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

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Bhattarai, S. P., Pendergast, L., Shuyan, L. and Midmore, D. J. (2021) Effects of spatial and temporal regulation of drip emitters and tube configurations on water productivity of juvenile macadamia trees in the tropics. Experimental Agriculture, 57 (5-6). pp. 338-351. ISSN 0014-4797

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Article Link(s): https://doi.org/10.1017/S0014479722000011

Abstract

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.

Item Type:Article
Business groups:Crop and Food Science
Additional Information:Open access
Keywords:Deficit irrigation Drip irrigation Emitter control Variable flow Root length density Growth Nut count Single in-line tube Double in-line tube
Subjects:Agriculture > Agriculture (General) > Agricultural meteorology. Crops and climate
Agriculture > Agriculture (General) > Improvement, reclamation, fertilisation, irrigation etc., of lands (Melioration)
Plant culture > Tree crops
Plant culture > Food crops
Plant culture > Fruit and fruit culture > Nuts
Agriculture > By region or country > Australia > Queensland
Deposited On:15 Mar 2022 05:46
Last Modified:15 Mar 2022 05:46

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