the yield/anthesis biomass ratio across climate scenarios, used for assessing haying-off response, revealed that there was a 39, 49 and 47% increase in frequency of haying-off for the northern Mallee, southern Mallee and Wimmera, respectively, when crops were sown near the historically optimal time (1 June). This translated to a reduction in yield from 1.6 to 1.4 t/ha (northern Mallee), 2.5 to 2.2 t/ha (southern Mallee) and 3.7 to 3.6 t/ha (Wimmera) under a future climate. Sowing earlier (1 May) reduced the impact of a future climate on haying-off where decreases in yield/anthesis biomass ratio were 24, 28 and 23% for the respective regions. Heavy textured soils exacerbated the impact of a future climate on haying-off within the Wimmera. Within the HRZ of the Western District crops were not water limited during grain filling, so no evidence of haying-off existed where average crop yields increased by 5% under a future climate (6.4–6.7 t/ha). The simulated effect of eCO2 alone (FACE conditions) increased average yields from 18 to 38% for the semiarid regions but not in the HRZ and there was no evidence of haying-off. For a future climate, sowing earlier limited the impact of hotter, drier conditions by reducing pre-anthesis plant growth, grain set and resource depletion and shifted the grain-filling phase earlier, which reduced the impact of future drier conditions in spring. Overall, earlier sowing in a Mediterranean-type environment appears to be an important management strategy for maintaining wheat production in semiarid cropping regions into the future, although this has to be balanced with other agronomic considerations such as frost risk and weed control.