Canola (Brassicanapus L.) growth and yield can be enhanced by, amongst others, choosing the correct rate, source, and timing of N fertilizer. Limited research exists on the effects of nitrogen (N) source on canola growth and yield properties when grown under conservation agriculture. This study compared the performance of different N fertilizer sources on canola biomass production, seed yield, and oil content. Field trials were conducted from 2016 to 2019 at five sites in the Western Cape Province of South Africa which is characterized by a Mediterranean climate. Nitrogen fertilizer source had no effect (p > .05) on biomass production or oil content at any site. Sufficient soil water levels and warm daily temperatures led to greater biomass production regardless of nitrogen source. Oil content was determined by the presence of rainfall during the flowering and seed filling stages. The effect of N source on yield varied among sites in accordance with timing of fertilizer application in relation to rainfall. The urea + urease inhibitor N source led to greater (p < .05) yields than the urea N source without the inhibitor at the Darling site, regardless of the soil water conditions. Mean yield values of all seasons and sites indicated that urea + urease inhibitor fertilizer to be the most reliable N source to ensure optimal yields over the long-term.

中文翻译：

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氮源对南非保护性农业种植的油菜（Brassica napus L.）的影响

Canola ( Brassicanapus L.) 的生长和产量可以通过选择正确的氮肥比例、来源和时间等来提高。在保护性农业下种植时，氮 (N) 源对油菜生长和产量特性的影响的研究有限。本研究比较了不同氮肥来源对双低油菜籽生物量生产、种子产量和含油量的影响。田间试验于 2016 年至 2019 年在以地中海气候为特征的南非西开普省的五个地点进行。氮肥来源无影响（p > .05) 任何地点的生物质产量或含油量。无论氮源如何，充足的土壤水位和温暖的日常温度都会导致更高的生物量产量。油含量由开花和种子灌浆阶段降雨的存在决定。氮源对产量的影响因施肥时间与降雨量的关系而异。 在 Darling 地点，尿素 + 尿素酶抑制剂氮源比没有抑制剂的尿素氮源产生更高的 ( p < .05) 产量，无论土壤水分条件如何。所有季节和地点的平均产量值表明，尿素 + 尿素酶抑制剂肥料是最可靠的氮源，可确保长期获得最佳产量。