High Tunnel versus Open Field: Management of Primocane-fruiting Blackberry Using Pruning and Tipping to Increase Yield and Extend the Fruiting Season

Abstract

<jats:p>Primocane-fruiting blackberries (<jats:italic>Rubus</jats:italic> subgenus <jats:italic>Rubus</jats:italic> Watson) may offer opportunities for season extension and off-season fruit production, particularly in mild climates with protected culture. In May 2005, plants of ‘Prime-Jan’® were established at the Oregon State University–North Willamette Research and Extension Center, Aurora, OR. Half of the planting was established under a high tunnel and the remainder planted in an adjacent open field. In 2006 to 2007, primocanes were subjected to four treatments to promote branching and/or delay harvest: 1) all primocanes within the plot were cut to the ground when averaging 0.25 m tall, then later emerging canes soft-tipped when reaching 0.5 m tall (C0.25m/T0.5m); 2) all primocanes within the plot were cut to the ground when averaging 0.5 m tall, then later emerging canes soft-tipped when reaching 0.5 m (C0.5m/T0.5m); 3) primocanes double-tipped: all primocanes within the plot were soft-tipped when averaging 0.5 m tall with subsequent lateral branches then soft-tipped when reaching 0.5 m long (T0.5m/Tb0.5m); and 4) primocanes were soft-tipped when averaging 0.5 m tall (T0.5m; control). The tunnel was covered with plastic from 5 Sept. 2006 and 31 Aug. 2007, ≈1 to 2 weeks before harvest until the end of harvest to protect fruit from inclement weather. On average, fruit harvest began on 12 Sept. in the open field and tunnel, but lasted ≈3 weeks longer in the tunnel, ending on 16 Nov., on average. Primocanes that were double-tipped had nearly twice the flowers and fruit than canes that were soft-tipped only once (T0.5m; control). In the tunnel, cumulative yield of double-tipped primocanes averaged 10.7 t·ha<jats:sup>−1</jats:sup> in 2006 and 19.3 t·ha<jats:sup>−1</jats:sup> in 2007, a 267% and 159% increase compared with the control, respectively. On average, cumulative yield for all treatments was less in the open field than in the tunnel, although cultural systems could not be compared statistically. Harvest was not delayed in the C0.25m/T0.5m treatment in 2006 compared with the control and the double-tipped treatments; however, in 2007, harvest was delayed by 2 weeks in C0.25m/T0.5m. In contrast, harvest was delayed by ≈4 weeks when primocanes were cut to the ground at 0.5 m (C0.5m/T0.5m). Primocanes that were double-tipped produced heavier fruit than other treatments (33% heavier than the control, on average). Double-tipped primocanes did not have more ovules per flower, but had significantly more drupelets set compared with the control. In addition, plants growing under the tunnel tended to produce heavier fruit (32%, on average) than those grown in the open field. Harvest date affected fruit pH in 2006, but not in 2007. In 2006, fruit pH was highest in the early season. All other differences in fruit chemistry were not significant. The pruning and tipping systems used here increased yield and offered options for season extension.</jats:p>

Blackberry Production Systems - A Worldwide Perspective

“…Soft-tipping the primocane of annual blackberries at 1 m induced branching and increased flower and fruit number and yield three-fold without affecting fruiting season . A double-tip, where branches are further shortened, has been shown to increase yield (Thompson et al, 2009). Genotype, rate of flowering, and climate may affect best pruning methods (Strik, personal observation).…”

“…Use of spunbound row covers from late winter, before primocane emergence, through ~0.6 m primocane height advanced flowering and fruiting by two weeks in Oregon , but had no impact in North Carolina, USA (Fernandez and Ballington, 2010). In plants where primocanes were mowed back to ground level when height averaged ~0.5 m, fruit production was delayed by about four weeks (Thompson et al, 2009). Producing primocane-fruiting blackberry in an un-heated tunnel extended the harvest season about three weeks in Oregon's temperate climate (Thompson et al, 2009).…”

“…In plants where primocanes were mowed back to ground level when height averaged ~0.5 m, fruit production was delayed by about four weeks (Thompson et al, 2009). Producing primocane-fruiting blackberry in an un-heated tunnel extended the harvest season about three weeks in Oregon's temperate climate (Thompson et al, 2009). Growth and production ceased due to cool night temperatures even though there were many flower buds, flowers, and immature fruit present (Strik, pers.…”

The Impact of Severity and Time of Tipping and Hedging on Performance of Primocane-fruiting Blackberry in a Tunnel

“…The hard-hedging treatments may have performed better if they had been done earlier or at the same time as the soft-hedging treatments; this would only have been possible if canes had been cut back (hedged) to a shorter height than 1 m on week 1. Thompson et al (2009) found that canes tipped as short at 0.5 m produced high yield. It is also possible that when plots were hedged, some canes were tipped that had already produced flower buds; this would have led to a reduction in yield/plot (Drake and Clark, 2003;B.C.…”

“…S oft-tipping (removal of 2-5 cm) primocane-blackberry canes once (Drake and Clark, 2003;Strik et al, 2008 andThompson et al, 2009) or double-tipping (main cane and branches; Thompson et al, 2009) has been shown to increase yield compared with untipped canes and has become standard industry practice (B.C. Strik, personal observation).…”