Abstract
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 (NH 4 NO 3 ) 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 NH 4 NO 3 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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Claims 5
Claim · model-written summary
Application time was an important determinant of total yield.
Not reportedDirection
Verbatim
e0“Application time proved an important determinant of total yield.”
t0“‘Hass’ Avocado”
Claim · model-written summary
Commercially valuable size fruit yield correlated with total yield.
- Taxon
- ‘Hass’ Avocadot0
- Outcome
- Yield of commercially valuable size (CVS) fruite0
- Value
- r = 0.80e0
- Comparator
- total yielde0
Not reportedDirection
Verbatim
e0“Yield of commercially valuable size (CVS) fruit was correlated with total yield ( r = 0.80, P < 0.0001).”
t0“‘Hass’ Avocado”
Claim · model-written summary
Four-year cumulative total yields were equal under five 1x applications and 2x in April plus lower doses at other stages.
Verbatim
e0“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).”
t0“‘Hass’ Avocado”
Claim · model-written summary
The April plus November 2x schedule lowered four-year cumulative yield.
- Taxon
- ‘Hass’ Avocadot0
- Treatment
- soil-applied 2x N in April plus November and only 8.3 lb/acre N in the three other monthse0
- Outcome
- 4-year cumulative total yieldse0
- Direction
- lowere0
- Value
- P = 0.0362e0
Not reportedComparator
Verbatim
e0“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).”
t0“‘Hass’ Avocado”
Claim · model-written summary
Forty pounds per acre split between July and August gave equal cumulative yield to five 25 pound applications.
Verbatim
e0“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”
t0“‘Hass’ Avocado”