Optimal Nutrient Concentration Ranges of ‘Hass’ Avocado Cauliflower Stage Inflorescences—Potential Diagnostic Tool to Optimize Tree Nutrient Status and Increase Yield

Optimizing ‘Hass’ avocado (Persea americana Mill.) tree nutrient status is essential for maximizing productivity. Leaf nutrient analysis is used to guide avocado fertilization to maintain tree nutrition. The goal of this research was to identify a ‘Hass’ avocado tissue with nutrient concentrations predictive of yields greater than 40 kg of fruit per tree. This threshold was specified to assist the California avocado industry to increase yields to ≈11,200 kg·ha−1. Nutrient concentrations of cauliflower stage inflorescences (CSI) collected in March proved better predictors of yield than inflorescences collected at full bloom (FBI) in April, fruit pedicels (FP) collected at five different stages of avocado tree phenology from the end of fruit set in June through April the following spring when mature fruit enter a second period of exponential growth, or 6-month-old spring flush leaves (LF) from nonbearing vegetative shoots collected in September (California avocado industry standard). For CSI tissue, concentrations of seven nutrients, nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), sulfur (S), zinc (Zn), and copper (Cu) were predictive of trees producing greater than 40 kg of fruit annually. Conditional quantile sampling and frequency analysis were used to identify optimum nutrient concentration ranges (ONCR) for each nutrient. Optimum ratios between nutrient concentrations and yields greater than 40 kg per tree were also derived. The high nutrient concentrations characterizing CSI tissue suggest current fertilization practices (timing or amounts) might be causing nutrient imbalances at this stage of avocado tree phenology that are limiting productivity, a possibility that warrants further investigation. Because CSI samples can be collected 4–6 weeks before full bloom, nutritional problems can be addressed before they affect flower retention and fruit set to increase current crop yield, fruit size, and quality. Thus, CSI nutrient analysis warrants further research as a potential supplemental or alternative tool for diagnosing ‘Hass’ avocado tree nutrient status and increasing yield.

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Properly Timed Soil-applied Nitrogen Fertilizer Increases Yield and Fruit Size of `Hass' Avocado

Journal of the American Society for Horticultural Science ◽

10.21273/jashs.126.5.555 ◽

2001 ◽

Vol 126 (5) ◽

pp. 555-559 ◽

Cited By ~ 9

Author(s):

Carol J. Lovatt

Keyword(s):

Fruit Size ◽

Persea Americana ◽

Double Dose ◽

Cumulative Yield ◽

Phenological Stages ◽

N Application ◽

Large Size ◽

Tree Phenology ◽

Hass Avocado ◽

Applied Nitrogen

To protect groundwater from potential nitrate pollution, `Hass' avocado (Persea americana Mill.) growers in California divide the total annual soil-applied nitrogen (N) fertilizer (N at 56 to 168 kg·ha-1) into small applications made during the period from late January to early November. However, no research had been conducted to test the efficacy of this fertilization practice, and there was concern that the amount of N in the individual applications may be too little to meet the demand of the tree at some stages of its phenology. The research presented herein addressed the question of whether yield of `Hass' avocado could be increased by doubling the amount of N currently applied during specific stages of tree phenology. The control in this experiment was the practice of annually applying N as NH4NO3 at 168 kg·ha-1 (168 trees/ha) in six small doses of N at 28 kg·ha-1 in January, February, April, June, July, and November. From these six application times, five were selected on the basis of tree phenology and additional N as NH4NO3 at 28 kg·ha-1 was applied at each time for total annual N of 196 kg·ha-1. Two phenological stages were identified for which N application at 56 kg·ha-1 in a single application (double dose of N) significantly increased the 4-year cumulative yield (kilograms fruit per tree) 30% and 39%, respectively, compared to control trees (P ≤ 0.01). In each case, more than 70% of the net increase in yield was commercially valuable large size fruit (178 to 325 g/fruit). The two phenological stages were when shoot apical buds have four or more secondary axis inflorescence meristems present (mid-November); and during anthesis to early fruit set and initiation of the vegetative shoot flush at the apex of indeterminate floral shoots (about mid-April). When the double dose of N was applied at either of these two stages, the kilograms and number of large size fruit averaged across the 4 years of the study was significantly greater than the control trees (P ≤ 0.01). Averaged across the 4 years of the study, only the November treatment increased yield compared to the control trees (P ≤ 0.05). Application of the double dose of N at flower initiation (January), during early-stage gynoecium development (February), or during June drop had no significant effect on average or cumulative yield or fruit size compared to control trees. Application of the double dose of N in April significantly reduced the severity of alternate bearing (P ≤ 0.05). Yield was not significantly correlated with leaf N concentration. Time and rate of N application are factors that can be optimized to increase yield, fruit size, and annual cropping of `Hass' avocado. When the amounts of N applied were equal (196 kg·ha-1), time of application was the more important factor.

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Nitrogen Fertilization Strategies for the ‘Hass’ Avocado that Increase Total Yield Without Reducing Fruit Size

HortTechnology ◽

10.21273/horttech.26.4.426 ◽

2016 ◽

Vol 26 (4) ◽

pp. 426-435 ◽

Cited By ~ 3

Author(s):

Jaime E. Salvo ◽

Carol J. Lovatt

Keyword(s):

Shoot Growth ◽

Important Determinant ◽

Total Yield ◽

Fruit Size ◽

Fertilizer Application ◽

Persea Americana ◽

Phenological Stages ◽

Tree Phenology ◽

Hass Avocado ◽

N Demand

Effects of nitrogen (N) fertilizer application times and rates on ‘Hass’ avocado (Persea americana) yield and fruit size were determined to resolve whether a single dose of soil-applied N [1x N (25 lb/acre)] at each of the five key stages of tree phenology (January, April, July, August, and November) (control) was as efficacious as soil-applied 2x N (50 lb/acre) at one or two key stages or soil- or foliar-applied 3x N (75 lb/acre) at only one stage. All trees received soil-applied N at 125 lb/acre as ammonium nitrate (NH4NO3) annually; trees receiving 2x or 3x N received the remaining N divided evenly at the same phenological stages (months) as trees receiving five 1x N applications. The importance of supplying N during the summer, when June drop, exponential fruit growth, vegetative shoot growth, and floral initiation occur, was determined by testing soil-applied 0.8x N in July plus August only (40 lb/acre N as NH4NO3 annually). Application time proved an important determinant of total yield. Yield of commercially valuable size (CVS) fruit was correlated with total yield (r = 0.80, P < 0.0001). Four-year cumulative total yields were equal for trees receiving soil-applied 1x N at five key phenological stages and trees receiving soil-applied 2x N in April and 18.75 lb/acre N at the four other stages (months). However, trees receiving soil-applied 2x N in April plus November and only 8.3 lb/acre N in the three other months, in particular July and August, had significantly lower 4-year cumulative total yields (P = 0.0362). Additional evidence of the importance of meeting avocado tree N demand in the summer is that trees receiving only 40 lb/acre N split in July plus August produced 4-year cumulative total yields equal to trees receiving 25 lb/acre N at the five key phenological stages; lower annual N would reduce fertilizer expense and protect the environment.

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

Scientia Horticulturae ◽

10.1016/0304-4238(93)90015-i ◽

1993 ◽

Vol 56 (2) ◽

pp. 147-156 ◽

Cited By ~ 10

Author(s):

T.Grant Thorp ◽

Margaret Sedgley

Keyword(s):

Shoot Growth ◽

Fruit Set ◽

Growth Patterns ◽

Persea Americana ◽

Hass Avocado

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Carbohydrate and boron content of styles of ‘Hass’ avocado ( Persea americana Mill.) flowers at anthesis can affect final fruit set

Scientia Horticulturae ◽

10.1016/j.scienta.2015.11.011 ◽

2016 ◽

Vol 198 ◽

pp. 125-131 ◽

Cited By ~ 11

Author(s):

H.L. Boldingh ◽

M.L. Alcaraz ◽

T.G. Thorp ◽

P.E.H. Minchin ◽

N. Gould ◽

...

Keyword(s):

Boron Content ◽

Fruit Set ◽

Persea Americana ◽

Hass Avocado

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EFFECTS OF HYDROGEN CYANAMIDE ON APPLE AND PLUM FRUIT THINNING

HortScience ◽

10.21273/hortsci.27.6.690a ◽

1992 ◽

Vol 27 (6) ◽

pp. 690a-690

Author(s):

Esmaeil Fallahi ◽

Brenda R. Simons ◽

John K. Fellman ◽

W. Michael Colt

Keyword(s):

Malus Domestica ◽

Fruit Set ◽

Fruit Size ◽

Apple Fruit ◽

Fruit Weight ◽

Full Bloom ◽

Hydrogen Cyanamide ◽

Fruit Thinning ◽

Prunus Salicina

Influence of various concentrations of hydrogen cyanamide (HC) on fruit thinning of `Rome Beauty' apple (Malus domestica Borkh.), `Friar,' and `Simka' plums (Prunus salicina Lindley) were studied. A full bloom application of HC at all tested concentrations decreased `Rome Beauty' apple fruit set and yield, and increased fruit weight. Hydrogen cyanamide at 0.25% (V/V) resulted in adequate apple thinning, indicated by the production of an ideal fruit weight. Prebloom and full bloom applications of HC at greater than 0.75% reduced plum fruit set and yield in `Friar.' Full bloom application of HC at 0.25% to 0.50% showed a satisfactory fruit set, yield, and fruit size in `Friar' plum. Full bloom application decreased fruit set and yield in `Simka' plum. Hand thinning, as well as chemical thinning, is recommended for plums.

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Regulating Budbreak, Flowering, and Fruit Maturity in Sweet Cherry (Prunus avium L.) cv. `Bing' by Surfactant and Nitrate Applications

HortScience ◽

10.21273/hortsci.31.4.603e ◽

1996 ◽

Vol 31 (4) ◽

pp. 603e-603

Author(s):

K.G. Weis ◽

S.M. Southwick ◽

J.T. Yeager ◽

W.W. Coates ◽

Michael E. Rupert

Keyword(s):

Sweet Cherry ◽

Prunus Avium ◽

Fruit Set ◽

Fruit Size ◽

Calcium Nitrate ◽

Potassium Nitrate ◽

Fruit Weight ◽

Full Bloom ◽

Fruit Maturity ◽

Flower And Fruit Development

The years 1995 and 1996 were low chill years in California with respect to stone fruit dormancy. Advancing reproductive budbreak and flowering was accomplished in `Bing' cherry (Prunus avium) by single-spray treatments of a surfactant {a polymeric alkoxylated fatty amine [N,N-bis 2-(omega-hydroxypolyoxyethylene/polyoxypropylene) ethyl alkylamine]} and potassium nitrate in combination when applied at “tightbud,” ≈ 42 days (1 Feb. 1995) before full bloom and with surfactant and potassium nitrate in combination when 10% green calyx was apparent, 33 days before full bloom. Applying 2% surfactant (v/v) + 6% potassium nitrate (w/v) was most effective in advancing bloom, speeding progression through bloom, and advancing fruit maturity when applied at tightbud stage. Surfactant (2% or 4%) applied with 25% or 35% calcium nitrate (w/v) on 2 Feb. 1996 significantly advanced full bloom compared to nontreated controls. Fruit maturity (1995) was somewhat advanced by surfactant–nitrate treatments, but fruit set and final fruit weight were equivalent among treatments. No phytotoxicity was noted in foliage or fruit. In California, marginal and insufficient winter chilling often causes irregular, extended, or delayed bloom periods, resulting in poor bloom-overlap with pollenizers. As a result, flower and fruit development may be so variable as to have small, green and ripe fruit on the same tree, making harvest more time consuming and costly. Data indicate that this surfactant, in combination with a nitrogenous compound, has potential to advance reproductive budbreak and advance maturity in sweet cherry without reducing fruit set or fruit size. Advancing the ripening time of sweet cherry even 2 to 3 days can increase the price received per 8.2-kg box by $10 to $20.

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Pruning Height and Selective Limb Removal Affect Yield of Large 'Hass' Avocado Trees

HortScience ◽

10.21273/hortsci.36.4.699 ◽

2001 ◽

Vol 36 (4) ◽

pp. 699-702 ◽

Cited By ~ 4

Author(s):

T.G. Thorp ◽

B. Stowell

Keyword(s):

Large Volume ◽

Fruit Size ◽

Persea Americana ◽

Small Tree ◽

Harvest Efficiency ◽

Hass Avocado ◽

And Control

Avocado (Persea americana Mill. cv. Hass) trees were pruned over 3 years at either 4 or 6 m in height by removing or heading back selected limbs. Yields were compared with those from control trees with no pruning in the upper canopy. All trees had similar crop loads before pruning. Trees were at 9 × 10-m spacing and were 8 years old when first pruned. Fruit yields were recorded for 2 years before the first pruning and then in each year of pruning. In the final year, trees were harvested in four height zones: 0-2m; 2-4 m; 4-6 m; and >6 m. Cumulative yields over 3 years were similar on 6-m and control trees, but were less on 4-m trees due to the large volume of fruiting canopy removed in the first pruning. The height of the main fruiting zone was lowered on the 4-m trees, with yields in the 2-4-m zone similar to those in the 4-6-m zone of the control trees. Pruning to reduce the number and length of scaffold branches increased fruit yields on the remaining scaffolds without reducing fruit size. Results are discussed in terms of harvest efficiency and the benefits of small tree orchard systems.

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EFFECTS OF HYDROGEN CYANAMIDE ON STONE FRUIT THINNING

HortScience ◽

10.21273/hortsci.25.9.1122a ◽

1990 ◽

Vol 25 (9) ◽

pp. 1122a-1122

Author(s):

Esmaeil Fallahi ◽

Michael Colt ◽

S. Krishna Mohan ◽

John Fellman

Keyword(s):

Fruit Set ◽

Fruit Size ◽

Stone Fruit ◽

Severe Toxicity ◽

Full Bloom ◽

Hydrogen Cyanamide ◽

Fruit Number ◽

Fruit Thinning

Influence of prebloom and full bloom applications of hydrogen cyanamide on `Simka' and `Friar' plums in Southwest Idaho and `Florda Prince' peach in Southwest Arizona was studied. Prebloom application of 0.5% hydrogen cyanamide caused severe toxicity to the fruit buds in `Friar' lure, while 2% hydrogen cyanamide did not cause toxicity in `Simka' plum. `Simka' fruit was effectively thinned with 1-2% prebloom application. At full bloom, 1.5% hydrogen cyanamide caused severe flower and leaf burning in both `Friar' and `Simka' plums, while concentrations between 0.1% and 1% thinned flowers (fruits) in both of the plum cultivars. Influence of hydrogen cyanamide on final fruit set, fruit size and maturity are also studied. Prebloom or full bloom applications of 2% or 3% hydrogen cyanamide eliminated 95 to 100% of the blooms, while application of this chemical at 1% sufficiently thinned the fruit. Number of commercially packed large peaches in trees receiving 1% hydrogen cyanamide was the same as that in trees thinned by hand, suggesting hydrogen cyanamide as a potential chemical for stone fruit thinning.

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The Relationship Between Flower and Fruit Abscission and Alternate Bearing of ‘Hass’ Avocado

Journal of the American Society for Horticultural Science ◽

10.21273/jashs.133.1.3 ◽

2008 ◽

Vol 133 (1) ◽

pp. 3-10 ◽

Cited By ~ 28

Author(s):

Lauren C. Garner ◽

Carol J. Lovatt

Keyword(s):

Developmental Stages ◽

Weather Conditions ◽

Nutrient Status ◽

Persea Americana ◽

Alternate Bearing ◽

Immature Fruit ◽

Fruit Abscission ◽

Reproductive Structures ◽

Independent Process ◽

Hass Avocado

Despite profuse flowering, ‘Hass’ avocado (Persea americana Mill.) yields are low because of excessive flower and fruit abscission. Whether the dynamics of flower and fruit abscission are influenced by or contribute to alternate bearing, the production of a heavy on-crop followed by a light off-crop that is characteristic of many avocado cultivars, remains unresolved. The objective of this research was to determine whether abscission of reproductive structures from ‘Hass’ avocado trees during specific developmental stages, including flowering, fruit development, and fruit maturity, was influenced by crop status of the current or preceding year. Abscised reproductive structures were collected from commercially bearing trees during two complete crop years. Flower abscission began at about the same time but peaked 1 month later in the off-crop year compared with the on-crop year. Peak abscission rates were lower during the off-crop year than the on-crop year (compare 1836 ± 403 to 5378 ± 856 flowers per day and 50 ± 18 to 280 ± 23 immature fruit per day, respectively). The off- or on-crop status of the tree did not influence the percentage fruit set, average fruit diameter, or biomass of individual fruit that abscised at similar phenological stages. Furthermore, flower and fruit abscission were not influenced by the number of mature fruit from the previous year's crop. In both years of the research, as immature fruit abscission declined, abscission of the preceding year's crop increased, indicating that the processes were controlled independently. During the study, neither weather conditions nor tree nutrient status were associated with key abscission events. Taken together, these results provide evidence that the previous year's yield does not influence flower or fruit abscission and the seasonal abscission of reproductive structures is an independent process that does not contribute to alternate bearing of ‘Hass’ avocado.

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