periods. Applying additional fertilizer under the following three circumstances
is part of the current UF/IFAS fertilizer recommendations and thus BMPs.
Supplemental N and K fertilizer applications may be made if 1) grown on
bare ground with seepage irrigation, a 30 lbs/A of N and/or 20 lbs/A of K2O
supplemental application is allowed after a leaching rain. A leaching rain
occurs when it rains at least 3 inches in 3 days, or 4 inches in 7 days; 2)
For bare ground production, the supplemental amount allowed is 30 lbs/A of
N and/or 20 lbs/A of K2O. For drip irrigated crops, the supplemental amount
allowed is 1.5 to 2.0 lbs /A/day for N and/or K2O for one week; or 3) for economic
reasons, the harvest period has to be longer than the typical harvest
period. When the results of tissue analysis and/or petiole testing are below
2O
may be made for each additional harvest for bare ground production. For
drip-irrigated crops, the supplemental fertilizer application is 1.5 to 2.0 lbs/A/
day for N and/or K2O until the next harvest.
FERTIGATION
Common irrigation systems used for fertigation include drip, sprinkler,
and pivot systems. Advantages of fertigation over conventional fertiliz-
and 4) lower application cost. Liquid and water-soluble fertilizers are more
commonly used for fertigation than dry fertilizers. The most common liquid N
fertilizers for fertigation are ammonium nitrate (20-0-0), calcium ammonium
nitrate (17-0-0), and urea ammonium nitrate (32-0-0). Complete fertilizers
(e.g. 8-8-8 and 4-10-10) are also commonly used. In commercial vegetable
production of South Florida, a formula of 4-0-8 or 3-0-10 is the most common
in fertigation. To develop a more precise fertilizer application strategy,
growers can request a custom blend at a local fertilizer dealer based on soil
test results and crop nutrient requirements. For more information, consult
“Fertigation Nutrient Sources and Application Considerations for Citrus” at
<>.
The basic components for a fertigation system include a fertilizer tank,
prevention device. All of the components must be resistant to corrosion.
In most situations, N and K are the nutrients injected through the irrigation
tube. Split applications of N and K through the irrigation system offers a
means to capture management potential and reduce leaching losses. Other
nutrients, such as P, are usually applied to the soil rather than by injection.
This is because chemical precipitation can occur with these nutrients and
the high calcium carbonate content of our irrigation water in Florida.
Table 2.8. Fertigation1 and supplemental fertilizer1 recommendations on mineral soils testing low in potassium (K2O) based on the MEHLICH 3 SOIL EXTRACTION METHOD.
Preplant2
(lb/A)
Injected3
(lb/A/day)
Low plant
content4,5
Extended season4,6
(lb/A/day)
Eggplant
Wk after transplanting7 1-2 3-4 5-10 11-13
N 0-70 1.5 2.0 2.5 2.0 1.5-2.0 1.5-2.0
K2O 0-55 1.0 1.5 2.5 1.5 1.5-2.0 1.5-2.0
Okra
Wk after transplanting 1-2 3-4 5-12 13
N 0-40 1.0 1.5 2.0 1.5 1.5-2.0 1.5-2.0
K2O 0-50 1.0 1.5 2.0 1.5 1.5-2.0 1.5-2.0
Pepper
Wk after transplanting 1-2 3-4 5-11 12 13
N 0-70 1.5 2.0 2.5 2.0 1.5 1.5-2.0 1.5-2.0
K2O 0-70 1.5 2.0 2.5 2.0 1.5 1.5-2.0 1.5-2.0
Strawberry
Wk after transplanting 1-2 Sept.-Jan. Feb.-Mar. Apr.
N 0-40 0.3 0.6 0.75 0.6 0.6-0.75 0.6-0.75
K2O 0-40 0.3 0.5 0.75 0.6 0.6-0.75 0.6-0.75
Tomato8
Wk after transplanting 1-2 3-4 5-11 12 13
N 0-70 1.5 2.0 2.5 2.0 1.5 1.5-2.0 1.5-2.0
K2O 0-70 1.5 2.0 2.5 2.0 1.5 1.5-2.0 1.5-2.0
1
at a rate no greater than 10 to 15 lb/A for N and P2O5 and applied through the plant hole or near the seeds.
2
double/triple crops because of the plastic mulch; hence, in these cases, all the fertilizer has to be injected.
3 This fertigation schedule is applicable when no N and K20 are applied preplant. Reduce schedule proportionally to the amount of N and K20 applied preplant. Fertilizer
4 Plant nutritional status may be determined with tissue analysis or fresh petiole-sap testing, or any other calibrated method. The “low” diagnosis needs to be based on UF/
IFAS interpretative thresholds.
5 Plant nutritional status must be diagnosed every week to repeat supplemental fertilizer application.
6 Supplemental fertilizer applications are allowed when irrigation is scheduled following a recommended method (see “Evapotranspiration-based Irrigation Scheduling for
to be applied ‘in advance’ with the preplant fertilizer.
7 For standard 13 week-long, transplanted tomato crop.
8 Some of the fertilizer may be applied with a fertilizer wheel through the plastic mulch during the tomato crop when only part of the recommended base rate is applied
preplant. Rate may be reduced when a controlled-release fertilizer source is used.
8 2019 Vegetable Production Handbook of Florida