Efforts to optimise inputs for irrigated cotton production are ongoing. Nitrogen use efficiency is influenced by crop management, climate and water availability. Recent research in southern NSW, Australia, reported minimal interaction between irrigation strategies and nitrogen rates. Similar work is lacking from other cotton growing locations and soil types. This study investigated the interaction of nitrogen rates and various deficit-triggered irrigation strategies on cotton lint yield, and nitrogen/water use efficiencies at locations differing to previous studies in climate, day degree accumulation and soil type. Four field experiments were conducted at two locations across four seasons (2015–2018). All experiments were split-plot design with irrigation strategies as the main plot and nitrogen fertiliser rates as subplots. The study explored the synergistic effects of varying rates of (i) nitrogen fertiliser (range: 0–360 kg N/ha) and (ii) irrigation frequency (high, moderate, and low frequencies triggered using plant available water deficits of 50, 70, and 100 mm, respectively) on the growth of cotton, lint yield, nitrogen use efficiency (NUE), and water use efficiency (WUE). A moderate irrigation frequency (70 mm deficit) and nitrogen fertiliser rate (∼150 kg N/ha) improved WUE and NUE compared to more frequent irrigation (50 mm deficit) and high nitrogen fertiliser (>300 kg N/ha), but did not increase lint yields. The high-frequency irrigation, combined with a high nitrogen fertiliser strategy, resulted in taller plants with more nodes but reduced fruit retention below the 15th node. This approach promoted early-season vegetative growth at the expense of fruiting retention and thus reduced harvest index. There was no consistent interaction between irrigation frequency and nitrogen fertiliser rate on cotton lint yield, plant dry matter or nitrogen uptake across all four experiments. High frequency irrigation and high nitrogen fertiliser rates maximised vegetative growth but not cotton lint yield. More moderate water and nitrogen strategies gave similar lint yields but greater nitrogen and water use efficiency. Cotton growers can maximise production without the need for excessive inputs of nitrogen and water that may be environmentally detrimental and economically wasteful.

中文翻译：

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效率胜过过剩：通过最佳灌溉和氮肥施用最大化皮棉产量


优化灌溉棉花生产投入的努力仍在继续。氮肥利用效率受到作物管理、气候和水资源供应的影响。澳大利亚新南威尔士州南部的最新研究表明，灌溉策略与施氮量之间的相互作用极小。其他棉花种植地点和土壤类型缺乏类似的工作。本研究调查了施氮量和各种赤字触发的灌溉策略对皮棉产量和氮/水利用效率的相互作用，该研究与之前在气候、日度积累和土壤类型方面的研究不同。在四个季节（2015-2018）的两个地点进行了四次现场实验。所有试验均采用裂区设计，以灌溉策略为主区，氮肥施用量为次区。该研究探讨了不同施用量（i）氮肥（范围：0-360kgN/ha）和（ii）灌溉频率（使用植物可用水不足 50、70 触发的高、中和低频率）的协同效应。和100mm）对棉花生长、皮棉产量、氮肥利用效率（NUE）和水分利用效率（WUE）的影响。与更频繁的灌溉（50毫米赤字）和高氮肥（> 300公斤N /公顷）相比，适度的灌溉频率（70毫米赤字）和氮肥施用量（〜150公斤N /公顷）改善了WUE和NUE，但不会增加皮棉产量。高频灌溉与高氮肥策略相结合，导致植株更高、节数更多，但第 15 个节点以下的果实保留率降低。这种方法促进了早季营养生长，但牺牲了果实保留，从而降低了收获指数。 在所有四个实验中，灌溉频率和氮肥用量对皮棉产量、植物干物质或氮吸收之间没有一致的相互作用。高频灌溉和高氮肥用量最大化了营养生长，但没有最大化皮棉产量。更温和的水和氮策略产生相似的皮棉产量，但氮和水的利用效率更高。棉花种植者可以最大限度地提高产量，而无需过量投入氮和水，这可能对环境有害并且在经济上造成浪费。