Abstract
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 NH 4 NO 3 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 NH 4 NO 3 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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Claims 11
Claim · model-written summary
A November double dose increased four-year cumulative yield by 30%.
- Taxon
- Avocado
Persea americanat0 - Treatment
- N application at 56 kg·ha -1e0
- Outcome
- 4-year cumulative yielde0
- Direction
- increasede0
- Value
- 30%e0
- Comparator
- control treese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“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).”
t0“Avocado”
Claim · model-written summary
An April double dose increased four-year cumulative yield by 39%.
- Taxon
- AvocadoPersea americanat0
- Treatment
- N application at 56 kg·ha -1e0
- Outcome
- 4-year cumulative yielde0
- Direction
- increasede0
- Value
- 39%e0
- Comparator
- control treese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“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).”
t0“Avocado”
Claim · model-written summary
More than 70% of the net yield increase was large fruit.
- Taxon
- AvocadoPersea americanat0
- Outcome
- net increase in yield was commercially valuable large size fruite0
- Value
- more than 70%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In each case, more than 70% of the net increase in yield was commercially valuable large size fruit (178 to 325 g/fruit).”
t0“Avocado”
Claim · model-written summary
Double-dose nitrogen at either stage increased the weight and number of large fruit.
- Taxon
- AvocadoPersea americanat0
- Treatment
- double dose of Ne0
- Outcome
- kilograms and number of large size fruite0
- Direction
- greatere0
- Comparator
- control treese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“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).”
t0“Avocado”
Claim · model-written summary
Only November double-dose nitrogen increased four-year average yield.
- Taxon
- AvocadoPersea americanat0
- Treatment
- November treatmente0
- Outcome
- yielde0
- Direction
- increasede0
- Comparator
- control treese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Averaged across the 4 years of the study, only the November treatment increased yield compared to the control trees ( P ≤ 0.05).”
t0“Avocado”
Claim · model-written summary
January double-dose nitrogen did not significantly affect average or cumulative yield or fruit size.
- Taxon
- AvocadoPersea americanat0
- Treatment
- double dose of N at flower initiation (January)e0
- Outcome
- average or cumulative yield or fruit sizee0
- Direction
- no significant effecte0
- Comparator
- control treese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“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.”
t0“Avocado”
Claim · model-written summary
February double-dose nitrogen did not significantly affect average or cumulative yield or fruit size.
- Taxon
- AvocadoPersea americanat0
- Treatment
- during early-stage gynoecium development (February)e0
- Outcome
- average or cumulative yield or fruit sizee0
- Direction
- no significant effecte0
- Comparator
- control treese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“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.”
t0“Avocado”
Claim · model-written summary
June double-dose nitrogen did not significantly affect average or cumulative yield or fruit size.
- Taxon
- AvocadoPersea americanat0
- Treatment
- during June drope0
- Outcome
- average or cumulative yield or fruit sizee0
- Direction
- no significant effecte0
- Comparator
- control treese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“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.”
t0“Avocado”
Claim · model-written summary
April double-dose nitrogen reduced alternate bearing severity.
- Taxon
- AvocadoPersea americanat0
- Treatment
- double dose of N in Aprile0
- Outcome
- severity of alternate bearinge0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Application of the double dose of N in April significantly reduced the severity of alternate bearing ( P ≤ 0.05).”
t0“Avocado”
Claim · model-written summary
Yield was not significantly correlated with leaf nitrogen concentration.
- Taxon
- AvocadoPersea americanat0
- Organ / stage
- leafe0
- Compound
- Ne0
- Outcome
- Yielde0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Yield was not significantly correlated with leaf N concentration.”
t0“Avocado”
Claim · model-written summary
At equal nitrogen amounts, application timing was more important than application rate.
- Taxon
- AvocadoPersea americanat0
- Treatment
- time of applicatione0
- Outcome
- more important factore0
- Direction
- more importante0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When the amounts of N applied were equal (196 kg·ha -1 ), time of application was the more important factor.”
t0“Avocado”
The same questions in other papers
nitrogen · yield · Persea americana (avocado)Results agree
4 papers in the same direction as this paper
- positive
- positive
- positive
1 paper more in this group
See all 5 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.