The trend toward planting high density apple orchards continues. Closer tree spacing requires a greater degree of growth control to reduce shading and to prevent the decline in fruit quality and productivity as the planting become older. Chemical, rootstock, pruning, and management techniques will be reviewed that may control growth directly by reducing vegetative growth or indirectly through effects on increasing flower bud formation and fruit set. Pruning and management techniques will be discussed that can selectively reduce vigor in the tops of trees while allowing growth of the less vigorous lower portion of a trees to continue.
Duane W. Greene
Bruce W. Wood, Jerry A. Payne and Owen Jones
Overcrowding in young high-density pecan [Carya illinoensis (Wangenh.) C. Koch] orchards has prompted a study of tree transplanting and evaluation of survival and tree performance. Shoot growth and nut production characteristics of 13-year-old `Stuart' and `Farley' pecan trees subjected to different stubbing and pruning treatments and then transplanted with a large tree spade indicated that transplants can survive with little or no pruning if moved when dormant. Shoot regrowth was proportional to the degree of pruning, and nut production was inversely proportional to the degree of pruning.
P. Perkins-Veazie and J.K. Collins
Okra stored at 3C in 12.7-pm high-density polyethylene (HDPE) bags developed less chilling injury than fruit stored in plastic boxes. Okra held in HDPE bags at 12.5C for 8 days had more decay and reduced overall appearance than fruit held in plastic boxes. `Emerald Green' okra lost more weight in storage than the other four cultivars regardless of temperature or storage duration, while `Blondy' had the most decay. `Annie Oakley' and `Clemson Spineless' had better shelf life than the other cultivars.
W.R. Okie and D.J. Werner
Spring frosts often kill all or a portion of the flowers on peach [Prunus persica (L.) Batsch] trees in the southeastern United States. Increased flower bud density increases the likelihood of sufficient flowers surviving to produce a crop. The effect of environment on flower bud density (buds/node) was studied using two locations over 3 years. Bud density of 25 peach and nectarine varieties grown in completely randomized designs was measured in Georgia and North Carolina. Genotypic variability was greater than location or year effects. Varieties selected for high bud density at one location can be expected to have high densities at other locations with similar chilling.
G.H. Neilsen, D. Neilsen and F. Peryea
Traditionally, broadcast or foliar fertilizer applications have been used to improve or sustain the nutrition of many irrigated, deciduous fruit tree orchards in western North America. Recent developments, including adoption of low-pressure microirrigation systems and planting at higher densities [especially for apple (Malus domestica Borkh.)], have increased interest in controlled application of fertilizers directly with irrigation (fertigation). Recent fertigation research in western North America is reviewed, emphasizing results from high-density apple orchards. Fertigation and traditional broadcast application methods are examined with respect to mobility of N, P, and K in the soil and response of fruit trees to application of these nutrients.
Spur-type growth habit, among other factors, is known to reduce vigor in apple trees. High-density orchards can, therefore, be designed with more vigorous rootstocks, which do not require support systems. Trees were planted in a latin square design and trained to modified vertical axis system which, encouraged maximum limb development. Growth response of the spur McIntosh strains; `MacSpur', `Hartenhof', `Stirling', `Chick-a-dee'; and for `Empire' are compared for each of the five rootstocks MM.106, Alnarp 2, MM.111, KSC13, and KSC3. `Empire' on KSC13 grew the largest, the smallest were `Stirling', `Chick-a-dee', and `Empire' on KSC3.
Joseph A. Fiola and Robert J. Lengyen
High-density, annual, strawberry production systems (“plasti-culture”) have shown high productivity under New Jersey conditions; however, cultural practice and variety research is needed to increase profitability. The system includes raised beds, plastic mulch, trickle irrigation, and double-row 12 × 12-inch plant spacing. Polypropylene floating rowcovers were applied in December and removed in early April when flowers were visible under the cover. Treatments included comparisons of plugs and dormant crowns of the cultivars Chandler and Allstar, planted at multiple planting dates, on white or plastic mulch, in “matted-row” (single row at 18-inch spacing; peg runners through plastic) or high-density production systems. The plug plants were superior to dormant crowns. Black plastic was best all planting dates with plugs; `Allstar' performed best on black on the early planting dates, while `Chandler' preferred the white for the early planting dates. Both `Allstar' and `Chandler' had commercially profitable yield, fruit weight, and quality. “Matted-row” system on plastic is high-yielding but labor-intensive. Late-summer plugs on black plastic is best overall.
Mikal E. Saltveit and Mary E. Mangrich
The density of excised 2-cm celery (Apium graveolens L.) petiole segments was highly correlated with a subjective evaluation of pithiness. Loss of density and the appearance of pithiness was stimulated by lengthening the duration of storage, raising the storage temperatures above 0C, and excising petiole segments. Segments excised from the upper two-thirds of the petiole lost less density during storage than segments excised from the bottom third of the petiole. Segments with initial high densities lost slightly less density during storage at 5C for 5 weeks than segments that were initially less dense. The extent of pithiness development varied significantly among six cultivars held at 5C for 2 weeks. Treating whole petioles with 1 μm abscisic acid for 4 days significantly increased density loss. Exposing petiole segments to up to 100 μl·liter-1 ethylene in humidified air for up to 2 weeks at 5C did not significantly change density over air controls. The loss of density and the development of pithiness in lightly processed celery petioles could be reduced by selecting resistant cultivars, monitoring water stress during growth, using only segments excised from the upper two-thirds of the petiole, and selecting segments with initial high densities.
Yaffa L. Grossman and Theodore M. DeJong
Plant dry matter production is proportional to light interception, but fruit production does not always increase with increased light interception. Seasonal daily patterns of light interception by cling peach trees planted in four different planting density/training systems were obtained using a Decagon ceptometer. The High Density V system (1196 trees/ha) intercepted significantly more light than the KAC V and Cordon systems (918 trees/ha). The Vase system (299 trees/ha) intercepted significantly less light than the other systems. Response surfaces using a quadratic model with interactions for time of day and day of year explained 84% to 91% of the variance in the data sets for each training system. Crop yields per acre were greatest for the High Density V, followed by KAC V, Cordon, and Vase, corresponding to the light interception data. A carbon budget model, which incorporated canopy photosynthesis, respiration, and carbon partitioning based on organ growth potentials, was used to simulate seasonal patterns of carbon assimilation, crop dry weights, and individual fruit dry weights.
James P. Gilreath, Bielinski M. Santos, Myriam N. Siham, Paul Vaculin and Michael Herrington
Previous research has demonstrated stimulation of purple and yellow nutsedge (Cyperus rotundus and C. esculentus) with chloropicrin when applied at rates ranging from 100 to 150 lbs/acre (112 to 168 kg·ha–1) under low or high density polyethylene film mulch. This stimulatory effect has been exploited in research by developing a program of metam application 5 days after application of chloropicrin, thus placing metam in the soil once the tubers have begun to sprout and are most vulnerable. This project was expanded in 2004–05 to include the commercial emulsifiable concentrate formulation of 65% 1,3-dichloropropene and 35% chloropicrin (1,3-D + Pic) and virtually impermeable film mulch as well as high density polyethylene film. The test site was a commercial tomato farm in west central Florida with a heavy infestation of purple nutsedge. Chloropicrin was applied into raised beds through three gas knives, while 1,3-D + Pic and metam potassium were applied in 1 acre inch of water through 2 drip irrigation tubes spaced 10 inches apart and 5 inches from the bed center. Metam was applied 5 days after application of chloropicrin and 1,3-D + Pic. Treatments were applied under both standard high density polyethylene film (Hilex and Bromostop) VIF. Stimulation of nutsedge sprouting and emergence was about the same with either chloropicrin alone or combined with 1,3-D; however, there was some enhancement when applied under VIF. There was a slight improvement in efficacy of metam potassium when applied alone under VIF, contrary to previous results. Application of metam 5 days after application of chloropicrin or 1,3-D + Pic greatly improved nutsedge control over that observed without the subsequent application of metam and VIF improved results to some degree. Producers of drip irrigated crops in Florida can achieve acceptable to excellent nutsedge control using this sequential application technique combined with VIF; however, the addition of a second drip tube on the bed top increases expense by about $125/acre and is not compatible with crops grown with more than a single row on the bed.