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