MANAGEMENT OF PRIMOCANE-FRUITING BLACKBERRY TO MAXIMIZE YIELD AND EXTEND THE FRUITING SEASON

Abstract

'Prime-Jan' and 'Prime-Jim' were studied in a field planting established in June 2003 in Aurora, Ore., USA. Primocane management treatments studied were: 1) primocane-only cropping with no manipulation [un-tipped]; 2) double cropping with no primocane manipulation [primocane + floricane crop]; 3) primocanes soft-tipped at 1 m to encourage branching; and 4) rowcovers used in late-winter to early-spring to advance primocane growth; treatments 1, 3, and 4 were a primocane crop only. 'Prime-Jan' had a higher floricane yield than 'Prime-Jim' (6.1 vs. 4.0 t/ha), but a smaller berry size (4.0 vs. 4.6 g; P ≤ 0.01). Primocanes that grew in the presence of floricanes were significantly longer (2.5 m) than un-tipped canes (2.1 m) in both cultivars. On average, the un-tipped primocanes of 'Prime-Jan' were shorter than those of 'Prime-Jim'. On 14 July 2004, primocanes in most treatments were just starting to flower and fruit harvest began on 16 Aug. Use of rowcovers in 2005, advanced bloom 14 d (24 June) compared to un-tipped canes. The 50% yield date was 7-14 Sept. for 'Prime-Jim', depending on treatment and 14 Sept. for 'Prime-Jan'. Rowcovers increased yield, compared to un-tipped, non-covered plots. Soft-tipped primocanes had up to three fold the yield of un-tipped canes (5.2 vs. 1.8 t/ha). We stopped picking in mid-Oct. due to poor weather, but at that time there were still flower buds, flowers, and un-ripe fruit present on most treatments.