Effects of spatial and temporal regulation of drip emitters and tube configurations on water productivity of juvenile macadamia trees in the tropics

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