12/16/2015

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Nitrogen Management in Organic Strawberries: Challenges and Approaches

Joji Muramoto and Carol Shennan, University of California Santa Cruz Mark Gaskell, UC Cooperative Extension

December 16, 2015

http://www.extension.org/organic_production

Joji Muramoto Carol Shennan Mark Gaskell UCSC UCSC UC Cooperative Extension

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Nitrogen Management in Organic Strawberries: challenges and approaches

Joji Muramoto1, Carol Shennan1 and Mark Gaskell2

1 University of California, Santa Cruz 2University of California Cooperative Extension San Luis Obispo and Santa Barbara Cos., CA. (USA)

Overview

1. Organic Strawberry Production in California (CA) 2. Nitrogen (N) Management in Organic Strawberries a. Synchronizing N Supply with Plant N Demand b. Challenges for N Management in Organic Strawberries in CA c. N Uptake by Organic Strawberries d. N Supply for Organic Strawberries 3. Efficiency Trial 4. Pre-plant/In-season N Field Trials in the Northern District 5. Summary 6. Future Studies

California Strawberry Production Districts

Northern (Watsonville/Salinas) California produces: • ~25% of world strawberry production (FAO, 2012) • ~85% of US production • 38,100 acres in 2015 Central Southern (Santa Maria) (Oxnard)

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Mediterranean climate Santa Cruz, CA with mild and dry 300 (1980-2010 Normal) summer allows the 30 year -long strawberry 250 Max. production in CA 20 200 Ave. temp. Air

Moderate summer Min. 10 150

temperatures permit ° C harvest over extended 0 Precip. mmPrecip. 100 season

50 -10

0 -20

Month

Overview of annual strawberry cropping in California

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Organic Strawberry Production in California

• 3,430 acres in 2015 Organic Strawberry Acreage (9% of total strawberry Acres acreage in CA) 4,000 3430

• Marketable fruit yield 28,000 3,000 – 40,000 lb / ac 2,000 1794 (40-60 % of conventional 1667 yield) 1,000 297 541 0 2000 2005 2010 2015 Year

(California Strawberry Commission 2015)

Nitrogen: A key to crop production

• Primary nutrient limiting plant growth

- + • Inorganic (nitrate NO3 or ammonium NH4 ) or organic form in soil

• Organic N has to be mineralized to inorganic forms to be absorbed by most crops

• Rapid turnover in soil microbial activity nitrate is soluble in water - moves readily in soil solution but susceptible to leaching

Synchronizing Nitrogen Supply with Nitrogen Demand

• Matching N supply with N demand of strawberry plants - amount and timing

Available for loss • Important for: • Efficient use of N resource • Protect ground and surface water from nitrate Asynchrony of N supply and N demand • Reduce N cost (Robertson, 1997) • Critical for strawberry yield

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Challenges for N management in organic strawberries in CA

• Extended harvest season

Dec.- June (So. dist.), Feb.- Aug (Central), March-Nov. (No. dist.)

– day neutral varieties may be cutback for year around harvest

• Variable soil organic matter and unpredictable SOM mineralization

• Release from pre-plant incorporated organic material does not coincide with plant demand

• Leaching of N with winter rains.

Asynchrony of N supply and N demand in an organic strawberry field in the Northern region, CA Precipitation N lb/ac inches Post broccoli residue incorporation 300 and preplant N application 60

Soil inorg . N in 00’-30cm-1’ depthdepth 250 502.0

200 40

N uptake by strawberry plants 150 30 Residual inorganic N at 1.0 broccoli harvest Precipitation 100 20

50 10

0 0 -Sep.7 Nov.0 Jan.7 Mar.14 Apr.21 June29 Aug.36 Sep.43 Weeks after planting (Muramoto et al., 2004)

Challenges for N management in organic strawberries in CA (continued)

• Low soil organic matter (SOM) sandy soil in some areas

• Limited options for manipulation of SOM

• Limited rotation / green alternatives in typical strawberry cropping system

• Problems with efficient in-season fertigation

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N Demand: Cumulative N Uptake by Organic Strawberry

Marketable yield: 18.9 tons/acre Strawberry N uptake: near Watsonville, CA. Average of 4 seasons. Slow but constant for long period cv. Aromas (Muramoto and Gaskell, 2011)

N uptake by conventional strawberries in California

Santa Maria

Watsonville

(Bottoms et al., 2013)

N Supply: Organic N sources

• Traditionally, organic growers concentrate on soil organic matter (SOM) management as basis for organic production program

• N mineralization residue, or lasts 8-10 weeks - does not match the N needs of the strawberry crop

• Cycling of N in soil organic fraction, microbial activity - dynamic – depends on environmental conditions

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Net N mineralization (% of total N) from organic and

Material Total N C/N 1 week 4 weeks 8 weeks 24 weeks % ratio Blood meal 15.8 3.1 51 67 70 - Feather meal 14.2 3.5 50 64 63 - Fish powder 13.7 3.4 48 60 64 - Sea bird 11.1 1.3 45 48 54 - Pelletized poultry 2.8 8.6 10 23 36 - manure Manure (poultry, feedlot) 2.7 11 - - - 15 Manure compost 1.9 9.8 - - - 6 (poultry, feedlot, dairy) Plant residue compost 1.6 14.2 - - - 2

Incubated at 77 °F. (Hartz and Johnstone 2004; Hartz et al., 2000)

N release from SOM

• SOM can also provide some N to plants, but not sufficient.

• Increasing long-term SOM. not economical < 1%

source - Nitrogen NutriFacts, International Institute, 2015

Asynchrony of pre-plant nitrogen release and strawberry N uptake

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N Supply via fertigation

Plant N demand Mineralization from pre-plant compost Southern Districts

or or absorption Northern Districts

0 2 4 6 8 10 12 14 16 18 20 22 24

Week Rate of N release release Nof Rate

Time

N Supply: Need of In-season N applications

• In-season band application and cultivation with organic pelleted or milled fertilizer…impractical under plasticulture CA strawberry systems

• Fertigation: liquid organic fertilizer applications via drip tapes are popular among organic strawberry growers in CA….but some issues

Anecdotal data for poor fertigation performance

• “Small plants” and lower yields relative to conventional fields

• Rapid plugging of system filters

• Little or no effects on soil N or yield from varying rate field trials

• Early deterioration of distribution uniformity

• Low tissue N test regardless of fertigation in organic strawberries

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Field trails to quantify N applied via fertigation with organic fertilizer materials

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Total nitrogen passing emitters (lb/A) during 1 hr fertigation (injection above filter)

Total nitrogen passing emitters (lb/A) during 1 hr fertigation (injection below filter)

Pre-plant/In-season N Trials in the Northern District

• Goal: To examine effects of types and rates of pre-plant and in-season N applications to fruit yield and N dynamics in organic strawberry production

• Approach: Four seasons of randomized block split-plot on-farm trials with In-season N as main plots and pre-plant N as split plots in Watsonville, CA (4 reps)

• Monitored fruit yield, soil inorganic N (0”-12” depth), plant biomass N • cv. Seascape

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Experimental Design

Season Main plots Split plots Site (In-season N*) (Pre-plant N) 2005-06 50, 100, 150 lb-N/ac Sudan grass (SG) Site-1** with liquid organic fertilizer SG + Feather meal 50 lb-N/ac (SG+FM) SG + Compost 5 t/ac (SG+CP) 2006-07 75, 150, 225 lb-N/ac None (0) Site-2** with liquid organic fertilizer Sudan grass (SG) Compost 10 t/ac (CP)

* Biweekly applications through Mar. to Oct. ** Managed by a small scale diversified grower Grower’s standard practice.

Marketable Fruit Yield (Mean ± SEM)

Mkt: ANOVA (P≤0.05) Mkt: ANOVA (P≤0.05) In-season: n.s. 2005-06 (Site-1) In-season: n.s. 2006-07 (Site-2) Pre-plant: n.s. Pre-plant: n.s. In-season x Pre-plant: n.s. In-season x Pre-plant: n.s. Typical local organic yield range (Bolda et al., 2006)

40,000 40,000

30,000 30,000

20,000 20,000

Marketable fruit yield lb/acyieldfruit Marketable Marketable fruit yield lb/acyieldfruit Marketable

10,000 10,000

0 0

0 0

Pre-plant 0

SG SG SG

CP CP CP

SG SG Pre-plant SG

In-season

SG+CP SG+CP

SG+CP 75 lbs-N 150 lbs-N 225 lbs-N

SG+FM SG+FM SG+FM In-season 50 lbs-N 100 lbs-N 150 lbs-N

Soil Inorganic N (0’-1’ depth)

2005-06 (Site-1) 2006-07 (Site-2) 50-SG 75-0 Pre: * 50-SG+FM 75-SG 168150 50-SG+CP 168150 75-CP 100-SG 150-0 100-SG+FM 150-SG 100-SG+CP 150-CP 150-SG 225-0 150-SG+FM 225-SG 150-SG+CP 225-CP

112100 112100

N N lb/ac N lb/ac

5650 5650 Pre: * Pre: ** In-seas: *

Pre: * in-seas. x Pre: *

00 00 Jul-05 Oct-05 Jan-06 May-06 Aug-06 Nov-06 Jul-06 Oct-06 Jan-07 Apr-07 Aug-07 Nov-07

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Plant N Uptake (Plant + Harvested Fruits)

75-0 2005-06 (Site-1) 50-SG 2006-07 (Site-2) 75-SG 50-SG+FM 75-CP 50-SG+CP 150-0 168150 100-SG 168150 150-SG 100-SG+FM 150-CP 100-SG+CP 225-0 150-SG 225-SG 150-SG+FM 225-CP 150-SG+CP

112100 112100

N N lb/ac N N lb/ac

In-seas. **

5650 5650

00 00 Oct-05 Jan-06 May-06 Aug-06 Nov-06 Oct-06 Jan-07 Apr-07 Aug-07 Nov-07

160 N Dynamics in In-season100 lb-N/ac + Sudan Grass + Feather Meal Plot in the 2005-06 Season (Site-1)

140 Soil inorganic N Apparent N loss = A – B = 100 lb-N/ac 120 (0’-1’ depth) (incl. leaching, denitrification, run off, and immobilization)

100

80 A 60 Precip. Plant N uptake mm 40

20 B 0 20 wks from the transplanting

160 N Dynamics in In-season 75 lb-N/ac + Sudan Grass Plot in the 2006-07 Season (Site-2)

140 Apparent N loss = A – B = -6 lb-N/ac 120 Plant N uptake 100 Soil inorganic N (0’-1’ depth)

80 A 60

40 Precip. 20 mm B 0 20 wks from the transplanting

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Sudan grass

Season Biomass Biomass N % C/N Site d.w. t/ac lb-N/ac

2005-06 3.6 2.3 166 17 (Site-1)

2006-07 4.7 1.4 132 31 (Site-2)

2005 2006 (Site-1) (Site-2)

Experimental Design

Season Main plots Split plots Site (In-season N*) (Pre-plant N) 2007-08 0, 150, 300 lb-N/ac Compost 5 t/ac (CP) Site-3** with liquid organic fertilizer CP + Blood meal 75 lb-N/ac (CP+BM75) 2008-09 CP + Blood meal150lb-N/ac (CP+BM150) Site-4**

* Biweekly applications through Mar. to Oct. ** Managed by a large scale specialized grower

Grower’s standard practice.

Marketable Fruit Yield (Mean ± SEM)

Mkt: ANOVA (P≤0.05) Mkt: ANOVA (P≤0.05) In-season: * 0 150 300 2007-08 (Site-3) In-season: n.s. Pre-plant:** CP +BP75 +BP150 2008-09 (Site-4) Pre-plant: n.s. In-season x Pre-plant: n.s. In-season x Pre-plant: n.s.

40,000 40,000

30,000 30,000

20,000 20,000

Marketable fruit yield lb/acyieldfruit Marketable Marketable fruit yield lb/acyieldfruit Marketable

10,000 10,000

0 0

CP CP CP

CP CP

Pre-plant CP Pre-plant

CP+BM75 CP+BM75 CP+BM75

CP+BM75 CP+BM75 CP+BM75

CP+BM150 CP+BM150 CP+BM150

CP+BM150 CP+BM150 CP+BM150 In-season 0 lb-N/ac 150 lb-N/ac 300 lb-N/ac In-season 0 lb-N/ac 150 lb-N/ac 300 lb-N/ac

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Marketable Fruit Yield (Mean ± SEM)

Mkt: ANOVA (P≤0.05) Cull: ANOVA (P≤0.05) In-season: * 0 150 300 2007-08 (Site-3) In-season: * 0 150 300 2008-09 (Site-4) Pre-plant: n.s. Pre-plant: n.s. In-season x Pre-plant: n.s. In-season x Pre-plant: n.s.

70

40,000 40,000 60

50

30,000 30,000 Cull Cull rate % 40

20,000 20,000

Marketable fruit yield lb/acyieldfruit Marketable 30 Marketable fruit yield lb/acyieldfruit Marketable

20 10,000 10,000

10

0 0 0

CP CP CP

CP CP

Pre-plant Pre-plant CP

CP+BM75 CP+BM75 CP+BM75

CP+BM75 CP+BM75 CP+BM75

CP+BM150 CP+BM150 CP+BM150

CP+BM150 CP+BM150 CP+BM150 In-season 0 lb-N/ac 150 lb-N/ac 300 lb-N/ac In-season 0 lb-N/ac 150 lb-N/ac 300 lb-N/ac

N loss and Winter Weather (Nov. 1 – Jan. 31. Watsonville, CA)

Mean Season Precip. Mean Max. Mean Min. N loss Site inch Air Temp ºF Air Temp. ºF lb-N/ac

2005-06 110 (Site-1) 15.2 (+3.5)* 64.2 (+1.4) 42.8 (+2.3)

2006-07 -24 (Site-2) 6.6 (-5.1) 62.8 (±0) 38.8 (-1.6)

2007-08 17 (Site-3) 10.7 (-0.9) 61.5 (-1.1) 39.6 (-0.9)

2008-09 29 (Site-4) 6.1 (-5.6) 64.9 (+2.2) 41.0 (+0.5)

* Difference from the 30 yr mean (1979-2008).

Discussion Pre-plant Compost (seasons 1-2) • No significant effect in yield and soil/plant N dynamics in a short term Sudan grass cover crop (seasons 1-2) • Low C/N (17): quick N release and large N loss (as broccoli residues) • High C/N (31): no early N release but no effect on yield in a short term Blood meal (seasons 3-4) • Effective only in a dry-warm winter year (as it works in the Southern district)

In-season N No responses in 3 out of 4 seasons • Partially due to low distribution efficiency? • 300 lb-N/ac: increased marketable yield in one season (low overall yield) but increased cull rate in another season (high overall yield)

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Limiting winter N losses in the Northern region

Based on analysis of 6 field trials with 53 treatment combinations, we have found that N loss is strongly dependent upon: • Residual soil nitrate from previous crop • Amount of N added in crop residue immediately before strawberries • Amount of pre-plant organic fertilizer (e.g. pelleted organic fertilizer, blood meal) added

Rule of thumb: to keep N losses below 50 lb-N/ac, don’t add any pre-plant organic fertilizer if

1. Residual NO3-N is above ~25 mg/kg in 0’-1’ soil depth 2. Broccoli residues* were incorporated before planting strawberries * normally provides 150 lb-N/ac

SUMMARY - N Management in Organic Strawberries

• N demand by strawberries varies depending on the region and the fruit yield • In the Southern (warmer) region, N uptake increases faster than the Northern (colder) regions • Pre-plant N • more effective in the south than the north • can increase fruit yield in dry-warm winters in the north

• Total N uptake by strawberries can vary from 90 to 175 lb-N/ac depending on the yield

SUMMARY - N Management in Organic Strawberries (Continued)

• Mineralized N from a crop residue, organic fertilizers and SOM does not match the long and steady N needs of strawberries • In-season N applications necessary • Mineralized N from crop residues and residual soil nitrate • Major sources of excess N in fall and vulnerable to loss during rainy winter in the north • A guideline to limit N loss

• Fertigation of liquid organic fertilizer • common practice as the in-season N application but has some efficiency issues to be addressed • low yield of organic strawberries may partially be due to the low N supply during the harvest season?

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FUTURE STUDIES - N Management in Organic Strawberries

• Improving fertigation efficiency in organic strawberries • Effect of filter mesh size, high pressure agitation in a mixing chamber prior to injection, organic wetting agent/dispersant

• Reducing N loss during rainy winter • N loss estimation tool based on regression analysis • Immobilizing residual soil inorganic N by high C/N amendments

• Interaction between plant (root) health and N demand • Low yield of organic strawberries due to pathogen infection, N deficiency, or both? • N management under anaerobic soil disinfestation

References

• Muramoto, J., and Gaskell, M. 2012. Nitrogen management for organic strawberries, p. 43-53, In S. T. Koike, et al., eds. Organic strawberry production manual. The University of California Division of Agricultural & Natural Resources, Richmond, CA.

• Netafim, 2011. Organic Nutrients, In Guidelines for irrigation systems maintenance. http://www.netafimusa.com /files/literature/agriculture/other- literature/crop-applications/Preventive- Maintenance-Guide.pdf

Acknowledgements

• Funding: USDA-Organic Research and Extension Initiative 2004-51300- 02232 and 2011-51300-30677 • Manzanita Farms, Santa Maria, CA • San Luis Obispo and Santa Barbara counties, CA • High Ground Organics, Watsonville, CA • Reiter Affiliated Companies, Watsonville, CA • Driscoll’s Strawberry Associates, Watsonville, CA • Cypress Consulting, Corralitos, CA • Staff, students, and volunteers of the Shennan lab and the Gliessman lab, UCSC

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Questions?

Joji Muramoto [email protected] Mark Gaskell: [email protected] Carol Shennan [email protected]

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