Early Fruit Set Research Articles

The influence of nitrogen-fertilizer and harvest time on the productivity of Thymus vulgaris L.

The influence of nitrogen-fertilizer applied in 0, 50, 100 and 150 kg/ha dosages, as well as the time of the harvest carried out in full flowering and early fruit set stages were studied on the herb and essential oil production of garden thyme (Thymus vulgaris L.). The small plot experiment was installed in the Experimental Field of Tarbiat Modarres University near Teheran, under sandy loam soil conditions. On the basis of the results the nitrogen-fertilizer had a significant effect on the dry-matter production of the species: the herb yield, calculated on one hectare, increased from 671.88 kg up to 1021.00 kg value as a result of 150 kg nitrogen dosage. The essential oil yield proved to have a similar tendency because neither the accumulation level of essential oil, nor the ratio of thymol were effected by the nutrient supply. Analyzing the effect of harvest time changes in both dry-mass production and essential oil accumulation were observed. The highest herb yield (1238.20 kg/hectare) was obtained in early fruit set, when about.50 per cent of fruits reached their full size in the inflorescence. The accumulation level of essential oil also reached its maximum at the sane development stage, showing 0.75 per cent value, which is about two fold higher comparing to the accumulation level was measured at the time of full flowering (0.41 %).

Effect of Mulch and Shading on Bell Pepper Production in Alabama

In 1999, two studies were conducted using bell pepper (Capsicum annuum L.) Study one evaluated the effect of three different mulch systems and bare soil (BS) on day and night temperatures encountered during the early growth, flowering, and fruit set period. Mulch systems were black plastic (BP), black plastic over white plastic (BOW), and minimum tilled rye (MTR). Study two evaluated the use of a 30% shade fabric on black plastic produced bell pepper. In study one, maximum daytime temperatures during the pre-flowering phase was significantly higher for MTR, 35.9 °C, compared to, 33.3, 32.5, and 32.1 °C for BOW, BP, and BS respectively. During early fruit set and fruit development, MTR was 36.9 °C, compared to 35.6, 34.9, 34.9 °C for BWP, BS, and BP respectively. Minimum nighttime temperatures were not significantly different between treatments. Bloom numbers and fruit set were adversely affected by MRT and were significantly lower than other treatments 23 and 15 days prior to harvest. Marketable weight and number of fruit per plot were significantly lower at harvest for MRT, 2.5 kg compared to 15.7, 14.5, and 11.6 kg for BWP, BP, and BS respectively. In study two, 30% shading 15 days prior to harvest resulted in 40% increase in number, 101 and 72, and weight, 21 and 15 kg, of marketable fruit for shaded area compared to nonshaded area respectively. Numbers of culls per plot, predominately sunburned fruit in non-shaded area, were reduced 72% by shading. The potential for developing systems to improve bell pepper production in Alabama are feasible based on these studies.

654 Vegetable Transplant Biological Control Amendments

Bell pepper (Capsicum annuum) seedlings treated with various biological preparations exhibited increased root and shoot growth both in the greenhouse and during subsequent field establishment. Early fruit set and pod development showed signs of possible yield improvement by the treatments, but treatment differences were not apparent at first harvest. Data from subsequent harvests did show yield increases with some preparations. Treatment organisms appeared to activate or induce systemic resistance to bacterial spot (Xanthomonas campestris) infestation though not to the level shown by Actigard (Novartis). Crop/treatment response under soil solarization, fumigation, and compost amended conditions will be discussed.

Rate and Timing of Nitrogen Fertilization on Yield and Gross Revenue of Fresh Market Tomatoes Following a Winter Legume Cover Crop

ABSTRACT Using a winter annual legume cover crop to supply the N needs of fresh market tomatoes (Lycopersicon esculentum L.) can be beneficial to the long-term productivity of the soil and an efficient utilization of resources. Successful production is related to fruit size, quality, yield, and timing to market highs. Mineralization of N from legumes must occur at rates and timing corresponding to optimal fruit development of the crop. The objective of this study was to determine if successful vine-ripened fresh market tomato production could occur using a winter legume cover crop to the supply the N needs. A two-year study investigated the rate and timing effects of supplemental N on yield and revenue of tomatoes following an incorporated winter annual legume cover crop of Austrian winter pea (Pisium sativum subsp. arvense). Treatments consisted of 0, 67,134,202 and 246 kg N (mulched ha)−1 applied all preplant or preplant + two split N injections of 34 kg N (mulched ha)−1 each at early fruit set and 10 d...

Fruit canopy position and panicle bagging affects yield and quality of `Tai So' lychee

To determine the potential for fruit bagging to improve the quality of lychee, panicles on the northeast (NE), southeast (SE), southwest (SW) and northwest (NW), and at the top and bottom of the canopy of 12-year-old `Tai So' lychee trees, were enclosed in paper bags at early fruit set, at 1/2–3/4 fruit fill, and just before fruit colouring (corresponding to 80, 42 and 28 days before harvest). At commercial maturity, panicles from the NE and NW aspects and from the upper canopy had the greater number and mass of fruit per panicle, than panicles from the other parts of the canopy. Bagging had no significant ( P<0.05) effect on panicle yield. Fruit from the NW aspect were of lower visual quality, due mainly to light and dark brown blemishes on the skin, rather than the colour of the red portion of the skin. Lower canopy and NE fruit were less red (higher hue angle; h°), but there was little effect of canopy height on visual quality. Bagging increased the percentage of fruit in first class, mainly because of increased visual quality of fruit from the NW and SE aspects. The percentage of second class fruit was not affected by bagging, but the percentage rejects was reduced. Unbagged fruit had a lower Chroma (C *) and a higher h°, especially in fruit from the NE. Fruit from the NE and NW aspects and from the lower canopy, had lower brix/acid ratios. Thus, bagging has the potential to improve fruit quality and red colour with no negative impact on yield.

691 PB 265 DRIP IRRIGATION AND FERTIGATION MANAGEMENT CAN MINIMIZE NITRATE LEACHING LOSSES

Trials were conducted under California field conditions examining the impact of drip irrigation and nitrogen fertigation regime on in-season NO3-N leaching losses. Six field studies were conducted, 4 on tomato and 2 on pepper. Seasonal fertigation ranged from 0-440 kg N/ha; irrigation was applied 3X per week, with leaching fractions of 10-25% of applied water. NO3-N leaching losses were estimated both by suction lysimetry and the use of buried anion resin traps. A similar pattern was seen in all trials. From transplant establishment until early fruit set soil solution at 0.8 m had relatively high NO3-N concentration (&gt;30 mg/liter), which declined as the season progressed; in the month before harvest soil solution NO3-N at 0.8 m was consistently below 10 mg/liter (tomato) and 15 mg/liter (pepper) in appropriately fertilized plots. Seasonal NO3-N leaching estimates were generally below 25 kg/ha (tomato) and 35 kg/ha (pepper), with only modest differences among fertigation regimes. These results suggest that well managed drip irrigation can minimize in-season NO3-N leaching.

Effects of hydroponic solution composition, electrical conductivity and plant spacing on yield and quality of strawberries

The influence of nutrient solution adjustment and replacement (management), its electrical conductivity (EC) and plant spacing on yield and quality of strawbeny fruit (var. Torrey) produced in a recirculating hydroponic system was studied at Gosford, New South Wales. Four ways of managing the nutrient solution were examined: (i) pH and EC adjusted daily and the solution replaced every 8 weeks (current grower practice); (ii) as above except that a topping up solution with lower potassium to nitrogen (K: N) ratio was used for EC adjustment; (iii) no daily adjustment of EC or pH and one-third of solution replaced every 2 weeks; and (iv) no daily adjustment of solution volume, EC or pH and full replacement after 8 weeks. Compared with grower practice, these alternative solution management strategies provided no advantage in yield, fruit number, or in the �Brix, citric acid, sweetness or flavour of fruit. Use of a topping up solution supplemented with ammonium nitrate (NH4NO3) and calcium nitrate [Ca(NO3)2] to reduce the K : N ratio from 1.7:1.0 to 1.4:1.0 had no effect (P&gt;0.05) on yield but significantly increased (P&lt;0.05) berry weight and improved fruit aroma. Regardless of which method of nutrient solution adjustment and replacement was used, the chemical composition of the recirculating solution changed markedly over 53 days. The method of nutrient solution management significantly (P&lt;0.05) affected leaf phosphorus (P), calcium (Ca), magnesium (Mg), manganese (Mn), and zinc (Zn) but only Mg fell to a suboptimal level for growth of strawberries. Reducing the EC of the nutrient solution from 3 to 2 dS/m at early fruit set gave heavier (P&lt;0.05) berries compared with constant EC of 2 dS/m. Increasing the EC from 2 to 3 or reducing it from 3 to 2 at early fruit set resulted in sweeter (P&lt;0.05) berries and reducing the EC from 4 to 2 improved fruit aroma. Yield declined (P&lt;0.05) when EC was increased from 2 to 4 dS/m. Solution EC bad significant effects (P&lt;0.05) on leaf P, Mg, Mn and Zn. An increase in planting density from 5.35 to 9.35 plants/m2 lowered (P&lt;0.05) marketable yield per plant and fruit acidity but gave 41% higher (P&lt;0.05) yield on an area basis.

Modelling of the flows and partitioning of carbon and nitrogen in the holoparasiteCuscuta reflexaRoxb. and its hostLupinus albusL.

A recently developed empirically based modelling technique was used to quantify uptake, flow and utilization of C and N in Lupinus albus L., uninfected and parasitized by Cuscuta reflexa Roxb. plants over a 12 d period during flowering and early fruit setting of the host. The modelling combined data on molar C:N ratios in host phloem and pressure-induced xylem sap, net increments of C and N in host and parasite plant parts and respiratory losses of C. The modelling of the solute transfer between host and Cuscuta was achieved by assuming non-specific intake from the xylem. The models predicted that Cuscuta derived 99.5% of its carbon and 93.6% of its nitrogen demand from the host phloem

Spunbonded Polypropylene Fabric Covers Can Enhance Cranberry Establishment and Production

Low levels of available carbohydrates early in the growing season are important in limiting fruit set in cranberries (Birrenkott et al., 1991). Stang (1991) and Stang et al. (1991) investigated the use of fabric covers to enhance early season carbohydrate levels and fruit set in cranberries in Wisconsin. They reported that covers increased plant chlorophyll content, photosynthesis, and upright growth in new bogs. There was an inconsistent or negative effect, however, on fruit set and yield in bearing bogs. Cranberries grown in areas with a cool maritime climate and an extended flowering period might benefit more from placing rowcovers early than would those grown in the continental climate of Wisconsin. Fabric covers also may be beneficial in cooler climates to hasten vining-over of new bogs or to increase production of established bogs. New planting. To determine the effect of fabric covers on new bogs, ‘Stevens’ cranberry vines were planted 15 Apr. 1990 in sandy loam soil at Long Beach, Wash. Spunbonded polypropylene fabric (21 g·m-2) (KimberlyFarms,Roswell,Ga.)covered young vines from 6 June to 9 Sept. Plot size was 15× 15 m. Covers were held in place with metal pipes along the perimeters. There were four replications each of covered and noncovered plots in a randomized complete block design. All plots received identical cultural practices. Plots were rated for the amount of ground covered by vine growth (vining-over) on 31 Aug. 1990 and 24.Aug. 1991, and for incidence of red leaf spot (Exobasidium rostrojii Nannf.) on 10ct. 1990. In Dec. 1990, a 15-m transect was laid within each plot along a line where the vines had been disked in at planting. At six randomly selected locations along that line, a 0.1 × 0.33-m area of vines was harvested and fresh weight recorded. Covers improved vining-over of a new planting the first

Manipulation of shoot growth patterns in relation to early fruit set in ‘Hass’ avocado ( Persea americana Mill.)

Shoot tipping and pruning, rootstocks and plant growth regulator applications were evaluated for their potential to change canopy structure and improve productivity of ‘Hass’ avocado. Tipping and pruning were successful in limiting the length of the primary shoot axis and increasing axillary branching, without influencing total fruit set. Trees on the rootstock ‘Velvick’ had greater vigour with a higher ratio of sylleptic to proleptic shoots than trees on ‘Hass’ rootstock. The growth inhibitor Cultar (paclobutrazol) reduced shoot length and leaf size, but had no effect on the number of shoots or on fruit set. The auxin inhibitor TIBA (2,3,5-triiodobenzoic acid) stimulated proleptic axillary shoot growth without effect on fruit set. Cytolin (6-benzyladenine and gibberellins 4+7) increased sylleptic axillary shoot growth and subsequent fruit set, but the timing of application was critical. Manipulation of sylleptic shoot growth may provide the key to improving tree form and productivity in avocado.

Simulation of salmonberry and thimbleberry population establishment and growth

A salmonberry (Rubusspectabilis Pursh) and thimbleberry (Rubusparviflorus Nutt.) population simulation model was developed and compared with field observations for verification and validation. The species-specific influence of different phenological stages (early spring bud break, early summer fruit set, and fall senescence), different environments (at different sites), and intraspecific density on demographic processes was incorporated into the model. The model predicts the number of individuals in different life-history stages at three phenological stages during a growing season. Simulations were most accurate when compared with low genet density planted populations. Salmonberry populations on a moist site were most accurately simulated. Thimbleberry simulation accuracy was reduced by poor prediction of sprout densities. Salmonberry and thimbleberry population response to an application of glyphosate was simulated and compared with observed canopy cover for 3 years following application. The simulated response was accurate for the 1st year following application, but did not account for continued canopy cover in the observed populations. Salmonberry canopy cover and mean ramet height in response to manual cutting at three phenological stages was also simulated. The model simulations indicated that the most prolonged reduction in salmonberry cover followed cutting at the reproductive stage of growth.

`Super Chief' Tomato Hybrid

‘Super Chief’ is the F, hybrid resulting from the cross SD 82-106 × SD 85-048-l. Both parents were developed in the South Dakota fresh-market tomato (Lycopersicon esculentum Mill.) breeding program (Fig. 1). The purpose of this breeding project is to develop tomato hybrids that are early, have acceptable fruit size (2120 g/fruit), and set enough fruit in fluctuating temperatures. ‘Super Chief’ is early and has larger fruit and a more consistent and heavy fruit set than varieties currently recommended in South Dakota. Other hybrids developed in this program are ‘Centennial’, ‘Bonanza’, ‘Golden Delight’, ‘Rushmore’, and ‘Pink Pearl’. The first cross was made in Fall 1982 in the greenhouse and tested during the past 10 years. Parent line SD 82-106 is the result of several matings designed to combine resistance to verticillium wilt [Verticillum albo-atrum (Sacc.) Snyder&Hansen] race 1 and fusarium wilt (Fusarium oxysporum f. lycopersici Reinke & Berthold) race 1 and to incorporate the ability to set fruit with this region’s fluctuating temperatures. Line SD 85-048-l is a result of several matings and selection for large fruit, early fruit set, resistance to verticillium and fusarium wilt, and other desirable horticultural characteristics. ‘Super Chief’ was evaluated as SD 87-13.

Watermelon Phosphorus Requirements in Soils with Low Mehlich-I-extractable Phosphorus

Watermelon [Citrullus lanatus (Thunb.) Matsum. &amp; Nakai] was grown at two sites differing slightly in Mehlich-I (double-acid) -extractable P (6 and 10 mg·kg-l soil). Early and total yields responded positively to P rate; however, maximum yields were obtained with small amounts of P fertilizer. The linear-plateau critical P fertilizer rates were 26 and 27 kg·ha-1 at sites 1 and 2, respectively. These critical rates were lower than those currently used for recommending P fertilizer on soils that have very low P. Phosphorus concentrations of most-recently matured leaves at early fruit set were 2.5 and 2.8 g·kg-1 at sites 1 and 2, respectively, with 0 P, and 4.4 and 4.8 g·kg-1 with the 25-kg P/ha treatment.

LODGING IN DIRECT SEEDED PEPPERS

One of the problems associated with machine harvesting of spice peppers (Capsicum annuum L.) is plant lodging. Factorial combinations of four bedding treatments and two N rates were compared for effects on lodging and fruit yield of Chile at Fort Cobb and Bixby, Okla.. and of paprika at Bixby, Okla. Bedding treatments were: 1) no-bed; 2) no-bed with 5 cm of soil hilled to the bases of plants; 3) bedded preplant but bed not maintained throughout the growing season; and 4) bedded preplant and bed maintained throughout the growing season. All plots received preplant N at a low rate (45 kg ha-1). Half the plots also received a topdressing of 45 kg ha“ of N at early fruit set. No significant differences were found among the different bedding treatments for lodging. Bedding treatments one and three led to higher Chile yields at Bixby than treatments two and four. Bedding treatments one and two led to higher paprika yields than treatments three and four. Chiles showed an increase in plant height and width with the higher N rate at both locations. The higher N rate also increased plant dry matter and fruit yield in all three studies. Paprika uprooting force was greater in treatments two and four compared to treatments one and three.

Honey Bee (Hymenoptera: Apidae) Visits and Pollen Source Effects on Fruiting of ‘Gulfcoast’ Southern Highbush Blueberry

Bee visitation levels and pollen sources were varied in an effort to optimize fruit production (especially early ripening, fruit set, and berry weight) of southern highbush blueberry (low chill hybrids of Vaccinium corymbosum L.). Fruiting plants (‘Gulfcoast’) were enclosed in nylon-mesh cages with colonies of honey bees, Apis mellifera L., and pollinizer plants affording either intravarietal self-pollination, intervarietal crossing, or interspecific crossing with rabbiteye blueberries, Vaccinium ashei Reade. Newly opened blossoms were allowed 0, 1, 5, 10, or unlimited bee visits before being closed with a fine mesh bag. Significant improvements in fruiting characters were achieved between one and five visits and also usually between five and unlimited visits. Fruit set more than tripled between the fewest- and greatest-visit levels; set peaked near 70%. The pollination-toharvest interval, a chief determinant of blueberry prices in the early season, was shortened by 5 d to 53 ± 0.5 (SE) d. Berry weight increased 28% from the 0- and I-visit groups to 1.77 ± 0.05 g per berry with unlimited visits. Seed numbers increased 2.2-fold to 40 ± 1 seeds per berry. Sugar concentration of juice ranged from 11.0 to 12.9% and was lower at greater levels of bee visitation. Pollen source did not have a significant effect on any fruiting character measured in ‘Gulfcoast’.

Influence of shoot age on floral development and early fruit set in avocado(Persea americanaMill.) cv. Hass

Floral bud development, early fruit set, bud size, leaf nitrogen and shoot starch content were recorded in spring, summer and autumn shoots of ‘Hass’ avocado (Persea americana Mill.). Floral initiation occurred in late autumn, but only in buds on terminal shoots (the last-formed shoot module on a terminal or axillary growth axis). In branching systems with three growth flushes, more flowers were produced and more fruit set on autumn and summer, than on spring flush terminal shoots. Floral development and leaf nitrogen accumulation occurred later in autumn than in summer shoots, but leaf numbers, dry and fresh weights, starch content of wood, mean floral status at anthesis and anthesis date were similar. The results suggest that nitrogen and starch were present in excess during floral development, and that shoot age did not influence the ability of a shoot to flower and set fruit, provided the shoot had sufficient vigour to produce new shoot growth in spring.

UTILIZATION OF SOIL-APPLIED AUXINS FOR SYNCHRONIZATION OF FRUIT SET AND YIELD INCREASE IN CITRULLUS LANATUS.

Exogenous application of auxins to plants has been reported to increase flowering, fruit set and decrease fruit abcission. This laboratory and field study determined that two auxins, identified by HPLC analysis with a long soil residence time and a high conversion to indole-3-acetic acid, synchronized and increased harvest of melons. The two watermelon varieties, `Tiffany' (seedless) and `Picnic' (seed) were treated with auxin and tryptophan (TRP) concentrations ranging from 10-4 to 10-10 M applied to the root ball one week before transplanting to a Buren soil. Optimum application levels (10-6 to 10-9 M) resulted in 86, 92 and 86% of the total harvested Tiffany melons mature at one date for the auxins and TRP, respectively, compared to &lt;70% for the control plants. Optimum application rates significantly increased harvested weight 4.0 and 5.3 kg (Tiffany) and 10.0 to 10.5 kg (Picnic) plant-1. Soil-application of auxins and TRP significantly increased the number of harvested Tiffany melons, increased both weight and harvested number of Picnic melons and increased the uniformity of the harvested melons in both varieties when compared with control plants. Measurements of early growth, branching and early fruit set were not significantly correlated with harvest weight or number of harvested melons but auxin and TRP application stimulated flowering in both melons by 7-10 days.

Influence of planting date and row covers on yields and crop values for bell peppers in Saskatchewan

In 1989 and 1990, bell peppers transplanted into the field in mid-May, late May or early June were grown with a black plastic soil mulch and no cover (NC) or under tunnels of perforated clear polyethylene (PT) or spunbonded polyester (ST). The ST treatment provided several degrees of frost protection, whereas the PT treatment appeared to increase the crop’s susceptibility to frost damage. Early planting had little effect on total fruit yields but did accelerate the harvest. In both years, the ST accelerated crop maturity and increased total fruit yields relative to the noncovered treatment. At times the PT improved crop development and increased fruit yields, but in many cases it reduced fruit yields relative to the noncovered treatment. By promoting early fruit set and development, early planting under the spunbonded row covers significantly enhanced the value of the crop, as early peppers command a premium price in Saskatchewan. Cumulative crop values for the PT treatments were generally similar to or poorer than those for the noncovered control.Key words: Bell pepper, Capsicum annuum, planting date, row covers, frost

An Agrometeorological Model for Assessing the Effect of Heat Stress During the Flowering and Early Fruit Set on Avocado Yields

Abstract An agrometeorological model was developed for assessing the effect of heat stress during flowering and early fruit set on avocado (Persea americana Mill) yields. This model accounted for heat stress only and was considered to occur when the daily maximum temperature was ≥33°C. In addition to the daily maximum temperature, the model considered the duration of such temperatures in days, as well as the timing of the occurrences of such temperatures in relation to the flowering and early fruit set of ‘Fuerte’ avocado. The specifications of the climatic data inputs are based on experimental results in the temperature range of 33° to 43°C extrapolated linearly. A series of weighting factors were used for the duration of heat spells in days. In the temperature range of 33° to 35° the weighting was n − 1; for the 36° to 38° range, 1.4n; and for the 39° to 43°C range, 2.0n. Weighting factors for the timing of the occurrence of heat spells follow closely the near-normal percentage distribution curve of open flowers. At bud burst in March, the weighting is 0.4, increasing to 1.3 at early fruit set by mid-May and decreasing rapidly to 0.3 by the end of June. The functional relationship between the model heat stress output and the yield of avocado for an irrigated, high-yielding plantation shows fairly good correlation, r2 = 0.42 to 0.51, depending on the statistical method used. The agreement between the heat stress index and the yield of avocados is closely related only during those years when the plantation is subject to heat stress indexes greater than 10. Testing the model on independent data commenced in 1985 and includes a yield memory term.

Effects of hydrogen fluoride on incorporation and transport of photoassimilates in soybean

The effect of hydrogen fluoride (HF) on the translocation and partitioning of 14C between transport and nontransport photoassimilates from source leaves to sink regions was studied. Soybean plants (Glycine max (L.) Merr. cv ‘Hodgson 78’) were fumigated continuously with HF at 0, 1, and 5 μF-m−3 for 8 to 10 d at three stages of development (vegetative, flowering and early fruit set, and pod filling). The second fully expanded trifoliolate leaf of experimental plants was exposed to 14CO2. In plants exposed to HF, there was an increased retention of 14C-labelled assimilates in foliage (source tissue), accompanied by a reduced export of these compounds to other plant parts (path and sink tissues). There was also a greater incorporation of 14C into nontransport ethanolinsoluble assimilates at the expense of the ethanol-soluble transport assimilates in source leaves. When compared with control plants, exposure to HF also increased the proportion of 14C incorporated into sugars in source leaves accompanied by a decrease in 14C-sugars in sink tissues. Results suggest that the retention of sugars in source leaves and the reduction in allocation to sink tissue may be a result of the inhibition of the process involved in the export of sugars from the leaf (i.e., phloem loading). An inhibition of phloem loading may result in an accumulation of sugars in the mesophyll cells, which may exhibit feedback inhibition on starch degradation and/or stimulation of starch synthesis.