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Soil fertility management for
pepper production
lbs per acre
20 - 30
40 - 60
P2O5
120 - 18080 - 110fruit content
240 - 320 200 - 260total plant content
K2ON
Typical nutrient uptake by a bell pepper crop
producing 50,000 lb of fruit/acre :
Common soil tests for P availability :
Olsen (bicarbonate) test - extraction in sodium bicarbonate at pH 8.5
best method if soil pH > 6.5
Bray test - extraction in dilute acid
useful in acidic soil (pH < 6.5)
§ Represents ‘available’ P, not total P
§ Bray values higher than Olsen in most cases
Phosphorus requirement for pepper :
Does the Olsen test measure plant-available P ?
Bio-available P (anion membrane) technique
0.0
2.0
4.0
6.0
8.0
0 50 100 150 200
Olsen P (PPM)
Anion resin P
(ug/cm2)
r = 0.89
Bio-available P vs. Olsen P :
30 California soils in vegetable rotations
Temperature affects soil P bioavailability :
0
1
2
3
4
5
6
7
8
29 76 85 142 177
Soil Olsen P level (PPM)
Anion resin extractable P
(ug/cm2)
5 C = 41 F
15 C = 59 F
25 C = 77 F
On average, each 10 oF increase in soil temperature increases
bioavailable P by ≈ 20%
High Low
Lettuce
Potato
Pepper?
Tomato
Soil P availability requirement :
Is P application always necessary ?
What application rate is reasonable ?
Soil P availability requirement :
Is P application always necessary ?
What application rate is reasonable ?
Agronomic threshold
(Olsen test)
High Low
Lettuce
Potato
Pepper?
Tomato
60 PPM 20 PPM
positive crop response unlikely> 40 PPM
positive response likely, especially
in cold soil
20 - 40 PPM
positive response guaranteed < 20 PPM
Pepper response to applied POlsen P level
positive crop response unlikely> 40 PPM
positive response possible, especially
in cold soil
20 - 40 PPM
positive response guaranteed < 20 PPM
Pepper response to applied POlsen P level
Application rate ?• limit application to crop removal rate in fields with high soil P
• rates > 120-150 lb P2O5/acre questionable, regardless of
soil test level
Nitrogen management :
Ø Crop N uptake is predictable by growth stage
lb N per acre per day:
< 1 4 - 5 < 3
Nitrogen management :
Ø Crop N uptake is predictable by growth stage
lb N per acre per day:
Ø Not all N needs to come from fertilizer application:
- residual soil NO3-N can be substantial
- soil N mineralization can be up to 1 lb / acre / day
< 1 4 - 5 < 3
Irrigation efficiency and N management :Ø at common soil NO3-N levels during the season, one inch of
leaching may carry 20-30 lb NO3-N/acre out of the root zone
Potassium management :
Ø Crop K uptake is predictable by growth stage
lb N per acre per day:
< 1 4 - 7 < 4
Potassium management :
Ø Crop K uptake is predictable by growth stage
lb N per acre per day:
< 1 4 - 7 < 4
Ø pepper has a moderately high K requirement (240 - 320 lb K2O/acre)
Ø majority of K ends up in fruit
Øleaf K declines to ‘feed’ the fruit; that’s why deficiency shows late
Evaluating soil K supply :
Ø ‘exchangeable’ K, usually expressed as PPM
Ø K as a % of base exchange
[milliequivalent of K / (meq Ca + Mg + Na + K)] x 100
Soil test K interpretation :
Ø fields > 200 PPM exchangeable K, and > 3% of base exchange,
do not require K fertilization
Ø soils < 150 PPM, or < 2% of base exchange, should be fertilized
Ø K fertilization is most effective during fruit set and
early fruit development
http://vric.ucdavis.edu/veg_info_topic/fertilization.htm
Crop monitoring options In-season soil nitrate testing :
ü high root zone soil NO3-N concentration (> 20 PPM) indicate
that additional N application can be postponed
Soil nitrate testing most useful early in the season
Petiole testing as a management tool ?Ø high NO3-N or PO4-P concentration guarantees current sufficiency,
but does not project far into the future
Petiole testing as a management tool ?Ø high NO3-N or PO4-P concentration guarantees current sufficiency,
but does not project far into the future
Ø lower NO3-N or PO4-P concentration does not prove deficiency
2004-05 survey of 75 coastal lettuce fields
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
2 4 6 8 10 12 14 16 18 20
Field
% leaf N Current
sufficiency
threshold
at early heading stage :
Leaf total N of the 20 highest yielding fields…
0
3,000
6,000
9,000
12,000
15,000
2 4 6 8 10 12 14 16 18 20
Field
Midrib NO3-N
(PPM)
Current
sufficiency
threshold
Midrib NO3-N of the 20 highest yielding fields…
at early heading stage :
Tissue sampling in processing tomato :
ü 4 high yield commercial fields
ü UCD fertilizer trial
Tissue sampling in processing tomato :
ü 4 high yield commercial fields
ü UCD fertilizer trial
10
20
30
40
50
60
200 400 600 800 1000 1200
Growing degree days
Leaf N (g kg-1)
field 1
field 2
field 3
field 4
UCD deficient
UCD adequate
UCD excessive
Tissue sampling in processing tomato :
ü 4 high yield commercial fields
ü UCD fertilizer trial
10
20
30
40
50
60
200 400 600 800 1000 1200
Growing degree days
Leaf N (g kg-1)
field 1
field 2
field 3
field 4
UCD deficient
UCD adequate
UCD excessive
0
3,000
6,000
9,000
12,000
15,000
200 400 600 800 1000 1200
Growing degree days
Petiole NO3-N (PPM) field 1
field 2
field 3
field 4
UCD deficient
UCD adequate
UCD excessive
Does petiole testing indicate recent nutrient uptake ?
2007 UC Davis processing tomato trial
Conclusion :Most petiole NO3-N is already in cell vacuoles, and therefore the
concentration is affected by the rate at which the plant converts
nitrate to organic N; factors other than soil nitrate supply
govern that rate
0
200
400
600
800
1,000
1,200
1,400
1,600
4 6 8 10 12 14
Weeks after transplanting
NO3-N
(mg liter-1)
sap
xylem
Calcium disorders :Ø symptoms develop because insufficient Ca is moved into
actively growing cells during fruit development
Calcium disorders :Ø symptoms develop because insufficient Ca is moved into
actively growing cells during fruit development
Ø origin of the problem is the inefficient way plants move Ca into fruit;
soil Ca limitation seldom the primary problem
Calcium disorders :Ø symptoms develop because insufficient Ca is moved into
actively growing cells during fruit development
Ø origin of the problem is the inefficient way plants move Ca into fruit;
soil Ca limitation seldom the primary problem
Ø control by soil or foliar Ca application is minimally effective
How much plant-available calcium
do California soils have ?
15 representative California soils tested
y = 0.20x
r = 0.72
0
50
100
150
200
250
300
0 200 400 600 800 1000 1200
Soil solution Ca (PPM)
Saturated paste Ca
(PPM)
ü most California soils have 100 - 200 lb/acre Ca in solution in the
top foot; as plants remove it, more becomes available
ü at normal application rates, fertilizer Ca only marginally increases
soil Ca supply
0.00
0.10
0.20
0.30
0.40
0 2 4 6
Leaf Ca (%)
Fruit Ca (%)
Processing tomato fruit quality survey, 140 fields :
Calcium doesn’t move into fruit easily :
§ Ca moves in transpirational flow in xylem, so leaf Ca is high
§ Ca does not move in phloem, so fruit Ca is low; surface wax
on fruit makes foliar application questionable
What can be done to minimize calcium disorders ?
ü prevent water stress
ü choose adapted varieties
ü avoid high ammonium levels during early fruit development