Drip irrigation has rapidly become the most popular method to irrigate blueberry in most countries, including the United States and Canada. Young plants often grow better with drip than with conventional sprinkler systems and, as a result, produce more fruit with much less water during the first year or 2 after planting (Bryla, 2008; Bryla et al., 2009, 2011). However, there is little information currently available on the use of drip in mature plantings.
Canopy cover increases rapidly in blueberry and, therefore, results in much greater water use in older plantings. Holzapfel et al. (2004) found that the amount of water required for maximum production of blueberries nearly doubled between the second and seventh year after planting in Chile. The water use in the planting may also increase with cropload. Bryla and Strik (2007) found that water use in ‘Duke’ was as high as 70 mm/week in early June, before the beginning of harvest, but dropped quickly to 40 mm/week per week in late July, after harvest. Mingeau et al. (2001) found a similar decline in water use after harvest in ‘Bluecrop’ blueberry grown in containers. Thus, it is not unreasonable to expect that older plants with larger croploads will have greater water requirements.
The response of blueberry plants to the frequency of irrigation may also change as the planting matures. Blueberry is a shallow-rooted crop with most of its root system confined typically to the top 0.5 m of soil. In a 5-year-old planting in Oregon, more than 90% of the fine roots were located at less than 0.3 m, and the highest density of roots were between 0.10 and 0.2 m (Bryla and Strik, 2007). Consequently, unlike many deeper-rooted plants, blueberry tends to use its available soil water quickly compared with most perennial crops and, therefore, requires frequent rain or irrigation to avoid water stress (Bryla, 2011).
In a recent study in the Fraser Valley of British Columbia, we found that plant growth and yield of ‘Duke’ blueberry were unaffected by irrigation rates of 5 L/plant and 10 L/plant applied several times per week compared with zero irrigation during the first 3 years after planting and was only greater with drip irrigation during the fourth year (Ehret et al., 2012). However, several fruit quality characteristics such as fruit size, firmness, and soluble solids concentration were affected a year or 2 earlier by irrigation, but neither yield nor fruit quality was affected by the configurations of the drip system in any year. The present study is a continuation of this previous work. The objective was to determine if the trends observed in the younger plants changed over time as the planting matured.
BCMAL 2009 Berry production guide. BC Ministry of Agriculture and Lands, Victoria, BC, Canada
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