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Abstract
Abundant (‘Hood’ and ‘Benton’) and poor (‘Olympus’) runnering cultivars of strawberry (Fragaria × ananassa Duch.) were grown in a milled-bark medium over an 8- or 16-fold range of slow-release ureaform N. Growth was poor or normal at low and intermediated rates of N, but inhibited at high rates. Number of leaves, crowns, and runners and subsequent inflorescence and flower production were frequently less than maximum at the highest level of N (4.8 gN/liter bark medium). Applied N had a significant effect on the number of crowns/plant, inflorescences/crown and flowers/inflorescence. In all cultivars, percent N in leaves in August, or in the entire shoot in November, showed a significant linear relationship with applied N. ‘Hood’ accumulated a higher concentration of N in both parts than ‘Olympus’ or ‘Benton’. Flower production in all cultivars was significantly correlated with the percent N in the shoot in November. Although the optimum range of applied N was similar for all cultivars, ‘Olympus’ was the most responsive to N in terms of increased leaf and flower production. When maximum values are compared, ‘Olympus’ in one year produced over 40% more leaves and 75% more flowers but at least 74% fewer runners than ‘Hood’ or ‘Benton’. ‘Benton’ was the only cultivar that at low and intermediate rates of applied N averaged less than one inflorescence/crown. Crown production by the 3 cultivars was not significantly different and high levels of applied N failed to increase the number of crowns available for flower initiation above those obtained at intermediate rates.
Abstract
‘Linn’, ‘Olympus’, and ‘Totem’ strawberry (Fragaria × ananassa Duch.) were defoliated on various dates in 1979 during mechanical harvest or by leaf mowing after hand harvest, and numbers of crown divisions, runners, and inflorescences as well as berry size, fruit rot, and yield were measured in 1980. The only difference attributable to defoliation dates was berry size in ‘Olympus’ and ‘Totem’. Defoliation by mechanical harvest did not adversely affect subsequent plant growth and yield.
Abstract
Further studies of bird damage on apples indicate that fruit dropping as a result of bird activities may be a greater economic loss than feeding damage. Since feeding wounds are caused during the fruit maturation period, the amount of dropped fruit resulting is directly related to two independent factors; first, the inherent ability of the variety to retain its fruit and second, the stage of fruit maturation when damage occurs.
Four to six-yr-old `Red Ruby' grapefruit trees on either `Volkamer' lemon (VL) or sour orange (SO) rootstocks were fertilized with 3 rates of nitrogen (N) over a 3 year period. We studied the effects of leaf N concentration on stomatal conductance (gs), net assimilation (A) of CO2 (Li-Cor portable gas exchange system), carbon isotope discrimination (δ 13C) of tree tissues, root growth, canopy development and fruit yield. Using springtime measurements of net gas exchange during the fifth year, gs, A and leaf tissue δ 13C were positively correlated with leaf N. The faster growing trees on VL had larger canopy volumes and fruit yields but lower leaf N, A and δ 13C than those on SO. Thus δ 13C was positively correlated with A but negatively related to tree size and yield. By the sixth year, δ 13C was still related to N but tree growth had apparently obscured any rootstock effects on leaf N, water use efficiency, A and δ 13C. Leaf and trunk bark tissue δ 13C did not differ but root bark had lowest δ 13C regardless of rootstock species.
Ammonium and NO3 uptake from hydroponic solutions containing 1 mm each of (NH4)2SO4 and Ca(NO3)2 were measured during development of Dendranthema ×grandiflorum (Ramat.) Kitamura `Iridon', `Sequoia', and `Sequest'. Nitrogen depletion from solutions approximated a 1 NH4: 1 NO3 ratio throughout a 90-day growth cycle (r = 0.96). Although harvest date cultivar interactions were significant for both forms of N, overall patterns of N uptake were similar among cultivars. Nitrogen removal from hydroponic solutions (milligrams per plant) was greatest from days 40 to 60; however, N removal (milligrams per gram of tissue dry weight) was greatest in the first month of development and decreased steadily until day 90. From day 40 to 60, new leaf development ceased while inflorescence buds developed to ≈1.0 cm in diameter. After this time, N uptake decreased rapidly as inflorescences expanded. Correlations between morphological changes and N demand could maximize the efficiency of applied N by matching form and application timing with plant needs.
Abstract
Nitrogen was applied to red raspberry (Rubus ideaus L. cv. Amity) in the spring (March, April, and May) at 67 and 135 kg·ha−1, and 3 pruning treatments were imposed: a) pruning of dormant floricanes at 0 cm (ground level); b) pruning of dormant floricanes at 0 cm plus cutting back primocanes to 40 cm in mid-May; and c) pruning dormant floricanes to 20 cm. Date of flowering, time interval from flowering to fruit maturity, and fruit size were unaffected. High N (135 kg·ha−1) increased yield late in the harvest season, increasing total yield by 14% (8.1 vs. 7.0 MT·ha−1). Pruning back the current season primocanes increased the number of branched canes but reduced yield per cane and did not increase total yield.
Abstract
In the 1st (1981) and 2nd (1982) fruiting years, ‘Benton’ strawberry (Fragaria x ananassa Duch.) formed 25% to 30% more crowns/plant than the advanced breeding selection OR-US 4356. ‘Benton’ had fewer trusses/crown than OR-US 4356 in 1981 (0.93 vs. 1.47) but both had 1.5 in 1982. OR-US 4356 had about 60% more fruit/truss in each season; however, ‘Benton’ had 75% greater mean berry weight than OR-US 4356, so that the 2 genotypes produced essentially the same yields/plant in each season, averaging 0.82 kg (1981) and 0.94 kg (1982). The genotypes did not differ in the total number of achenes/berry. Both showed a linear increase in berry weight with achenes/berry; yet OR-US 4356 had significantly lower berry weight than ‘Benton’ at equivalent achenes/berry. Increased berry expansion in ‘Benton’ was reflected by a reduction in number of achenes/cm2 of berry surface. The values, averaged over both seasons, were 10.6 (‘Benton’) and 14.0 (OR-US 4356). OR-US 4356 failed to produce higher yields than ‘Benton’ because of limitation in fruit expansion.
Abstract
Strawberries (Fragaria × ananassa Duch. cv. Hood) were grown at three levels of soil P and inoculated with either Glomus fasciculatus (Thaxter sensu Gerd.) Gerd. & Trappe or Gigaspora calospora (Nicol. & Gerd.) Gerd. & Trappe mycorrhizal fungus. P and N concentration in the aerial part of inoculated plants were higher than in controls; highest concentrations were found in plants inoculated with Glomus fasciculatus. Inoculation with this fungus also resulted in the greatest length of mycorrhizal roots and the highest percentage of total root length infected.
Abstract
‘Olympus’ strawberries (Fragaria × ananassa (Duch.) with and without black polyethylene mulch were compared in terms of leaflet elongation and diurnal water potential (ψ) of leaves at 2 levels of drip irrigation. Mulch increased leaflet elongation at both irrigation levels, but had no appreciable effect on soil water potential at 20 cm depth, nor on leaf ψ or leaf turgor. Leaflet elongation with black polyethylene may have been favored by the increased soil temperature throughout the upper 20 cm. At the 10-cm depth, mulched, high-moisture soil was an average of 3.0°C warmer during a diurnal cycle. Greatest warming was in late afternoon and late evening in low and high moisture soil, respectively.
Abstract
Two field plantings of strawberries [Fragaria × ananassa Duch. cv. Olympus] were grown with and without black polyethylene mulch at 3 levels of drip irrigation and differential irrigation was maintained after plant establishment for 1 month in 1977 and 2 months in 1978. During the driest portion of each year the soil water potential at 20 cm depth remained above −0.5 bars for the highest level of irrigation, and fell below −11 bars at the lowest level. Mulch conserved soil moisture at the 2 lower irrigation levels in 1977, but this effect was minor in 1978. Vegetative growth was increased by both irrigation and mulch. The number of leaves produced during the first growing season was 30% (1977) and 25% (1978) greater in the high than the low-irrigation regime. Mulching improved leaf production 27% (1977) and 14% (1978). Most of these vegetative differences between treatments were still apparent at fruit harvest the following July. During a second year of treatments on the 1977 planting, the number of leaves was further enhanced by mulch and high irrigation. At the subsequent fruit harvest, 2-year-old plants had more leaves than those 1 year old, but the leaf area per plant averaged 27% lower. Leaf and crown dry weights of either 1- or 2-year-old plants at fruit harvest were slightly greater due to irrigation and significantly higher due to mulch, whereas root dry weight was unaffected by either treatment. The amount of summer irrigation required to sustain vigorous vegetative growth in mulched plants was only one third that of unmulched strawberries.