The following pruning treatments were studied in mature 'Bluecropʼ (1996)(1997)(1998)(1999)(2000) and 'Berkeleyʼ (1996-98) plants: 1) "conventional" pruning with removal of unproductive canes, thinning of 1-year-old shoots at the base of the bush, and removal of any unproductive wood or thinning of excessive fruiting wood near the top of the bush, as required; 2) "speed" pruning involving removal of one or two of the most unproductive canes at the base of the bush; and 3) "un-pruned" where no pruning was done for the length of this study. Conventional pruning took an average of 6.4 min/plot, while speed pruning saved 88.8% time. There was no pruning treatment effect on the percentage of fruit buds in 'Berkeleyʼ (42%) or 'Bluecropʼ (34%) or percent fruit set (70% to 90%, depending on cultivar and year) in any year. Un-pruned plants of both cultivars had signifi cantly greater yield than conventionally pruned plants, depending on the year, while speed pruning generally resulted in intermediate yields. Un-pruned and speed-pruned plants produced berries that were 19% to 27% smaller than conventionally pruned plants, depending on year. The fruit harvest season of un-pruned plants began 3 to 5 days later and lasted a week longer than that of conventionally pruned plants. The harvest effi ciency of un-pruned plants was reduced as much as 51% in the later years of this study and was most closely correlated with berry weight. Conventionally pruned plants had a signifi cantly higher percentage of the above-ground dry weight allocated to 1-year-old wood and crown than un-pruned plants. In 'Bluecropʼ, N concentration tended to be higher in the crown of conventionally pruned plants than in un-pruned or speed-pruned plants. Conventionally pruned 'Bluecropʼ plants had signifi cantly higher concentrations of K and P and lower N than un-pruned plants and 'Berkeleyʼ had lower concentrations of N, than un-pruned plants. Results indicate that not pruning mature plants may be an option in the short-term, but may have undesirable effects for long-term sustainability.

The effect of early cropping (no removal of fruit buds the first two years) and in-row spacing (0.45 or 1.2 m) on growth and yield of `Duke', `Bluecrop', and `Elliott' northern highbush blueberries (Vaccinium corymbosum L.) was studied. Plants were grown on raised beds for four years. No yield was produced on the control plants in the planting year (year 1) and year 2. Plant growth at the start of year 3 was adversely impacted by early cropping in years 1 and 2. Early cropping reduced the dry weight of the root system, crown, and 1- to 3-year-old wood in all cultivars. `Bluecrop' plants had less total dry weight than those of `Duke' or `Elliott'. Roots accounted for 30% to 45% of the total plant dry weight depending on cultivar. Early-cropped plants had a lower percentage of fruit buds than control plants. Early cropping reduced yield 44%, 24%, and 19% in year 3, compared to control plants, in `Elliott', `Duke', and `Bluecrop', respectively. Cumulative yield (years 1 through 4) was similar between control and early cropped plants in `Bluecrop' and `Duke', whereas early cropping reduced cumulative yield in `Elliott' 20% to 40%, depending on in-row spacing. Plants spaced at 0.45 m produced 62% to 140% more yield per hectare than those spaced at 1.2 m, depending on cultivar. `Elliott' plants seemed less suited to high density planting due to their large root system.

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 Jun-tipped]; 2) double cropping with no primocane manipulation Iprimocane + floricane crop]; 3) primocanes "softtipped" 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 (23 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. Softtipped primocanes had up to three fold the yield of un-tipped canes (5.2 vs. 1.8 tiha). 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.

No abstract

Fertilizer nitrogen (FN) recovery, and changes in nitrogen (N) and dry weight partitioning were studied over three fruiting seasons in June-bearing strawberry (Fragaria ×ananassa Duch. `Totem') grown in a matted row system. Fertilizer nitrogen treatments were initiated in 1999, the year after planting. The standard ammonium nitrate N application at renovation (55 kg·ha-1 of N) was compared to treatments where additional N was applied. Supplemental treatments included both ground-applied granular ammonium nitrate (28 kg·ha-1 of N) applied early in the season and foliar urea [5% (weight/volume); 16 kg·ha-1 of N] applied early in the season and after renovation. When labeled N was applied (eight of nine treatments) it was applied only once. The impact of no FN from the second through the third fruiting season was also evaluated. Fertilizer nitrogen treatment had no impact on total plant dry weight, total plant N, yield or fruit quality from the first through the third fruiting seasons. Net dry matter accumulation in the first fruiting season was 2 t·ha-1 not including the 4 t·ha-1 of dry matter removed when leaves were mowed during the renovation process. Seasonal plant dry weight and N accumulation decreased as the planting aged. Net nitrogen accumulation was estimated at 40 kg·ha-1 from spring growth to dormancy in the first fruiting season (including 30 kg·ha-1 in harvested fruit, but not including the 52 kg·ha-1 of N lost at renovation). Recovery of fertilizer N ranged from 42% to 63% for the broadcast granular applications and 15% to 52% for the foliar FN applications, depending on rate and timing. Fertilizer N from spring applications (granular or foliar) was predominantly partitioned to leaves and reproductive tissues. A large portion of the spring applied FN was lost when plants were mowed at renovation. Maximum fertilizer use efficiency was 42% for a granular 55 kg·ha-1 application at renovation, but declined to 42% just before plant growth the following spring, likely a result of FN loss in leaves that senesced. In June, ≈30% of the N in strawberry plants was derived from FN that was applied at renovation the previous season, depending on year. This stored FN was reallocated to reproductive tissues (22% to 35%) and leaves (43% to 53%), depending on year. Applying fertilizer after renovation increased the amount of remobilized N to new growth the following spring. The following June, 15% of plant nitrogen was derived from fertilizer applied at renovation 2 years prior.