Nitrogen Management for Organic Strawberry Production

Update

Mark Gaskell, Farm AdvisorUC Cooperative Extension- San Luis Obispo

Overview

• Nitrogen is critical limiting factor

• Certified organic N more costly, uncertain

• N mineralization determines nitrate availability

• Different materials with varying availability

• Field management also critical- nitrate moves with water

http://www.ams.usda.gov/AMSv1.0/nop

http://www.omri.org/

0 4 1412 6 10 8 18 16 2 20

.

Mineralization of Pre-plant Applied Compost

Time

Rate

of N

Min

eral

izatio

n or

abs

orpt

ion

Week

0 4 1412

6 10 8 18 16 2 20

Time

Week

.

Mineralization of Pre-plant Applied Compost

Rate

of N

Min

eral

izatio

n or

abs

orpt

ion Plant N Demand

0 4 1412

6 10 8 18 16 2 20

SouthernDistricts

Northern

Districts

Time

Week

. . ..

Periodic injections needed – weekly?

Mineralization of Pre-plant Applied Compost

Rate

of N

Min

eral

izatio

n or

abs

orpt

ion

Plant N Demand

Source- Tim Hartz, UC-Davis

Source- Tim Hartz, UC-Davis

Some materials relatively high in available N in greenhouse

0

20

40

60

80

100

120St

raw

berr

y N

Acc

umul

atio

n(lb

N/A

)Strawberry Nitrogen Accumulation

Plant N

Plant plus Fruit N

0

10

20

30

40

50

60R

esid

ual S

oil N

itrat

e-N

(ppm

)

Sample Date (2007/8)

True Organic

Neptunes Harvest

Phytamin 434

0

10

20

30

40

50

60S

oil R

esid

ual N

itrat

e-N

(ppm

)

Sample Date (2007 / 2008)

6.8 kg N /week

13.6 kg N / week

20.4 kg N /week

0

10

20

30

40

50

60

Res

idua

l Soi

l Nitr

ate-

N (p

pm)

Sample Date (2007/8)

True Organic

Neptunes Harvest

Phytamin 434

0

10

20

30

40

50

60

Res

idua

l Soi

l Nitr

ate-

N (p

pm)

Sample Date (2007 / 2008)

125 lb N Preplant

2.5 lb N /week

IllustrativeSeasonal Soil N in Conventional Field

Illustrative Seasonal Soil N in Organic Field

N uptake rate VS Timing of N availability

• Total N uptake important

• Strawberries? Early vegetative development?

• Sets stage for plant branch number, size

• Can have big effect on yield

0

10

20

30

40

50

60S

oil R

esid

ual N

itrat

e-N

(ppm

)

Sample Date (2007 / 2008)

6.8 kg N /week

13.6 kg N / week

20.4 kg N /week

0

10

20

30

40

50

60

70

Sampling Date

Weekly Soil Nitrate-N following varying rates ofpreplant and weekly injected organic N

10-3

10-6

0

10

20

30

40

50

60

()

Sampling Date

Weekly Soil Nitrate-N following varying rates ofpreplant and weekly injected organic N

0-3

5-3

10-3

Organic Fruit Yields?

• Typically half of conventional yields

• Rarely different among treatments• Preplant compost rates• in-season injection materials?• In-season injection rates

Are we applying N early enough and managing injections to assure N is available?

0

500

1000

1500

2000

2500

3000

3500

4000To

tal F

ruit

Yiel

d (K

g / h

a)

True OrganicNeptune'sPhytamin 434

2008 Season

Summary

• N fertilization is challenging in organic production

• Low OM soils more difficult and costly

• Materials vary in cost, N availability

• Mineralization determines nitrate availability

• Lower N compared to conventional- management can be critical - interaction with water management?

Acknowledgements

• Cachuma Resource Conservation District

Kate Dixon, Julie Fallon, Claire Wineman,Misael Sanchez, Kevin Peterson, Adriana Morales,

Tom Lockhart

• Dave Peck, Manzanita Farms / Well Pict- Santa Maria

• CalPoly San Luis Obispo – Soil Science Dept

• USDA – Section 2501 Program