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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Research Unit » Research » Publications at this Location » Publication #165039


item Bryla, David

Submitted to: Acta Horticulturae International Symposium on Vaccinium Culture
Publication Type: Proceedings
Publication Acceptance Date: 9/17/2005
Publication Date: 8/31/2006
Citation: Bryla, D.R., Strik, B.C. 2006. Variation in plant and soil water relations among irrigated blueberry cultivars planted at two distinct in-row spacings. Acta Horticulturae International Symposium on Vaccinium Culture. 715:295-300.

Interpretive Summary: Highbush blueberry is a shallow-rooted crop that is highly sensitive to soil water deficits. Despite this vulnerability, little is known about the water relations of the crop, particularly with regard to any variation that may occur among cultivars or with cultural practices. More information on blueberry water relations is needed to help develop better water management practices for the crop. With rising production costs, many blueberry growers in the region are beginning to space plants closer together to increase early productivity and improve machine-harvest efficiency. We conducted a study to determine the effect of plant spacing on water use by three popular cultivars of blueberry commonly grown in the Pacific Northwest. Water use was measured on plants spaced at either close or traditional spacing, and possible mechanisms that enhance the ability of the cultivars to tolerate short-term episodes of soil water deficit were identified. Overall, the results indicated that although close spacing reduced individual plant size, significantly more water was required when plants were spaced close together than when they were spaced further apart due to increased canopy cover. The results also showed considerable variation among cultivars to tolerate short-term episodes of water deficit. This was due to differences in the size of the root systems or the ability to maintain plant water status, both of which influence the amount and frequency of irrigation required by each cultivar throughout the growing season.

Technical Abstract: A study was conducted to determine the effect of in-row spacing on plant and soil water relations in 'Duke', 'Bluecrop', and 'Elliott' highbush blueberry and to identify possible mechanisms that may enhance the ability of these cultivars to tolerate short-term soil water deficits. Four years after planting, changes in soil water content, stem water potential, and leaf stomatal conductance were measured on well-irrigated plants of each cultivar spaced 0.5 or 1.2 m within rows and 3.0 m between rows. Irrigation was applied equally to all treatments by overhead sprinklers during the dry summer months from mid-May to early-September. Close spacing significantly reduced individual shoot dry weight, but also significantly increased crop light interception and water uptake from 0-0.6 m soil depth compared to plants spaced further apart. Spacing had little effect, however, on plant water relations. Independent of cultivar and spacing, stomatal conductance decreased rapidly as stem water potential approached -0.6 to -0.8 MPa. Among cultivars, 'Bluecrop' had the lowest root mass and root:shoot dry weight ratio at either spacing, while 'Elliott' had the highest. 'Duke', in comparison, produced the deepest root system, extracting a significant amount of water below 0.6 m when plants were closely spaced. 'Duke' also maintained, on average, higher stem water potentials and greater stomatal conductance than the other cultivars as soil water was depleted.