Cover Crop Contributions to Nitrogen Fertilityvric.ucdavis.edu/events/2009_osfm_symposium/UC Organic...
Transcript of Cover Crop Contributions to Nitrogen Fertilityvric.ucdavis.edu/events/2009_osfm_symposium/UC Organic...
Cover Crop Contributions to Cover Crop Contributions to Nitrogen FertilityNitrogen Fertility
Richard SmithRichard SmithVegetable Crop and Weed Science Farm AdvisorVegetable Crop and Weed Science Farm AdvisorUniversity of California Cooperative Extension University of California Cooperative Extension Monterey CountyMonterey County
Cover Crops: BackgroundCover Crops: Background•• Cover crops are an important agricultural Cover crops are an important agricultural
production practiceproduction practice•• In modern agriculture their use is In modern agriculture their use is
common in permanent crops but is more common in permanent crops but is more problematic in annual cropsproblematic in annual crops
•• They are mostly grown in the winter, but They are mostly grown in the winter, but can can ““get in the wayget in the way”” of preparing the of preparing the ground for early spring planting if wet ground for early spring planting if wet weather prevents soil incorporationweather prevents soil incorporation
Cover Crops: BackgroundCover Crops: Background•• Cover crops can be a source of nitrogen Cover crops can be a source of nitrogen
for subsequent cash cropsfor subsequent cash crops•• However, regarding N availability, there However, regarding N availability, there
are important agronomic details that need are important agronomic details that need to be discussed to better understand the to be discussed to better understand the role that cover crops can play in providing role that cover crops can play in providing nitrogen to subsequent cropsnitrogen to subsequent crops
Legumes: Fix N from the air and provide a net input of N to the soil
Cereals, Mustards, Others: Scavenge & recycle residual N from soil
Sweet CloverSweet Clover
OatsOats
Legume have the ability to obtainthe N they need by N fixation
Low Nitrogen Scenario: Oat are N Stressed (yellowed)
Legumes can leak some of their nitrogento plants growing in their immediate vicinity
Compare the color of these two oat plants
Legume and cereal mixestake advantage of the N fixing ability of
legumes and the N scavenging ability of cereals
How Much N do Cover CropsHow Much N do Cover Crops Contain?Contain?
Nitrogen Content of Cover CropsNitrogen Content of Cover Crops Organic Farm in San Benito County Organic Farm in San Benito County –– moderate Nmoderate N
Six year AverageSix year Average
Cover CropCover Crop Lbs N/ALbs N/A
CerealsCereals 131.5131.5
LegumesLegumes 145.7*145.7*
Cereal/Legume MixCereal/Legume Mix 177.1177.1
* How much is net fixation is not known
Cover CropsCover CropsBiomass Biomass
T/AT/A% N% N
in Topsin Topslbs N/acrelbs N/acre
in Topsin Tops
White MustardWhite Mustard 2.52.5 3.93.9 194.8194.8Indian MustardIndian Mustard 2.22.2 4.54.5 199.7199.7Cereal Rye Cereal Rye 3.13.1 3.33.3 203.7203.7
Scavenging of Nitrogen by Cover CropsScavenging of Nitrogen by Cover CropsFollowing Conventional Lettuce Production Following Conventional Lettuce Production –– high Nhigh N
Chualar, 2003Chualar, 2003
What rate is the nitrogen contained What rate is the nitrogen contained in cover crops made available to in cover crops made available to
the subsequent cash crop?the subsequent cash crop?
•• The release of nitrogen by cover The release of nitrogen by cover crops is dependent on soil moisture crops is dependent on soil moisture and temperatureand temperature
•• The nitrogen concentration of the The nitrogen concentration of the cover crop is importantcover crop is important
N Release Pattern from Cover CropsN Release Pattern from Cover Crops
0
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
Percent of Cover Crop Nitrogen Percent of Cover Crop Nitrogen Mineralized at 8 WeeksMineralized at 8 Weeks
Various legume, and non-legume, cover crops, Hartz, unpublished
Perc
ent C
over
Cro
p N
Min
eral
ized
Nitrogen Content of Cover Crop - Percent
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 Imm. cereal Mustards at heading and Imm. 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
Cereal Residue Legume ResidueCereal Residue Legume ResidueHigh C:NHigh C:N Lower C:NLower C:N
Cover CropCover CropProteinsProteins
MicrobesMicrobesNeed carbon and nitrogen for Need carbon and nitrogen for
their growththeir growth
AvailableAvailableMineralMineral
NitrogenNitrogen(Nitrate & Ammonium)(Nitrate & Ammonium)
Rate of mineralization Rate of mineralization depends mostly on depends mostly on nitrogen concentration of nitrogen concentration of the tissuethe tissue
Nitrogen Release by Cover CropsNitrogen Release by Cover Crops
•• The amount of N provided by the cover The amount of N provided by the cover crop is importantcrop is important
•• The nitrogen demand by the cash crop is The nitrogen demand by the cash crop is also important to understandalso important to understand
Biomass Accumulation and Biomass Accumulation and Nitrogen Demand of LettuceNitrogen Demand of Lettuce
•• Rapid growth from 30 to 60 days following plantingRapid growth from 30 to 60 days following planting•• High Peak Demand for NHigh Peak Demand for N
4-5 lbs Nitrogen/Acre/dayPeak Uptake Demand
Field Trial on Nitrogen Release and Field Trial on Nitrogen Release and Crop ResponseCrop Response
•• A field study conducted by Rick Miller A field study conducted by Rick Miller (1987(1987--1988), conducted on the UCD farm, 1988), conducted on the UCD farm, illustrates an optimal situation of a cover illustrates an optimal situation of a cover crop providing adequate amounts of N in crop providing adequate amounts of N in synchrony with crop demandsynchrony with crop demand
Nitrogen Content of Cover Crop TopsNitrogen Content of Cover Crop Tops Two Year Average (1987/1988)Two Year Average (1987/1988)
Miller, 1989
Nitrogen Uptake in Grain lbs/ANitrogen Uptake in Grain lbs/A Two Year Average (1987/1988)Two Year Average (1987/1988)
Miller, 1989
Grain Yield lbs/AGrain Yield lbs/A Two Year Average (1987/1988)Two Year Average (1987/1988)
Miller, 1989
Conclusions of this StudyConclusions of this Study•• The release of N from the cover crop and The release of N from the cover crop and
the uptake demand of corn synchronized the uptake demand of corn synchronized wellwell
•• This is an example of optimal use of This is an example of optimal use of nitrogen from the cover crop by the nitrogen from the cover crop by the subsequent cash cropsubsequent cash crop
2006 & 2007 Cover Crop 2006 & 2007 Cover Crop & Fertilizer Trial & Fertilizer Trial -- SalinasSalinas
Year Biomass T/A
N in TopsPercent
N in Tops lbs/A
2006 3.21 3.1 194.52007 3.71 2.1 153.4
Smith and Muramoto, 2007
2006 Soil Mineral Nitrogen2006 Soil Mineral Nitrogen Cover Crop Incorporation to Planting BroccoliCover Crop Incorporation to Planting Broccoli
2007 Soil Mineral Nitrogen2007 Soil Mineral Nitrogen Cover Crop Incorporation to Planting BroccoliCover Crop Incorporation to Planting Broccoli
2006 Nitrogen in Broccoli Biomass lbs/A2006 Nitrogen in Broccoli Biomass lbs/AAt HarvestAt Harvest
2006 Nitrogen in Broccoli Biomass lbs/A2006 Nitrogen in Broccoli Biomass lbs/AAt HarvestAt Harvest
2007 Nitrogen in Broccoli Biomass lbs/A2007 Nitrogen in Broccoli Biomass lbs/AAt HarvestAt Harvest
Broccoli Yield 2006 Trial
Broccoli Yield 2007 Trial
Summary of Cover Crop and Nitrogen Fertility Trial
When the nitrogen concentration in the cover crop was >3%, the cover crop provided the equivalent of 63 lbs of fertilizer N to the broccoli
Cover crop N boosted the yield of broccoli at all fertilization rates
Summary of Cover Crop and Nitrogen Fertility Trial
When the nitrogen concentration in the cover crop was 2%, the cover crop tied up nitrogen and it took 225 lbs of fertilizer N to over come this effect
The nitrogen concentration in the cover crop greatly affected N release to the subsequent cash crop
Composition of Cover Crop MixesComposition of Cover Crop Mixes
•• Planting Date, weather conditions and soil Planting Date, weather conditions and soil fertility can affect the composition of fertility can affect the composition of cover crop mixes and can impact their cover crop mixes and can impact their nitrogen concentration at incorporationnitrogen concentration at incorporation
Comparison of Cover Crop Comparison of Cover Crop Composition on Two Soil TypesComposition on Two Soil Types
black = cereal; gray = legumeblack = cereal; gray = legumeHollister Year 2
0
10
20
30
40
50
60
70
80
90
100 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1 < 1
84 64 32 19 81 63 254
83 63 158
15 35 68 81 18 37 75 96 17 37 85 92
H1 H2 H3 H4 H1 H2 H3 H4 H1 H2 H3 H41X 2X 3X
Seeding Rate
Abov
e G
roun
d D
ry M
atte
r (%
)
D
Brennan et al, in press
Salinas Year 2
0
10
20
30
40
50
60
70
80
90
100 18 10 < 1 9 4 < 1 4 1 < 1
59 77 84 63 65 80 83 62 73 79 72 51
23 13 16 37 25 16 17 38 23 20 28 49
H1 H2 H3 H4 H1 H2 H3 H4 H1 H2 H3 H41X 2X 3X
Seeding Rate
Abo
ve G
roun
d D
ry M
atte
r (%
)
B
Sandy loam, low fertility Clay loam, high soilSandy loam, low fertility Clay loam, high soil fertilityfertility
How Much Cover Crop N is Made How Much Cover Crop N is Made Available for Crop GrowthAvailable for Crop Growth
•• Cover crops can Cover crops can contain 100 contain 100 –– 200 200 lbs N but typically lbs N but typically less than half of less than half of this is made this is made available to the available to the subsequent cropsubsequent crop
Lettuce Soil Organic NLettuce Soil Organic NCropCrop
Jackson, 2000Jackson, 2000
Cover Crop in LettuceCover Crop in LettuceFour months after incorporationFour months after incorporation
Mineralization of Mineral Nitrogen Mineralization of Mineral Nitrogen from Cover Cropsfrom Cover Crops
•• Cover crops also play a larger role in soil Cover crops also play a larger role in soil building and provide a longbuilding and provide a long--term source term source of N that contributes to total soil nitrogen of N that contributes to total soil nitrogen content and that behaves the same as soil content and that behaves the same as soil organic matterorganic matter
Impacts of Organic Soil Building Impacts of Organic Soil Building on Nitrogen Storage in Soilon Nitrogen Storage in Soil
Soil TypeSoil Type ManagementManagement Total Soil N %Total Soil N %
Clay LoamClay Loam Organic Organic 0.170.17
Clay LoamClay Loam ConventionalConventional 0.140.14
LoamLoam Organic Organic 0.140.14
LoamLoam ConventionalConventional 0.110.11
Fine Sandy LoamFine Sandy Loam Organic Organic 0.120.12
Fine Sandy LoamFine Sandy Loam ConventionalConventional 0.060.06
Smith, 2003
Impacts of Organic Soil Building Impacts of Organic Soil Building on Nitrogen Storage in Soilon Nitrogen Storage in Soil
Soil TypeSoil Type ManagementManagement Total Soil N %Total Soil N %
Clay LoamClay Loam Organic Organic 0.170.17
Clay LoamClay Loam ConventionalConventional 0.140.14
LoamLoam Organic Organic 0.140.14
LoamLoam ConventionalConventional 0.110.11
Fine Sandy LoamFine Sandy Loam Organic Organic 0.120.12
Fine Sandy LoamFine Sandy Loam ConventionalConventional 0.060.06
Smith, 2003
Summary of Nitrogen Fertilization Summary of Nitrogen Fertilization of Organic Horticultural Cropsof Organic Horticultural Crops
•• Some crops may be able to achieve Some crops may be able to achieve economically acceptable yield from economically acceptable yield from nitrogen from cover crop decompositionnitrogen from cover crop decomposition
•• Many crops (e.g. lettuce) generally need Many crops (e.g. lettuce) generally need greater quantities of available mineral greater quantities of available mineral nitrogen to achieve economically viable nitrogen to achieve economically viable yieldsyields
Nitrogen Fertilization of Organic Nitrogen Fertilization of Organic Horticultural CropsHorticultural Crops
•• The key is for organic sources of N to The key is for organic sources of N to mineralize in sufficient quantities and mineralize in sufficient quantities and quick enough to meet crop demandquick enough to meet crop demand
•• Synchrony of supply and demandSynchrony of supply and demand
Effective Synchrony Between Effective Synchrony Between Mineralization from the Various Mineralization from the Various
Sources and Crop DemandSources and Crop Demand
Management of Cover Crops to Management of Cover Crops to Provide Nitrogen to Subsequent Provide Nitrogen to Subsequent
Cash CropsCash Crops
•• Cover crops should be incorporated in a Cover crops should be incorporated in a juvenile enough stage to prevent juvenile enough stage to prevent immobilization of N: immobilization of N:
•• Nitrogen content of the tops > 2.5%Nitrogen content of the tops > 2.5%–– Legumes at flowering or beforeLegumes at flowering or before–– Cereals well before headingCereals well before heading
Management of Cover Crops to Management of Cover Crops to Provide Nitrogen to Subsequent Provide Nitrogen to Subsequent
Cash CropsCash Crops
•• Allow sufficient time for the cover crops Allow sufficient time for the cover crops to decompose and release nitrate and to decompose and release nitrate and ammoniumammonium
•• Manage water carefully to not leach Manage water carefully to not leach available N below the root zoneavailable N below the root zone
Thank you for your attentionThank you for your attention