Soil management for organic crop production

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Soil management for organic crop production
Joel Gruver NCSU Soil Science
http//www.soil.ncsu.edu/lockers/Gruver_J/SMOCP
http//compost.tamu.edu/demos/palopinto/compost.jp
g
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Progressive sustainability
Sustainability spiral
http//www.edpsciences.org/articles/agro/pd
f/2002/07/14.pdf?accessok
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A systems approach
Host
Managing the soil food web
Adapted from Bailey and Lazarovits (2003)
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Rotations should evolve not revolve !
http//www.ncl.ac.uk/tcoa/files/breakcrops_orgagr.
pdf
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Understanding crop rotation Crop rotation is a
system of growing different types of crops in an
advantageous sequence on the same land. Well
designed crop rotations are advantageous because
of their contributions to soil fertility, soil
tilth, weed management, pest management,
disease management, enterprise diversity, labor
balance etc
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When developing a crop rotation it is useful to
consider the many crop attributes that can be
strategically varied over time
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Crop attributes Rooting depth Optimal spacing
(row width) Residue quality and
quantity Fertility requirements Ability to host
symbionts (e.g. rhizobia or mycorrhiza) Tendency
to host pests and pathogens Competitive
abilities Allelopathic impact and
sensitivity Intercropping potential Maturation
rate Disease resistance/susceptibility Climatic
adaptation Optimal timing of planting Compatabilit
y with plasticulture or other mulching systems
Economic value/marketability Tolerance of lower
fertility/acidity Ability to scavenge residual
fertility Seed bed quality required for
establishment Response to large applications of
compost/manure Suitability for following
sod Equipment requirements Labor
requirements Irrigation requirements
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Understanding tillage
Cutting
Crushing
Milling
Beating
Rebound
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The Native American tillage tradition
The European tillage tradition Full field
tillage High populations of small seeded crops
Low populations of large seeded crops
Zone tillage
http//www.nysm.nysed.gov/IroquoisVillage/sisterst
wo.html
http//www.artchive.com/artchive/V/van_gogh/sower.
jpg.html
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Tillage variables
Depth Area Action Timing
Deep
Shallow
Full field
Zone
Compost aeration
Spading machine
Stale seedbeding
Residue incorporation
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Do you use tillage prescriptively ?
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Prepare a favorable seed bed
http//www.pda.org.uk/image/leaflets/17/pic4.jpg
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NO
Increase rooting zone
Brady and Weil (2002)
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Firm a seed bed
http//www.noble.org/Ag/Horticulture/raisdbed/imag
es/turfroll.JPG
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Shape the soil surface
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Anchor plastic mulch
Prepare for mulch laying
Google Image
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Precision cultivation
http//www.samd.com.au/styne_weeder.html
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Accelerate soil warming
Air
Strip-till
Soil temperature (oF)
No-till
noon
Hour of the day
http//www.progressivefarm.com/html/figure2.html
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Harvest root crops
Ken Fager
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Manipulate soil biology
Conventional tillage
Conservation tillage
Adapted from Hunt et al. (1986)
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The Challenge
Maintaining residues while accomplishing
tillage objectives
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This cultivator will tend to drag surface
residues
High residue cultivators are available !
http//www.hort.cornell.edu/organicfarm/2004galler
y.html
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High residue cultivator
Undercutting sweeps
Coulter
Point
Ken Fager
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No-till planting with a jab planter
http//www.fao.org/News/2000/img/brazil.jpg
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How do we get from here
to here?
Robert Walters
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And eventually end up here?
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The much maligned moldboard plow
Ken Fager
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The dark side of tillage
Google Image
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Which soil has a healthier respiratory and
circulatory system ?
White zones are pores gt 1mm
Tillage pan
No-till soil
Tilled soil
(Young and Ritz, 2000)
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Potential for poor synchrony
N
N
N
Available for loss
Available for loss
Adapted from Robertson et al.
Tillage
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Crop residues Cover Crops Animal manure
Crop residues
20 years of similar tillage intensity but
contrasting levels of organic inputs
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Good tilth
How does your soil respond to tillage ?
Poor tilth
Google Image
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Granular crumb structure
Compacted massive structure
Understanding tilth
Texture
Structure
Moisture
http//www.grdc.com.au/growers/gc/gc48/conference1
.htm
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Some areas of the southeastern US have a
high incidence of soils that are prone to
compaction
Well graded sands are prone to compaction
Well sorted sands resist compaction
AG-353
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Annual sub-soiling is cost effective for some
crops
AG-353
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Successful Tillage
No more than necessary
the right tool(s) the right soil
conditions proper adjustment proper operation
http//www.classic-combines.com/images/tillage20t
rain20-20rear20quarter20view2.jpg
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Can soil biology get the job done ?
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Feed the soil vs. Feed the crop ?
Both strategies are important !
Healthy roots need available nutrients !
Unhealthy roots use nutrients inefficiently
Plants with poorly developed roots tend to have
nutrient deficiency and drought stress symptoms
Acute root disease
Chronic root malfunction
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http//res2.agr.ca/stjean/publication/bulletin/nit
rogen-azote_e.pdf
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Modeling approach to N management
N modeling involves balancing
inputs and outputs
Data and assumptions about multiple N pools are
used to calculate N input rates This approach is
often used by researchers but is rarely used by
farmers
http//res2.agr.ca/stjean/publication/bulletin/nit
rogen-azote_e.pdf
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http//ipm.ncsu.edu/vegetables/CommercialVegetable
s/SECommercialVegGuide.pdf
N
Start with estimating total N uptake
http//res2.agr.ca/stjean/publication/bulletin/nit
rogen-azote_e.pdf
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Consider N uptake patterns
http//edis.ifas.ufl.edu/CV141
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Identify N credits
N credits
Crop residue N
Cover crop N
Compost/Manure N
Soil N
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Many vegetable crop residues are comparable to a
legume cover crop
http//res2.agr.ca/stjean/publication/bulletin/nit
rogen-azote_e.pdf
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Impact of high CN ratio residues on min-N
http//res2.agr.ca/stjean/publication/bulletin/nit
rogen-azote_e.pdf
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How much N will this cowpea cover crop supply to
a subsequent crop ?
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Harvest cowpea biomass from an area of known size
3 lbs fresh cowpea biomass
_at_ 80 moisture -gt 2.5 tons DM per acre
_at_ 3 N -gt 150 lbs N per acre
90 lbs available N
Assume 60 availability
5 ft2
8 ft piece of polytube
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Not all legumes are efficient N fixers !
Efficient N fixation forage legumes,
edamame cowpeas, peanuts
Inefficient N fixation snap beans garden
peas lima beans
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Timing of establishment and termination of legume
cover crops strongly influences their
contribution of N to subsequent crops
Early planting and late termination (after bloom
begins) normally maximizes N contribution to
subsequent crops
http//www.ars.usda.gov/is/pr/2004/041126.htm
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Kill date affects both quantity and timing of N
release
Early kill date 107 lbs total N
Late kill date 131 lbs total N
50 N
lt2 wks
gt6 wks
Wagger (1989)
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Kill date affects both quantity and timing of N
release
Early kill date 107 lbs total N
Early kill date 114 lbs total N
Late kill date 131 lbs total N
Late kill date 140 lbs total N
50 N
2 wks
lt4 wks
Wagger (1989)
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Using manures as a nutrient source
HIGH
Most widely available in NC
http//www.ncsu.edu/organic_farming_systems/news/s
oil_fertility.PDF
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Understanding availability coefficients
gt

http//www.ncsu.edu/organic_farming_systems/news/s
oil_fertility.PDF
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Broiler Litter Basics
http//hubcap.clemson.edu/blpprt/Aub244.html
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Should you be concerned about arsenic ?
Arsenic, in the forms of roxarsone and arsenilic
acid, is an additive in the feed of most broilers
in the US. It is used to control protozoan
parasites known as coccidians and to enhance
weight gain. Feeding arsenic to laying hens is
prohibited. Broiler litter typically contains
30-50 ppm arsenic.
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Using compost as a nutrient source
N availability from mature compost rarely exceeds
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http//www.ncsu.edu/organic_farming_systems/news/s
oil_fertility.PDF
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Application rates of slow release organics should
diminish over time
Single season N availability 25
Tons of compost to supply 150 lbs of N/acre
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How has availability changed after 18
annual applications ?
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Is this graph realistic ?
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20
3 6 9 12 15 18
Years
Adapted from Magdoff and Weil (2004)
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Nutrient management based on N availability may
result in excessive applications of P
Compost 1.7 N 1.2 P2O5
Cummulative P build up in lbs/acre
3000
Most crops remove 5-10 times as much N as P2O5
2000
1000
3 6 9 12

YEARS
Adapted from Magdoff and Weil (2004)
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Long term application of organic nutrient sources
at rates based on single season availability
coefficients is a questionable practice.
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Crop uptake of soil N
Crops often obtain more than half of their N from
SOM in highly fertilized systems
Magdoff and Weil (2003)
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Contrasting N supply from light and dark soils
Producing Vegetable Crops 5th Edition by John M.
Swiader and George W. Ware
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Amino sugar N
No response to additional N
http//cropsci.uiuc.edu/classic/2002/Article9/figu
re1.cfm
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Use supplemental N to balance the budget
N credits
Total N uptake
Crop residue N
Cover crop N
Compost/Manure N
N
supplemental
N
Soil N
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http//anlab.umesci.maine.edu/handout/organ01.HTM
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A variety of high protein by-products can be
purchased in bulk from feed mills for 1- 2
per lb of N
http//www.engormix.com/feather_meal_its_nutrition
al_e_articles_79_GDL.htm
Crude protein / 6.25 total N
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How much does organic N cost ?
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Measuring amendment volume is often more
convenient than weight
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http//res2.agr.ca/stjean/publication/bulletin/nit
rogen-azote_e.pdf
69
Relationship between soil texture and
probability of leaching
http//res2.agr.ca/stjean/publication/bulletin/nit
rogen-azote_e.pdf
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DENITRIFICATION
?
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There must be another way
Modeling is too complicated
In-season sampling of plant and soil N is an
alternative to pre-plant modeling
http//www.sallydunham.co.uk/Large/frustration.jpg
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http//www.westernag.ca/
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http//www.chiletaskforce.com/otherprojects/drip/p
pt/7.htm
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Managing for synchrony
Reduce and delay tillage
Split apply nitrogen and potassium
Use foliar fertilization, fertigation and
combinations of fast and slow release nutrient
sources to synchronize nutrient availability with
crop uptake patterns
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Balancing inflows and outflows
Use soil testing to monitor trends
Estimate field and whole farm mass balances for
N, P2O5 and K2O
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Nutrient budgets on organic farms
a review of published data
N
P
K
http//www.organic.aber.ac.uk/library/Nutrient20
budgets20on20organic20farms.pdf
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Useful Resources
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http//ppathw3.cals.cornell.edu/mba_project/moist/
Roland.pdf
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Roland Bunchs 5 Principles
1) Maximize organic matter production2) Keep the
soil covered3) Use zero tillage4) Maintain
biological diversity5) Feed crop with
decomposing mulch

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http//www.ncsu.edu/organic_farming_systems/news/s
oil_fertility.PDF
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http//www.ncsu.edu/organic_farming_systems/
news/cover_crops.PDF
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http//anrcatalog.ucdavis.edu/pdf/7249.pdf
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