Timing irrigation to suit citrus phenology: a means of reducing water use without compromising fruit yield and quality?
R. J. Hutton A C , J. J. Landsberg A and B. G. Sutton BA National Wine and Grape Industry Centre, (NSW Department of Primary Industries and Charles Sturt University), Locked Bag 588, Wagga Wagga, NSW 2768, Australia.
B The University of Sydney, Faculty of Agriculture Food and Natural Resources, McMillan Building (AO5), Sydney, NSW 2006, Australia.
C Corresponding author. Email: ron.hutton@dpi.nsw.gov.au
Australian Journal of Experimental Agriculture 47(1) 71-80 https://doi.org/10.1071/EA05233
Submitted: 1 September 2005 Accepted: 26 July 2006 Published: 2 January 2007
Abstract
This paper addresses the question of whether a citrus crop has the same need for water at all stages of development or whether it is possible to withhold water at times when the crop is less sensitive to water stress, thus, reducing total water use and improving water use efficiency while still maintaining yield. To answer this question water applied by irrigation was reduced by up to 33% relative to standard full irrigation by extending the intervals between applications from 3 to 17 days during fruit growth stages II and III in the annual growth cycle. As expected, the longer intervals resulted in greater depletion in soil moisture and significant water stress developed as soil water deficits approached the lower limits of plant available water. Stressed trees exhibited mean pre-dawn water potential (ψl) values of –0.93 MPa and midday ψl values decreased to between –2.0 and –2.5 MPa. Periodic soil water deficits in late summer and autumn reduced shoot growth, but fruit yield was unaffected, and there was no evidence of reduced canopy size. Water use efficiency (mass of fruit produced per unit water applied) improved, but fruit growth was extremely sensitive to moisture stress and extended irrigation intervals in summer and autumn reduced fruit size. Fruit juice quality was also affected, as there was an increase in both total soluble solids and juice acidity, but the practical consequences of these were limited because there were only small changes to the sugar : acid ratios. This work has demonstrated that deficient irrigation during summer can be used to manipulate growth and reduce water use, but at the risk of a marginal reduction in fruit size.
Additional keywords: citrus phenology, fruit yield and quality, irrigation intervals, soil water deficit, water stress.
Acknowledgements
The authors thank NSW Department of Primary Industries for the provision of staff and resources to support the work described in this paper. Likewise, the funding support from HAL (formerly HRDC), NRMS (Murray–Darling Basin Commission) and NPIRD (Land and Water Australia), Leeton Citrus Growers Association, Griffith Citrus Growers’ Association, Murray Valley Citrus Marketing Board, and Berri Fruit Juices (formerly Leeton Citrus Juices) is gratefully acknowledged. We also gratefully acknowledge the valuable assistance offered by management, technical and farm support staff of the Yanco Agricultural Institute who assisted in field site operations, maintenance and data collection. Special thanks must also be extended to Dr Ken Bevington and Dr Neil Coombes (NSW Department of Primary Industries) and Dr Brian Loveys (CSIRO Horticulture), who worked collaboratively with us on associated industry funded projects.
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