Abstract Farm gross margins for canola are directly tied to yield, yet growers miss out on ∼40−50% of water-limited potential yields (YW). Many factors including weather variability can limit returns on production expenditure and lead growers to moderate inputs that also limit yield. The purpose of this study was to identify management practices that growers could use most profitably under differing seasonal conditions. Canola crop yields were simulated with APSIM at seven diverse Australian locations in a factorial array of management practices including sowing date, sowing density, cultivar, rate of cultivar development and nitrogen fertiliser rate. The implication for growers of input costs for the different management combinations was evaluated in terms of the extent that costs were recovered (ratio of gross margins to variable costs) and magnitude of variable input costs for gross margins. A regression-tree data-mining approach was used to identify the most profitable and highest yielding combinations of management practices. Environmental conditions (defined here by combinations of date of sowing and ‘perfect knowledge’ of growing season rainfall) had greatest impact on gross margins and few profitable management practices could be identified unless environmental conditions were first accounted for. When crop management practices were tailored to rainfall and sowing date to maximize gross margins, yields were up to 2 Mg ha−1 greater than the average yield achieved by industry. Yield generally increased in response to increasing variable costs but gross margins tended to plateau; after this point higher variable input costs were matched but not exceeded by revenue from increased yield. Gross margins changed in response to individual management factors: for sowing date, gross margins decreased with progressively later sowings from mid-March. For N fertiliser rate in all sowing dates, it was more profitable to use higher N fertiliser rates for higher rainfall deciles, and to use lower N rates as sowing was delayed. Cultivars with slow to medium rates of development were most profitable for early sowings up to the end of April, except where rainfall was low (in low rainfall deciles or for locations in low rainfall zones). Hybrid and conventional open-pollinated cultivars had similar gross margins, which were greater than for the Triazine-tolerant open pollinated cultivar due to its lower yield potential. Selection of most profitable practices was enhanced with knowledge of seasonal rainfall, but time of sowing matched with rate of development and a non-TT-OP cultivar could be selected to maximise gross margins without knowledge of rainfall. Nevertheless, high costs of production may hinder the most profitable selection of management practices.

中文翻译：

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最大限度提高澳大利亚油菜 (Brassica napus L.) 毛利率的管理实践

摘要油菜籽的农场毛利率与产量直接相关，但种植者错失了约 40-50% 的限水潜在产量 (YW)。包括天气变化在内的许多因素会限制生产支出的回报，并导致种植者减少也会限制产量的投入。本研究的目的是确定种植者在不同季节条件下可以最有利可图的管理方法。在澳大利亚七个不同地点使用 APSIM 模拟了一系列因子管理实践中的油菜作物产量，包括播种日期、播种密度、栽培品种、栽培品种发展速度和氮肥施用量。不同管理组合的投入成本对种植者的影响是根据成本回收的程度（毛利率与可变成本的比率）和毛利率的可变投入成本的大小来评估的。回归树数据挖掘方法用于确定最有利可图和收益最高的管理实践组合。环境条件（这里由播种日期和生长季节降雨量的“完美知识”的组合定义）对毛利率的影响最大，除非首先考虑环境条件，否则很难确定盈利的管理实践。当作物管理实践根据降雨量和播种日期进行调整以最大限度地提高毛利率时，产量比工业实现的平均产量高 2 Mg ha-1。随着可变成本的增加，收益率普遍增加，但毛利率趋于稳定；在此之后，更高的可变投入成本与更高的收益相匹配，但未超过收益增加。毛利率因个人管理因素而变化：对于播种日期，毛利率随着 3 月中旬开始逐渐推迟播种而下降。对于所有播种日期的氮肥施用量，在降雨量较高的十分位数上使用较高的氮肥施用量，而在播种延迟时使用较低的氮肥施用量更有利可图。除了降雨量低的地区（低降雨量十分位点或低降雨量地区的地区）外，具有缓慢至中等发育速度的品种在 4 月底之前的早期播种中最有利可图。杂交品种和传统的开放授粉品种的毛利率相似，由于其较低的产量潜力，这比耐三嗪的开放授粉品种更大。通过了解季节性降雨量，可以选择最有利可图的做法，但可以选择与发育速度相匹配的播种时间和非 TT-OP 品种，以在不了解降雨量的情况下最大化毛利率。然而，高昂的生产成本可能会阻碍最有利可图的管理实践选择。