Four organic fertilizers were evaluated in a commercial lowbush blueberry field with a history of N and P deficiency. In nonorganic production, diammonium phosphate (DAP) is the standard fertilizer for correcting N and P deficiency. Nitrogen a rate of 67 kg·ha-1 [Renaissance (8-2-6), ProHolly (4-6-4), Pro Grow (5-3-4), Nutri-Wave (4-1-2), or DAP (18-46-0)] was applied preemergent to 1.8-m × 15-m treatment plots. Leaf N and P were deficient (<1.6% and 0.125%, for N and P, respectively) in the unfertilized plots that served as controls. DAP and Pro-Holly raised leaf N to satisfactory levels (>1.6%). Only DAP raised leaf P concentrations (0.144%), compared to controls (0.122%). Leaf K was not deficient, but was raised by Pro-Holly. Soil pH was slightly lowered by Renaissance (4.2) and raised by Pro-Holly (4.4), compared to the control (4.3). Soil P concentrations were raised by DAP and soil S by Pro-Holly. Soil K was raised by all fertilizers except DAP, compared to the control. Pro-Holly and DAP were equally effective in increasing stem height, branching, branch length, flower bud formation, and yield, compared to the control and the other organic fertilizers. Pro-Holly could effectively substitute for DAP in organic wild blueberry production.
Experimental plots in a commercial lowbush blueberry (Vaccinium angustifolium Ait.) field deficient in N and P received preemergent 33.6 and 67.2 kg/ha rates of N (urea), P (23 % phosphoric acid), N+P (DAP), N+P+K (S-10-5) or N+P+K (fish hydrolysate, 2-4-2). A RCB design with eight replications of 12 treatments was used. Fertilizer containing N alone was as effective in raising N leaf concentrations, as those containing N and P. However, leaf phosphorus concentrations were raised more by fertilizer providing N and P than only P. Fish hydrolysate fertilizer was as effective as 5-10-5 in raising leaf N, P and K concentrations in prune and crop year leaf samples.
Acetaldehyde is a metabolite frequently attributed a key role in physiological deterioration of fruits and other plant materials. In fruits, it accumulates during ripening and during development of many physiological disorders. Its role in deterioration, however, is not clear. Its toxicity is easily demonstrated, hence it is tempting to ascribe injury and degeneration to acetaldehyde accumulation. Nevertheless, a body of evidence suggests that its accumulation is a result, rather than cause, of tissue disorganization. Resolution of this question awaits development of an analytical method that will overcome the deficiencies inherent in methods used in the past.
In three commercial fields with a history of low leaf P concentrations, triple super phosphate (TSP) (1 P: 0 N), monoammonium phosphate (MAP) (2.1 P: 1 N), and diammonium phosphate (DAP) (1.11 P: 1 N) with P at 67.2 kg·ha-1 were compared to a control in a randomized complete-block design with 12 blocks. In 1995, all fertilizer treatments were comparable in raising soil P concentrations, but MAP and DAP resulted in higher P leaf concentrations compared to the control. DAP was more effective than MAP in raising N leaf concentrations. Leaf concentrations of Mg, B, and Cu were lowered by MAP and DAP but not TSP. Stem density, stem length, flower buds per stem, flower bud density, and yield were raised by DAP. The same treatments were applied in May 1997 and in May 1999 to the same plots in the same fields. In 1997, by the time of tip dieback in the prune year of that cycle, foliar concentration of P and N averaged higher than in the previous cycle, but still were not up to the standard for N. Fruit yield for the second cycle averaged substantially higher for the controls and for all three treatments, most dramatically for the DAP. In 1999, with only two fields available, response to treatments depended on soil N availability. At the field where leaf N was lower in control plots, MAP and DAP were more effective than TSP in raising leaf P.
For accelerating the filling in of bare areas in native lowbush blueberry fields or converting new areas to production, micropropagated plantlets rooted after three subcultures outperformed seedlings and rooted softwood cuttings. After 2 years of field growth, they averaged 20.3 rhizomes each of average dry weight 3.5 g, as compared with 5.7 rhizomes of average dry weight 1.1 g for rooted softwood cuttings. After 1 year of field growth, seedlings produced on average 3.3 vs. 0.4 rhizomes from micropropagated plants that had not been subcultured and 0.3 rhizomes from stem cuttings. Apparently, subculturing on cytokinin-rich media induces the juvenile branching characteristic that provides micropropagated plants with the desirable morphologies and growth habits of seedlings. These characteristics favor rhizome production while the benefits of asexual reproduction are retained. The advantage in rhizome production of micropropagation over stem cuttings varied among clones.
A new method for analyzing acetaldehyde concentration in apple (Malus domestica Borkh.) tissues was used to measure its accumulation in senescing fruits. Initially low levels (1 µg/g fresh weight) increased as the fruits ripened, but only at advanced senescence did they reach relatively high levels (14 µg/g fresh weight). Acetaldehyde did not accumulate in advance of tissue disorganization. Watercored ‘Delicious’ apple tissue accumulated significantly more acetaldehyde than tissue of non-watercored fruits during storage, but watercore breakdown did not result. There was no consistent difference in acetaldehyde levels of ethephon-treated and non-treated ‘McIntosh’ apples after long-term storage, although the ethephon-treated fruits developed more senescent breakdown. However, the acetaldehyde level in fruits after breakdown occurred was about 20% higher than that in corresponding sound fruit. Acetaldehyde accumulation appeared to be a consequence of tissue disorganization rather than a cause of senescent breakdown in the fruits.
Cuttings of 2 clones of lowbush blueberry (Vaccinium angustifolium Ait.) treated with increasing rates of urea (0, 40, 80 kg N/ha) during rooting resulted in increased levels of total stem nitrogen in the respective treatments. Fall flowering and vegetative growth of cuttings in the propagation beds were stimulated by nitrogen treatments. Plants moved to cold storage (5°C) for 3 months and then grown under long day (16 hours) greenhouse conditions for 2 months did not produce more rhizomes in response to nitrogen treatments. However, plants which remained in the propagation beds during the winter and which were grown under field conditions for 6 months, responded to the nitrogen treatments by producing larger root systems, more aerial growth and more rhizomes.
Fertilization with 98 and 196 kg N/ha from urea or sulfur-coated urea (SCU) resulted in higher amounts of K2SO4-extractable ammonium N in the 0-7.6 cm but not the 7.6-15.2 cm soil layer. There was no difference due to sources of N. Application of 98 kg N/ha from either urea or SCU to portions of 5 clones of lowbush blueberry (Vaccinium augustifolium Ait.) increased N concentration, size and weight of leaves, flower bud formation, and yield.
Stem cuttings were harvested in April from four clones of containerized bunchberry(Cornus canadensis L.) forced in the greenhouse and in June from the same four clones growing in the field. April cuttings that had produced rhizomes by transplant time produced the greatest mean number and weight of shoots during the first growing season compared to April cuttings without rhizomes, June cuttings with rhizomes, or June cuttings without rhizomes. In a second study, cuttings and single-stem divisions were taken in July; divisions produced a greater mean number of shoots than did stem cuttings when compared at the end of Oct. A third study evaluated the effect of K-IBA application to lateral buds on subsequent rhizome production, and the effect of cutting node number (two vs. three nodes) on root or rhizome development. Treating lateral buds with K-IBA was not inhibitory to rhizome formation and elongation. Compared to two-node cuttings, three-node cuttings produced greater mean rootball size, rhizome number, and rhizome length; nearly twice as many of the three-node cuttings formed rhizomes as did two-node cuttings. A fourth study showed that cuttings rooted for 5 or 6 weeks in a mist enclosure generally exhibited greater shoot and rhizome production by the end of the first growing season than cuttings rooted for 8 or 9 weeks. This was despite the finding that cuttings rooted for longer durations (8 or 9 weeks) possessed larger rootballs and greater rhizome numbers at transplant time compared to cuttings rooted for shorter durations (5 to 6 weeks). Chemical name used: indole-3-butyric acid (K-IBA).
Twenty stems with four fruit buds were tagged in each of ten lowbush blueberry (Vaccinium angustifolium Ait.) clones in a commercial field to assess fruit set and fruit size and weight characteristics. The terminal bud produced the fewest blossoms and fruit but fruit set was equal among all buds (65%–70%). Fruit at bud 4 were slightly smaller in diameter and weighed less than those produced at other buds. Clones with buds producing more blossoms per bud tended to produce more fruit per bud (pearson corr. coeff., r = 0.49), but a stronger correlation was found between fruit set and fruit number (r = 0.81).