Macadamia in Australia is traditionally grown in semi-arid climates with hot and humid summers and cool winters supporting rainfed cultivation. Recent industry expansion into more northern, drier production areas of Queensland, Australia, requires supplementary irrigation for successful macadamia production. However, ever-increasing demand for irrigation water in these areas is both competitive and regulated. Limited information is available to optimize water use efficiency for field-grown macadamia trees. We trialled a technique that employs specially designed drip tubes with push-in emitter plugs to close emitters so that transplanting can start with emitters closed distant from tree bases and open next to the trunks of each tree. Additional emitters are then gradually opened (i.e., plugs are removed) as tree canopy size increases over subsequent years. This technique was tested on single and double in-line irrigation tube configurations per row of macadamia. Temporal regulation of emitter closure significantly reduced irrigation input by 75, 50 and 25% in the first, second and third year of treatment. Hence, irrigation over the three-year establishment period was reduced to one-half that of the non-regulated crop. These early reductions of irrigation in juvenile trees had no significant negative effects on plant growth (height, canopy spread, leaf chlorophyll and leaf photosynthetic rates), nor on nut counts. Control of emitter discharge between the plants along the row in the earlier stage (i.e., before complete within-row canopy cover) also reduced weed growth between the trees in the row. Notable growth advantages of the single in-line over the double in-line tube configuration were evident, with a non-significant but sizeable benefit on nut counts too. Effects of the temporal regulation of emitters and of in-line tube configurations must be validated on cultivars with differing water requirements and for the longer-term reproductive performance and nut quality.

澳大利亚的澳洲坚果传统上生长在半干旱气候中，夏季炎热潮湿，冬季凉爽，支持雨养种植。最近的工业扩展到澳大利亚昆士兰更北部、更干燥的生产区，需要补充灌溉才能成功生产澳洲坚果。然而，这些地区对灌溉用水不断增长的需求既具有竞争力，又受到监管。有限的信息可用于优化田间种植的澳洲坚果树的用水效率。我们试验了一种技术，该技术采用带有推入式发射器插头的特殊设计的滴管来关闭发射器，以便移植可以从远离树基的发射器开始并在每棵树的树干旁边打开。然后逐渐打开额外的发射器（即，插头被移除）随着树冠尺寸在随后几年中的增加。该技术在每排澳洲坚果的单和双在线灌溉管配置上进行了测试。在处理的第一年、第二年和第三年，对灌水器关闭的时间调节显着减少了 75%、50% 和 25% 的灌溉投入。因此，三年种植期的灌溉量减少到非管制作物的一半。幼树灌溉的这些早期减少对植物生长（高度、树冠蔓延、叶绿素和叶片光合速率）以及坚果数量没有显着的负面影响。在早期阶段（即在完全行内冠层覆盖之前）控制沿行植物之间的发射器排放也减少了行中树木之间的杂草生长。单直列式比双列直列式管配置的显着增长优势是显而易见的，对螺母数量也有不显着但相当大的好处。必须在具有不同需水量的品种以及长期繁殖性能和坚果质量上验证发射器和在线管配置的时间调节的影响。