`Hamlin' and `Valencia' oranges [Citrus sinensis (L.) Osb.], `Murcott' tangor (C. reticulata Blanco × C. sinensis), and `Redblush' grapefruit (C. paradisi Macf.) on 15 rootstock and own-rooted cuttings were planted at a 1.5 × 3.3-m spacing providing a density of 2020 trees/ha. Growth rate, productivity, and fruit quality varied among the scion and stock combinations. Combinations of moderate vigor and precocious fruiting performed better than very vigorous or dwarfing materials. Several freezes slowed canopy development and delayed production. Most trees had filled their allocated canopy space 7 years after planting. At that age, the orange trees yielded 23 to 75 t·ha-1. Scion and stock combinations with desirable vigor and fruiting characteristics were satisfactory in this high-density planting. However, there appears to be little advantage of high tree density under Florida conditions, and moderate densities of fewer than 1000 trees/ha may be preferable.
T.A. Wheaton, W.S. Castle, J.D. Whitney and D.P.H. Tucker
J.G. Williamson and D.C. Coston
Several planting treatments modified vegetative and reproductive growth of young, own-rooted peach (Prums persica) trees evaluated at two levels of irrigation in a high-density orchard (5000 trees/ha). Trees planted in auger holes, narrow herbicide strips, and in fabric-lined trenches, but not those from raised beds, were smaller than control trees set in holes dug with a shovel. After two growing seasons, trees planted in the fabric-lined trenches were smaller and had more flowers per node and greater flower bud densities than trees in other planting treatments. Yield efficiency was greatest for this treatment, although fruit size was small throughout the orchard. Irrigation rates did not affect fruit yield or size. The effects of irrigation rate on vegetative growth were small compared to differences among planting treatments.
Stephen M. Southwick, W. Krueger, J.T. Yeager and J. Osgood
French prunes (Prunus domestica L.) on myrobalan seedling rootstock were planted in 1981 in an east-west direction with 4.9 m between rows and 2.7 m between trees on a poorly drained Class II soil in Glenn County, CA. A randomized complete block design was used with 8 trees per plot. Trees were pruned by hand to an open-center tree form or pruned by machine to a pyramid form in the dormant or summer season resulting in 6 pruning treatments. This high density system has led to high yields of good quality fruit (9.18 dry tons/acre in 1989, sized at 78 fruit per pound). Hand pruning led to higher yields, larger fruit, lower drying ratios and a greater dollar return per acre than any of the machine pruned trees. Dormant machine pruning led to larger fruit produced than those trees pruned in the summer by machine. Mechanical pruning may be possible for short time periods, but continued practice led to smaller fruit with lower yields than hand pruning. Certain locations within the tree canopy had smaller fruit size and it is within those lower locations where fruit size needs to be improved. These and additional experimental results obtained from 1987 through 1989 growing seasons will be presented.
David Bryla and Bernadine Strik
Many growers in the Pacific Northwest are planting blueberry fields at higher densities to improve yields and increase the number of berries harvested per acre in the first few years after planting. The objective of this study was to determine the effect of high-density planting on blueberry water requirements. Although close spacing reduces individual plant size, we expected that plants spaced closer together would require more irrigation per unit land area than those spaced further apart due to increased canopy coverage within rows. The study utilized a 5-year-old planting of highbush blueberry, consisting of three cultivars, `Duke', `Bluecrop', and `Elliott', planted at 0.5- and 1.2-m in-row spacings. Plant water use was calculated from changes in soil water content measured using TDR probes for shallow depths and a neutron probe and access tubes for deeper depths. Stem water potentials were also measured periodically using a pressure chamber to determine how well irrigation was meeting crop water demands throughout the season. Surprisingly, plants spaced 0.5 m apart required only slightly more water than those spaced 1.2 m apart. They did, however, require more frequent irrigations due to their smaller root systems, especially during fruit filling. Water use by each cultivar increased during fruit filling and then rapidly decreased after harvest. `Duke' required the most water among cultivars, using 5–10 mm/day from mid-May to mid-August, while `Elliott' required the least, using 3–5 mm/day.
J.G. Williamson, D.C. Coston and J.A. Cornell
Planting treatments were evaluated for their influence on shoot development and root distribution of own-rooted `Redhaven' peach [Prunus persica (L.) Batsch] trees planted to high density (5000 trees/ha). Planting in fabric-lined trenches (FLT) or narrow herbicide strips (NHS) reduced the diameter and length of primary shoots, the number and combined length of second-order shoots, and the total length of shoots. Flower density, the number of flowers per node, and the percentage of nodes containing one or more flowers were increased for FLT trees but not for NHS trees when compared with controls. The length of primary shoots increased quadratically for all treatments with increasing limb cross-sectional area (LCA). The total length of shoots increased more with increasing LCA for controls than for FLT trees. The number of flowers per shoot increased linearly for all treatments with increasing LCA values. Root concentration decreased with increasing soil depth and distance from tree rows for all treatments. Reduced widths of weed-free herbicide strips had little effect on root distribution. Roots of FLT trees were reduced in number and restricted vertically and laterally when compared with other planting treatments. The FLT treatment modified shoot development by reducing the length of total shoots and length of primary shoots across LCA values measured when compared with NHS and control-treatments.
D. Neilsen and G.H. Neilsen
In irrigated apple orchard systems, the magnitude and timing of plant demand for nitrogen (N) and retention of N in the root zone to allow root interception are important factors for efficient management of N fertilizer. Results from five experiments in high-density plantings of apple (Malus domestica) on dwarfing (`Malling 9') rootstocks are reported. All experimental plots received daily drip irrigation and N applied through the irrigation system (fertigation) with different regimes according to experimental design. Labelled fertilizer applications, whole tree excavation and partitioning and removal of N in fruit and senescent leaves were used to assess tree N demand. Nitrogen requirements ranged from 8 to 40 lb/acre (8.8 to 44 kg·ha-1) over the first 6 years after planting and N use efficiency was often low (<30%), likely because supply exceeded demand. Annual growth is supported by N remobilized from storage and taken up by roots. Root uptake of labelled fertilizer was negligible during early spring and the commencement of rapid uptake was associated with the end of remobilization and the start of shoot growth, rendering prebloom fertilizer applications ineffective. Thus timing of N supply to periods of high demand is crucial for improving efficiency. Comparisons were made to determine the effects on N leaching and tree N utilization of irrigation scheduled to meet evaporative demand and irrigation applied at a fixed rate. Water losses beneath the root zone were greater for fixed rate than scheduled irrigation during the coolest months (May, June and September) of irrigation application. Nitrogen leaching followed a similar pattern during times of N fertigation (May and June). Greater N use efficiency was also measured for trees when irrigation was scheduled to meet evaporative demand rather than applied at a fixed rate. The most N efficient management system was for trees receiving a low [50 ppm (mg·L-1)] fertigated N supply, at 0 to 4 or 4 to 8 weeks following bloom with scheduled irrigation.
Richard E.C. Layne, Chin S. Tan, David M. Hunter and Robert A. Cline
Seven treatment combinations of irrigation and fertilizer were compared in a high-density (606 trees/ha) management system for peach [Prunus persica (L.) Batsch cv. Harrow Beauty/Bailey] on Fox sand in southwestern Ontario. Each treatment combination had an irrigation component (N = nonirrigated, D = drip irrigated, or M = microsprinkler irrigated) and a fertilizer placement component (B = banded fertilizer, L = low fertigation, or H = high fertigation). NB and DB are commonly used systems in Ontario, while the other five treatment combinations were experimental. Total soil water in the top 110 cm of soil was lowest under NB but was never at the permanent wilting point. Trunk cross-sectional area was largest under DH and DB, smallest under ML and NB, and intermediate for the other three treatment combinations. No symptoms of N or K deficiency or toxicity were noted for any of the fertilizer treatments. Leaf analyses in July and September indicated that most major and minor elements were in the adequate to slightly excess range. However, there were no significant treatment effects on leaf nutrient concentrations in July or September when averaged over the five years, except for Mg in July. There were large and significant year effects on leaf nutrient concentrations but no significant treatment × year interactions. During the first four cropping years, there were no significant treatment effects, averaged over years, for total yield, marketable yield, or cumulative yield efficiency; however, there were large year effects but no treatment × year interactions for these factors. There was no detectable yield advantage for D vs. M irrigation. B application of N and K promoted no higher yields than fertigation equivalent to the B rate or 50% of this rate. Fertigation of N and K during the first 4 years of this experiment did not provide a detectable yield advantage to warrant the added cost and labor associated with this system compared with the B applications of N and K.
G.H. Neilsen, E.J. Hogue, T. Forge and D. Neilsen
`Spartan' apple (Malus×domestica Borkh.) trees on M.9 (T337) rootstock were planted in April 1994 at 1.25 m × 3.5 m spacing. Seven soil management treatments were applied within a 2-m-wide strip centered on the tree row and arranged in a randomized complete-block experimental design. Treatments included a weed-free strip (check) maintained with four annual applications of glyphosate; surface application of 45 t·ha-1 of Greater Vancouver Regional District (GVRD) biosolids applied in 1994 and again in 1997; mulches of shredded office paper; alfalfa (Medicago sativa L.) hay; black woven polypropylene; and shredded paper applied over 45 t·ha-1 GVRD-and Kelowna-biosolids applied in 1994 and 1997. All experimental trees were fertigated with phosphorus (P) in the first year and with nitrogen (N) annually. Cumulative yield for the first five harvests was higher for trees subjected to any soil management treatment relative to check trees. Maximum cumulative yield, exceeding check trees by 80%, was measured for trees grown with a shredded paper mulch with or without biosolids application. Trees from the three shredded paper treatments were the only ones significantly larger than check trees after six growing seasons. No increases in leaf nutrient concentration were consistently as sociated with improved tree performance. Notable effects included increased leaf P concentration associated with biosolids application, increased leaf K concentration after alfalfa mulch application and temporary increases in leaf Zn and Cu concentration associated with application of biosolids high in Zn and Cu. Use of both mulches and biosolids amendments benefits growth of trees in high density plantings despite daily drip irrigation and annual fertigation.
Richard E.C. Layne, Chin S. Tan, David M. Hunter and Robert A. Cline
Seven high-density (606 trees/ha) management systems for peach [Prunus persica (L.) Batsch cv. Harrow Beauty/Bailey] were compared on Fox sand in southwestern Ontario. Each system had an irrigation component (N = none D = drip, M = microsprinkler) and a fertilizer placement component (B = banded, L= low-rate fertigation, H = high rate fertigation). NB (nonirrigated, banded fertilizer) and DB (drip-irrigated) are commonly used systems in Ontario, while the other five treatment combinations were experimental. Trunk cross-sectional area (TCA) was generally greatest for DH and DB systems, smallest for ML and NB systems, and intermediate for the other three. No symptoms of N or K deficiency or excess were noted for any of the fertilizer treatments. The seven management systems each had similar cumulative yield efficiencies for the first 4 cropping years However, total marketable yields for the 4 years were highest for MB (58.7 t·ha–1), followed in descending order by DB (56.8 t·ha–1), DH (56.6 t·ha–1), MH (53.9 t·ha–1), DL (50.6 t·ha–1), ML (49.8 t·ha–1), and NB (47.5 t·ha–1). Each of the irrigated treatments outyielded the nonirrigated check (NB) and ranged from 4.8% to 23.6%. Only one of the irrigated treatments (MB) outyielded the irrigated check (DB), and by only 3.3%. There was no clear advantage for either the drip or microsprinkler system of irrigation. Banded application of N and K appeared to promote higher yields than by fertigation equivalent to the banded rate, while yields at the low rate of fertigation were lower than for either the high rate of fertigation or the banded application. It appeared that banded fertilizer combined with either microsprinkler (MB) or drip irrigation DB provided the most-effective of the management systems in the first 4 cropping years.
Haijun Zhu and Eric T. Stafne
Due to the strong vegetative nature of relatively young pecan trees and the absence of dwarfing rootstocks or cultivars, controlling tree size is a major problem in high-density pecan orchards. Paclobutrazol, an effective inhibitor of gibberellin