Nitrogen Fertility Management in Nitrogen Fertility Management in Organic ProductionOrganic Production

Richard Smith, Farm AdvisorRichard Smith, Farm AdvisorMonterey, Santa Cruz and San Benito CountiesMonterey, Santa Cruz and San Benito Counties

Characteristics of the Organic Characteristics of the Organic Production SystemProduction System

• Nearly all N is provided by organic sources• Mineralization needs to occur to produce

nitrate and ammonium for plant growth• There is a need to build up levels of soil

organic matter which is used as source of N for crop growth

• Cover crops, crop residues and fertilizers also contribute N for crop growth

Plants Microbes

CEC

Death Death

Nitrogen CycleNitrogen Cycle Crop residue, Compost, FertilizersSoil Organic MatterSoil Organic Matter

Most soil N is in this formMost soil N is in this form(1000 (1000 –– 3000 lbs N/A)3000 lbs N/A)

Mineralization*Mineralization*

Nitrification

NH4+

NO3-

* Mineralization is a key step in making N available for plant g* Mineralization is a key step in making N available for plant growth rowth It is dependent upon adequate soil temperatures (i.e. > 50 F)It is dependent upon adequate soil temperatures (i.e. > 50 F)

Sources of Nitrogen for Crop GrowthSources of Nitrogen for Crop Growth1.1. Residual mineral N (NOResidual mineral N (NO33 --N and NHN and NH44 --N)N)2.2. In season mineralization of N from soil In season mineralization of N from soil

organic matter organic matter 3.3. N availability from prior crops & cover N availability from prior crops & cover

crops crops 4.4. Organic FertilizerOrganic Fertilizer

1.1. Residual Soil Mineral N Residual Soil Mineral N (nitrate and ammonium pool)(nitrate and ammonium pool)

•• Can be measured with the Presidedress Can be measured with the Presidedress Nitrate Quick TestNitrate Quick Test

Presidedress Nitrate Quick TestPresidedress Nitrate Quick Test

Residual Soil Mineral N Residual Soil Mineral N •• Nitrate is typically low in organic Nitrate is typically low in organic

production systemsproduction systems• Organic systems differ from

conventional systems in that N management cannot typically be based on measuring a large pool of mineral N in the soil

• This can vary however, depending upon fertilization practices

0

10

20

30

40

50

60

70

80

May May Jun Jun Jul Jul Jul Aug

Conventional

Organic

Comparison of Organic and Conventional OnionsComparison of Organic and Conventional OnionsHollister, 1996Hollister, 1996

Soi

l ppm

NO

3-N

Soil Nitrate in Organic VegetableSoil Nitrate in Organic Vegetable Production 2001 Production 2001 -- 20032003

0

5

10

15

20

25

Summer-

Yr1Fall

-Yr1

Wint

er-Yr1

Spring

-Yr1

Summer-

Yr2Fall

-Yr2

Wint

er-Yr2

Spring

-Yr2

Summer-

Yr3Fall

-Yr3

Wint

er-Yr3

NO

3-N

µg

g-1 d

ry s

oil

0-15 cm

15-30 cm

Jackson, 2005Jackson, 2005

2. In season mineralization of N from 2. In season mineralization of N from soil organic mattersoil organic matter

•• 2 to 5 % of soil organic matter 2 to 5 % of soil organic matter decomposes annually decomposes annually

•• As the organic matter decomposes As the organic matter decomposes NH4NH4++ and nitrate NO3and nitrate NO3-- are releasedare released

In season mineralization of N from In season mineralization of N from soil organic mattersoil organic matter

•• A rough estimate of mineralization from soil A rough estimate of mineralization from soil organic matter can be made based on the organic matter can be made based on the amount of organic N present in the soil and amount of organic N present in the soil and the percent of that N likely to mineralize over the percent of that N likely to mineralize over a given period of time. a given period of time.

In season mineralization of N from In season mineralization of N from soil organic mattersoil organic matter

For a soil with 1% organic matter:For a soil with 1% organic matter:•• 2,800 lb organic N / acre x 0.02 (percent of 2,800 lb organic N / acre x 0.02 (percent of

organic N that mineralizes in 60 days) = organic N that mineralizes in 60 days) =

56 lb plant available N / acre 56 lb plant available N / acre over two monthsover two months

Nitrogen Release Characteristics Nitrogen Release Characteristics of N Soil Organic Matterof N Soil Organic Matter

Relative Rate of N Mineralization

Ava

ilabl

e N

itrat

e (p

pm)

5

10

15

20

Soil organic matter mineralization

3. N availability from cover crops3. N availability from cover crops

•• Cover crops typically take up or fix between 100Cover crops typically take up or fix between 100-- 200 lbs N/ acre 200 lbs N/ acre

•• Cover crops are often tilled into the soil when the Cover crops are often tilled into the soil when the C:N ratio <20 to achieve a net release of N to the C:N ratio <20 to achieve a net release of N to the soil to feed subsequent vegetable cropssoil to feed subsequent vegetable crops

•• Cover crops with a low N content such as mature Cover crops with a low N content such as mature cereals (i.e. C:N ratio > 20) temporarily tie up cereals (i.e. C:N ratio > 20) temporarily tie up nitrogen* nitrogen*

* soil microbes utilize available soil N to * soil microbes utilize available soil N to break down the cover crop residuebreak down the cover crop residue

Nitrogen release from cover crop Nitrogen release from cover crop residue based on the N contentresidue based on the N content

Nitrogen ReleaseNitrogen ReleasePercent N Percent N

in Cover Cropin Cover CropExamples of Cover CropsExamples of Cover Crops

Will Tie up NWill Tie up N 0.50.5 Cereal StrawCereal Straw

Will Tie up NWill Tie up N 1.01.0 Cereal StrawCereal Straw

Will Tie up NWill Tie up N 1.51.5 Cereal at headingCereal at heading

May Tie up N*May Tie up N* 2.02.0 Cereal pre headingCereal pre heading

May Tie up N*May Tie up N* 2.52.5 Mustards at heading and Mustards at heading and ImmImm. cereal . cereal

Will Release NWill Release N 3.03.0 Mustards, legumes and juvenile cerealMustards, legumes and juvenile cereal

Will Release NWill Release N 3.53.5 Legumes and immature mustardsLegumes and immature mustards

Will Release NWill Release N 4.04.0 LegumesLegumes

Cover CropCover CropProteinsProteins

MicrobesMicrobes

AvailableAvailableMineralMineral

NitrogenNitrogen

MicrobesMicrobes

Depends uponDepends uponC:N; lignin and C:N; lignin and PolyphenolsPolyphenols

Typically <10Typically <10--30% of cover crop 30% of cover crop N is taken up by the first subsequent N is taken up by the first subsequent

Crop*Crop*

* A good deal of cover crop N remains in the system and can* A good deal of cover crop N remains in the system and cancan be taken up in later years (i.e. 73%)can be taken up in later years (i.e. 73%)

N availability from cover cropsN availability from cover crops

•• The rate of mineralization of available N from The rate of mineralization of available N from a low C:N (<20) cover crop increases over a a low C:N (<20) cover crop increases over a threethree-- to sixto six--week period following week period following incorporationincorporation

•• Soil N levels return to preSoil N levels return to pre--incorporation incorporation levels by week 6levels by week 6--1010

N Release Pattern from Cover CropsN Release Pattern from Cover Crops

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2

4

6

8

10

12

14

16

18

0 11 25 39 53 67Days After Incorporation of Cover Crop

Tota

l Min

eral

Nitr

ogen

(ppm

)

Legume MixMustardOats

Smith & Brennan, 2003Smith & Brennan, 2003

Nitrogen Release Characteristics Nitrogen Release Characteristics of N From Cover Cropof N From Cover Crop

Relative Rate of N Mineralization

Ava

ilabl

e N

itrat

e (p

pm)

Cover Crop Mineralization

Cover Crop Incorporation

5

10

15

20

Soil organic matter mineralization

4. N Availability from 4. N Availability from Organic FertilizersOrganic Fertilizers

MaterialMaterial NitrogenNitrogen MaterialMaterial NitrogenNitrogenChilean nitrateChilean nitrate 1616 Soybean mealSoybean meal 77Blood mealBlood meal 1212 Processed liquid Processed liquid

fishfish44

Feather mealFeather meal 1212 Alfalfa mealAlfalfa meal 44Seabird and bat Seabird and bat guanoguano

99--1212 Pelleted chicken Pelleted chicken manuremanure

22--44

Fish meal or powderFish meal or powder 1010--1111 Bone MealBone Meal 22Meat and bone mealMeat and bone meal 88 KelpKelp <1<1

Pelleted Poultry ManurePelleted Poultry Manure Net N Mineralization Net N Mineralization

05

1015

202530

3540

1 Week 4 Weeks 8 Weeks

5977

Incubation Incubation -- WeeksWeeksHartz and Johnstone, 2006Hartz and Johnstone, 2006

Fish PowderFish Powder Net N Mineralization Net N Mineralization

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10

20

30

40

50

60

70

1 Week 4 Weeks 8 Weeks

5977

Incubation Incubation -- WeeksWeeksHartz and Johnstone, 2006Hartz and Johnstone, 2006

Feather MealFeather Meal Net N Mineralization Net N Mineralization

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10

20

30

40

50

60

70

1 Week 4 Weeks 8 Weeks

5977

Incubation Incubation -- WeeksWeeksHartz and Johnstone, 2006Hartz and Johnstone, 2006

Percent of Initial Organic N Percent of Initial Organic N Mineralized Mineralized –– 4 Weeks Incubation4 Weeks Incubation

0

10

20

30

40

50

60

70

pelletedpoultry

sea birdguano

fish powder feather meal

5977

Hartz and Johnstone, 2006Hartz and Johnstone, 2006

Nitrogen Release Characteristics Nitrogen Release Characteristics of N From Fertilizerof N From Fertilizer

Relative Rate of N Mineralization

Ava

ilabl

e N

itrat

e (p

pm)

FertilizerMineralization

5

10

15

20

Soil organic matter mineralization

Integrating Sources of N for Integrating Sources of N for Organic ProductionOrganic Production

2006 Cover Crop x Fertilizer Trial2006 Cover Crop x Fertilizer Trial

•• The cover crop plots produced 3.2 The cover crop plots produced 3.2 tons of biomass and contained 194.5 lbs N/A tons of biomass and contained 194.5 lbs N/A

•• The cover crop was incorporated February 14The cover crop was incorporated February 1412 inches of rain fell between incorporation 12 inches of rain fell between incorporation of the cover crop and transplanting broccoli of the cover crop and transplanting broccoli on April 20on April 20

Rain Events Between Cover Crop Rain Events Between Cover Crop Incorporation and Transplanting BroccoliIncorporation and Transplanting Broccoli

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

14-Feb 21-Feb 28-Feb 7-Mar 14-Mar 21-Mar 28-Mar 4-Apr 11-Apr 18-Apr

Rai

nfal

l (in

.)

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12

14

Cum

ulat

ive

Rai

nfal

l (in

.)

Rainfall EventsCum. Rainfall

Soil Temperatures Between Cover Crop Soil Temperatures Between Cover Crop Incorporation and Transplanting BroccoliIncorporation and Transplanting Broccoli

30

35

40

45

50

55

60

65

14-Feb 21-Feb 28-Feb 7-Mar 14-Mar 21-Mar 28-Mar 4-Apr 11-Apr 18-Apr

Soil

Tem

pera

ture

(deg

rees

F)

Total Mineral Nitrogen in Soil Between Total Mineral Nitrogen in Soil Between Cover Crop Incorporation and Cover Crop Incorporation and

Transplanting BroccoliTransplanting BroccoliTotal Mineral Nitrogen, Hartnell Organic Plot 2006

0.0

2.0

4.0

6.0

8.0

10.0

12.0

21-Feb 1-Mar 9-Mar 16-Mar 23-Mar 31-Mar 6-Apr 13-Apr 20-Apr

Tota

l Min

eral

N (m

g/kg

+/-

SEM

)

CC No CC

Harvest Harvest –– Number of HeadsNumber of Heads Number/ANumber/A

05000

100001500020000250003000035000400004500050000

0 75 150 225

No Cover CropCover Crop

Pounds N/APounds N/A

Harvest Harvest –– Weight of HeadsWeight of Heads Tons/ATons/A

012345678

0 75 150 225

No Cover CropCover Crop

Pounds N/APounds N/A

N availability from cover cropsN availability from cover crops

•• It is likely that a substantial portion of the nitrogen It is likely that a substantial portion of the nitrogen contained in the cover crop was lost to leaching contained in the cover crop was lost to leaching prior to planting the broccoli prior to planting the broccoli

•• In spite of these conditions, there was an increase In spite of these conditions, there was an increase of 25 lbs of N/A in the biomass of broccoli in cover of 25 lbs of N/A in the biomass of broccoli in cover cropped plots vs noncropped plots vs non--cover cropped plots at the cover cropped plots at the end of the growing season.end of the growing season.

•• Mark Gaskell has typically seen cover crops to Mark Gaskell has typically seen cover crops to contribute 100 lbs of N/A in studies on peppers and contribute 100 lbs of N/A in studies on peppers and cabbagecabbage

High Yielding Treatments Low High Yielding Treatments Low Synchrony form Cover Crop but Good Synchrony form Cover Crop but Good Synchrony of N Release from FertilizerSynchrony of N Release from Fertilizer

Relative Rate of N Mineralization

Ava

ilabl

e N

itrat

e (p

pm)

Crop Demand

Cover Crop Mineralization

Cover Crop Incorporation

FertilizerMineralization

5

10

15

20

Soil organic matter mineralization

Low Yielding Treatments had Poor Synchrony Low Yielding Treatments had Poor Synchrony between N Availability from Cover Crop and between N Availability from Cover Crop and

Fertilizer Rates that were too LowFertilizer Rates that were too Low

Relative Rate of N Mineralization

Ava

ilabl

e N

itrat

e (p

pm)

Crop Demand

Cover Crop Mineralization

Cover Crop Incorporation

FertilizerMineralization

5

10

15

20

Soil organic matter mineralization

Organic Fertilizer Form and Timing TrialOrganic Fertilizer Form and Timing Trial Watsonville, 2001Watsonville, 2001

TreatmentTreatment PreplantPreplantMay 8May 8

Top Top dressdress

May 31May 31

Top Top dressdressJune 7June 7

Top Top dressdress

June 14June 14

TotalTotal

UntreatedUntreated 00 00 00 00 00Fert Treat No. 1Fert Treat No. 1 4545 4545 4545 4545 180180Fert Treat No. 2Fert Treat No. 2 9090 00 4545 4545 180180Fert Treat No. 3Fert Treat No. 3 135135 00 00 4545 180180

1) Meat Meal 81) Meat Meal 8--55--1; 2) Feather Meal 121; 2) Feather Meal 12--00--003) Blood Meal 133) Blood Meal 13--00--0; 4) Guano/Chicken 70; 4) Guano/Chicken 7--00--00

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50

1 2 3 4 5 6 7

Guano/Chicken

Blood

NitrateNitrate--Nitrogen in the Soil of 135Nitrogen in the Soil of 135--45 45 Fertilizer TreatmentsFertilizer Treatments

Organic Broccoli, Watsonville, 2001Organic Broccoli, Watsonville, 2001

Fertilizer Application

0

50

100

150

200

1 2 3 4 5Untreated Meat Feather Blood Guano/

Meal Meal Meal Chicken

Total Number of Heads, Organic BroccoliTotal Number of Heads, Organic BroccoliWatsonville, 2001Watsonville, 2001

Total Weight of Heads, Organic BroccoliTotal Weight of Heads, Organic BroccoliWatsonville, 2001Watsonville, 2001

0

1020

30

4050

60

1 2 3 4 5Untreated Meat Feather Blood Guano/Meal Meal Meal Chicken

010203040506070

1 2 3 4 5 6--------------Blood MealBlood Meal-------------------- ------------Guano/ChickenGuano/Chicken------------

45 9045 90--45 135 45 9045 135 45 90--45 13545 1354x 2x 4x 4x 2x 4x 2x2x

Comparison of Materials and TimingComparison of Materials and TimingOrganic Broccoli, Watsonville, 2001Organic Broccoli, Watsonville, 2001

Wei

ght (

lbs)

Chicken/Guano Rate and Timing in Chicken/Guano Rate and Timing in Good Synchrony with Crop DemandGood Synchrony with Crop Demand

0 8

Weeks

Nitr

ate

Con

cent

ratio

n

Crop Demand

Fertilizer N Availability

Background NitrateAvailability without Cover Crop

Fertilizers Rate is Adequate, but Timing and Fertilizers Rate is Adequate, but Timing and Mineralization Rate Out of Synch with Crop Mineralization Rate Out of Synch with Crop

Demand (i.e. 4x rate of 45 lbs N/A)Demand (i.e. 4x rate of 45 lbs N/A)

0 8

Weeks

Nitr

ate

Con

cent

ratio

n

Crop Demand

Fertilizer N Availability

Background NitrateAvailability without Cover Crop

Fertilizers Rate is Adequate, but Timing is Out Fertilizers Rate is Adequate, but Timing is Out of Synch with Crop Demandof Synch with Crop Demand

(i.e. 4x rate of 45 lbs N/A)(i.e. 4x rate of 45 lbs N/A)

0 8

Weeks

Nitr

ate

Con

cent

ratio

n

Crop Demand

Fertilizer mineral N

Background Mineral NAvailability without Cover Crop

Integrating All Sources of NitrogenIntegrating All Sources of Nitrogen

•• Achieving effective synchrony between Achieving effective synchrony between crop uptake and N supplied by crop uptake and N supplied by mineralization from soil organic matter, mineralization from soil organic matter, cover crop residues and fertilizers is the cover crop residues and fertilizers is the challenge for managing N fertility of challenge for managing N fertility of vegetables in organic systemsvegetables in organic systems

Effective Synchrony Between Effective Synchrony Between Mineralization from the Various Mineralization from the Various

Sources and Crop DemandSources and Crop Demand

Relative Rate of N Mineralization

Ava

ilabl

e N

itrat

e (p

pm)

Crop Demand

Cover Crop Mineralization

Cover Crop Incorporation

FertilizerMineralization

5

10

15

20

Soil organic matter mineralization

SummarySummary

•• Nitrogen fertilization in organic systems is Nitrogen fertilization in organic systems is trickier than in conventional systems where trickier than in conventional systems where applications of readily available N can be applications of readily available N can be applied in a timely mannerapplied in a timely manner

•• There are typically large pools of organic N in There are typically large pools of organic N in soils, but the availability of this N and the soils, but the availability of this N and the synchrony of release and availability for crop synchrony of release and availability for crop production are difficult to predictproduction are difficult to predict

SummarySummary

•• As a result, organic growers have to develop As a result, organic growers have to develop excellent skills and knowledge to work with excellent skills and knowledge to work with this systemthis system

•• There may be a tendency to over fertilize, There may be a tendency to over fertilize, especially in cold soils to make sure there is especially in cold soils to make sure there is adequate material available for mineralizationadequate material available for mineralization