Impact of Cover Crops on Nutrient and Sediment Loss from Vegetable Production

Fields

Richard Smith and Michael CahnUniversity of California Cooperative ExtensionMonterey County

Salinas Valley Vegetable Production System

Intensive production areaIntensive production areaMost land is double-cropped High land rents and early planting High land rents and early planting

schedules necessitates keeping ground fallow over the winter toground fallow over the winter to facilitate spring planting schedules

First plantings of lettuce occur in December/JanuaryDecember/January A cover crop can potentially

di t l l ti tidisrupt early planting operations As a result, <5% of vegetable

ground is cover cropped

Cover crops are a key tool: Improve soil qualityReduce erosion and sediment loss Trap nitrate and prevent its loss to

under ground aquifers during winter t tstorm events

Help improve water infiltrationD il t f th iDry soil out for the spring

Given the constraints to their use: We examined the use of low residue

cover crops as an alternative cover crop system to over come some of the limitations to the use of coverthe limitations to the use of cover cropsWhat can this practice do for growerWhat can this practice do for grower

to help deal with water quality issues Is it economically feasible?Is it economically feasible?

Low residue cover crops: Th l t d i t b d They are planted on winter beds and allowed to grown for 50-60 d th kill d ith h bi iddays then killed with an herbicide (mechanically??) The residue is allowed to

decompose, and under ideal conditions, the ground is ready to plant with normal tillage

Trials Over the Past Three Winters

• Winter dormant triticale planted in pfurrow only• Cereal rye broadcast on beds andCereal rye broadcast on beds and furrows

• Cover crops were killed with l h t t i t l 55glyphosate at approximately 55

days after germination to manageable biomass accumulation

2009-2010 Trial

8 40-inch beds wide x 1100 ft long; 7 furrow bottoms tied together and passed g pthrough a flue where quantity was measured and samples collected forsamples collected for nutrient and sediment loads December 14

January 7 February 4

Triticale 888Triticale 888 Triticale 888

AGS 104 Rye AGS 104 Rye

Nitrogen and Low Residue Cover Crops

• Low residue coverLow residue cover crops do not sequester as much nitrogen as full‐term cover crops

• They also begin to “leak” the nitrogen quickly after killing

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105,804 gal/acre2.3% of rainfall

Cover Crop Treatment

Rye Triticale Bare

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1200

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800

1000

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600

800

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73 lbs/acre

Cover Crop Treatment

Rye Triticale Bare

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3000

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2000

2500

3000 BareTriticaleRye

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Jan 2

Feb 0

Feb 0

Feb 1

Feb 2

Mar 0

Mar 0

Nutrient Loss in Surface Water from Cover Crop Treatmentsfrom Cover Crop Treatments

Treatment Total N Ammonium-N Nitrate-N Soluble-P Total P K --------------------------- lbs/acre -------------------------------

Rye 0.21 0.05 0.04 0.17 0.20 0.80Triticale 0.60 0.05 0.03 0.24 0.47 1.30Control 4 78 0 12 0 49 1 06 3 71 4 12Control 4.78 0.12 0.49 1.06 3.71 4.12

------------ % reduction in loss compared to control ------------------Rye 96 59 92 84 95 81Triticale 87 58 93 78 87 69

Leached Ions in Cover Crop /Treatments (lbs/A)

Treatment Potassium Calcium Magnesium Sodium Chloride Sulfate NitrateTreatment Potassium Calcium Magnesium Sodium Chloride Sulfate Nitrate

Bare fallow 9 133 32 88 158 36 699 133 32 88 158 36 69Low residue Triticale Trios 102

18 216 55 178 275 60 110Low residue 16 226 63 191 289 69 111Rye AGS 104

16 226 63 191 289 69 111

Leached Ions in Cover Crop /Treatments (lbs/A)

Treatment Potassium Calcium Magnesium Sodium Chloride Sulfate NitrateTreatment Potassium Calcium Magnesium Sodium Chloride Sulfate Nitrate

Bare fallow 9 133 32 88 158 36 699 133 32 88 158 36 69Low residue Triticale Trios 102

18 216 55 178 275 60 110Low residue 16 226 63 191 289 69 111Rye AGS 104

16 226 63 191 289 69 111

Nitrate Leaching from Full-term and Low-residue Cover Crops

BareFull Term Low-residue

Full Term

Lysimeter Maintained at 20 Kp

Nitrogen in Cover Crop Biomass/pounds/A

120

140

160

Full

80

100

120

lbs N

/A Low

40

60

0

20

5‐Jan 19‐Jan 28‐Jan 10‐Feb 23‐Feb 9‐Mar

Low Residue Cover Crop Have Minimal Effect on Nitrate Leaching

120

140

N/h

a 80

100Bare Low Full Full term cover

crop reduce nitrate leaching

All cover cropallow leaching

kg N

20

40

60Low sprayed

nitrate leachingloss by about

70 lbs/A

when small

11/29 12/13 12/27 1/10 1/24 2/7 2/21 3/7 0

20

Date

Problems Encountered on 80‐inch Beds in 2010 – 2011 Trial

• Adjacent strawberryAdjacent strawberry field

• Needed to use a grass gselective herbicide, but it killed the cover crop very slowly 

• Did not kill broadleaf d h h lweeds which later 

became problemsD th d d• Dry weather reduced residue decomposition

Problems Encountered on 80‐inch Beds in 2011

• As a result, the trialAs a result, the trial was terminated early in order for the grower to be able to prepare the beds and stay on his l ti h d lplanting schedule

• This was an important lesson on what can golesson on what can go wrong

Ways to Resolve the ProblemsWays to Resolve the Problems• 40‐inch beds should be the focus of thisthe focus of this practice

• If planting on 80‐inchIf planting on 80 inch beds, just plant the furrow bottom

• Do not plant seed too deep

• Aggressively manage weeds

• Kill cover crop on time

CostsCostsTreatment Seed

costCultivation for weed

Glyphosate @ 1

Glyphosate application

Total Cost/Acost for weed

control2@ 1

gallon/Aapplication

$/ACost/A

Bare 0.0 17.0 0.0 0.0 17.0Triticale ‘888’ 41.0 0.0 40.0 20.0 101.0Rye ‘AG104’ 44.1 0.0 40.0 20.0 104.1

Conclusions and Recommendationsd bl f l• Low residue cover crops are able to significantly 

reduce surface water runoff, sediment  and nutrient loss during in surface water during winter stormloss during in surface water during winter storm events

• Target this technique to soils with high runoff andTarget this technique to soils with high runoff and sediment loss potential (e.g. eastside of the Salinas Valley)y)

• They greatly increased water infiltration into the soil, thereby providing a cultural practice that can increase ground water recharge and move accumulated salts out of the soil profile

• Establish as early as possible to provide protection from early rains

Conclusions and Recommendations• They must be killed before they produce too much biomass that would disrupt subsequent planting operations – keep in mind that once killed they still provide effective sediment loss reduction and increased infiltration for a good amount of time

• They are only able to accumulate moderate amounts of nitrate from the soil and may not yreduce nitrate leaching in storms later in the cover crop growth cyclep g y

Conclusions and Recommendations• Planting cover crops just in the furrow bottom may be the safest approach to using these cover crops so th t th d t di t b t t blthat they do not disrupt subsequent vegetable planting operations (especially true on 80 inch beds)

• Furrow bottom plantings on 40 inch beds occupy• Furrow bottom plantings on 40 inch beds occupy about 1/3 of the area of the field, and you can calculate your seeding rate accordinglycalculate your seeding rate accordingly

• However, given the difficulties of planting the furrow, it is advisable to a higher seeding rate to get an g g gadequate plant population and early ground cover

Acknowledgementsg

• Monterey Community Foundationy y• California Department of Food and

Agriculture, Fertilizer Research andAgriculture, Fertilizer Research and Education Program

• D’Arrigo Brothers and Sea Mist Farms• D Arrigo Brothers and Sea Mist Farms

Go to YouTube and type in “Cover Crops Salinas”