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Optimizing soil health in season
extension environments through
innovative cover crop management
Julie Grossman
Department...
Soil and nutrient management
differs in high tunnel situations!
Nutrientneedscanbegreater
Moisturelimitedàorganicmatter
c...
High tunnels are more
intensively managed
•  Increased soil nutrient removal
•  Increased traffic
•  Extended season promo...
Solid
fraction
Pore
space
Organic matter: All
living or formerly living
material in a soil
Organic matter influences
soil structure, nutrient
storage, biological activity,
water and air infiltration,
erosion! Wow!...
Plant	
  residue	
  
Readily	
  
decomposable	
  
(ie,	
  “POM”)	
  	
  
decomposi;on	
  
Plant	
  
available	
  N	
  
Mic...
Par;culate	
  Organic	
  MaEer	
  (POM)
Particulate organic matter (POM) includes leaf
fragments (lf) and root fragments (rf).
Leaf Fragment
Jones et al.,
C = Mucilage
halo, stained
with analine
blue
How does soil quality differ after
8 years of HT production?
Conventional
management
Organic
Management
Measure of soil
qu...
0
1000
2000
3000
4000
5000
6000
7000
Total soil N Readily
Mineralizable
Carbon
Basal
respiration
Microbial
biomass
Organic...
How does organic management
differ?
•  Synthetic water-soluble
fertilizer used
•  Delivered through
fertigation
•  Deliver...
Hairy Vetch: AU Early
Cover (Auburn Univ),
winter hardy Early Cover
(NY), AU Merit
Austrian Winter Pea,
Whistler and Varie...
Crop residue
Available Nitrogen
Decomposition
Legume based cropping system
N2
Biological
Nitrogen
Fixation
Four cover crop single
species and mixtures
Sown in two locations:
•  North Central Research
and Outreach Center
(Grand Ra...
Mow
Early
Plant
greens ($$)
Mow
Late
More biomass
and N
Spring 2015 each plot
split by:
•  Early mowing to
additional cash...
Data we will collect
•  Cover crop biomass
•  Harvestable yield
•  Soil quality
measures:
–  POM
–  Permanganate
oxidizabl...
Shoveling snow into open tunnel in
Grand Rapids for improved plant
protection… (Dec, 2014)
…however, snow was melted by mi...
Evidence of winter kill of vetch/rye
mix in Morris (Jan, 2015)
Optimizing soil health in season extension environments through innovative cover crop management, 2015.
Optimizing soil health in season extension environments through innovative cover crop management, 2015.
Optimizing soil health in season extension environments through innovative cover crop management, 2015.
Optimizing soil health in season extension environments through innovative cover crop management, 2015.
Optimizing soil health in season extension environments through innovative cover crop management, 2015.
Optimizing soil health in season extension environments through innovative cover crop management, 2015.
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Optimizing soil health in season extension environments through innovative cover crop management, 2015.

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by Julie Grossman, Assistant Professor | Department of Horticultural Science, University of Minnesota

Presented at the 2015 Minnesota Statewide High Tunnel Conference.

Published in: Education
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Optimizing soil health in season extension environments through innovative cover crop management, 2015.

  1. 1. Optimizing soil health in season extension environments through innovative cover crop management Julie Grossman Department of Horticultural Science University of Minnesota, Twin Cities Co-PI’s: Mary Rogers, Steve Poppe
  2. 2. Soil and nutrient management differs in high tunnel situations! Nutrientneedscanbegreater Moisturelimitedàorganicmatter canspreadmoisturefarther
  3. 3. High tunnels are more intensively managed •  Increased soil nutrient removal •  Increased traffic •  Extended season promotes back-to-back cash crops What is the impact of this increased management on soil quality after many years?
  4. 4. Solid fraction Pore space Organic matter: All living or formerly living material in a soil
  5. 5. Organic matter influences soil structure, nutrient storage, biological activity, water and air infiltration, erosion! Wow! From http://kearney.ucdavis.edu/OLD%20MISSION/Old%20MAIN.htm Soil organic matter (SOM) is the organic (C-containing) soil component. “Particul ate organic matter” (POM)
  6. 6. Plant  residue   Readily   decomposable   (ie,  “POM”)     decomposi;on   Plant   available  N   Microbial   Biomass   Stable   humus   Decomposi;on  of  organic  materials,  like   plant  residues,  promotes  soil  organic  maEer   development     •  Decomposition rate is controlled by: •  Residue biochemistry •  Association with decomposer microorganisms •  Climatic conditions; temperature and moisture
  7. 7. Par;culate  Organic  MaEer  (POM)
  8. 8. Particulate organic matter (POM) includes leaf fragments (lf) and root fragments (rf). Leaf Fragment
  9. 9. Jones et al., C = Mucilage halo, stained with analine blue
  10. 10. How does soil quality differ after 8 years of HT production? Conventional management Organic Management Measure of soil quality HT Field HT Field pH 7.8 7.0 7.7 7.6 Salinity: EC (dS m-1) 0.16 0.065 0.30 0.059 Total C (g kg soil-1) 17.5 19.3 22.4 22.4 POM C (g kg soil-1) 1.65 1.51 4.2 3.02 Knewtson et al, 2012
  11. 11. 0 1000 2000 3000 4000 5000 6000 7000 Total soil N Readily Mineralizable Carbon Basal respiration Microbial biomass Organic Conventional (µg C02-C) (µg C02-C) mg per kg-1 Reeve and Drost, 2012 Organic Management Increases Soil Biological Properties in High Tunnels (µg C02-C)
  12. 12. How does organic management differ? •  Synthetic water-soluble fertilizer used •  Delivered through fertigation •  Delivered directly to root zone •  Various pre-plant incorporated composts and plant residues •  Ideally coupled with fertigation using OMRI approved sources –  More expensive –  Can clog drip lines Conventional Nutrient Management Organic Nutrient Management
  13. 13. Hairy Vetch: AU Early Cover (Auburn Univ), winter hardy Early Cover (NY), AU Merit Austrian Winter Pea, Whistler and Variety unstated http://aggie-horticulture.tamu.edu/extension/Texascrops/foragelegumes/index.html, NCAT White Lupin, TifBlue78 Crimson Clover:AU Robin, AU Sunrise,Tibbee, Dixie Subterranian clover, Denmark Berseem clover, Bigbee Hairy Vetch, Purple Prosperity, USDA Cover Crops
  14. 14. Crop residue Available Nitrogen Decomposition Legume based cropping system N2 Biological Nitrogen Fixation
  15. 15. Four cover crop single species and mixtures Sown in two locations: •  North Central Research and Outreach Center (Grand Rapids, MN) •  West Central Research and Outreach Center (Morris, MN) Austrian winter pea with rye (50-75 lbs/acre) Red Clover (10-12 lbs/acre) Winter rye, hairy vetch, fall radish (50-75 lbs/acre) No cover crop control
  16. 16. Mow Early Plant greens ($$) Mow Late More biomass and N Spring 2015 each plot split by: •  Early mowing to additional cash crop (More $$?) •  Late mowing for increased cover crop growth (More N??) •  Cost benefit analysis Should you take advantage of the spring to grow more N, or grow more crop?
  17. 17. Data we will collect •  Cover crop biomass •  Harvestable yield •  Soil quality measures: –  POM –  Permanganate oxidizable C (“POX”) –  EC –  Available N •  Outreach activities: –  Field days –  On-farm trials in 2016
  18. 18. Shoveling snow into open tunnel in Grand Rapids for improved plant protection… (Dec, 2014) …however, snow was melted by mid January (Jan, 2015) Initial challenges…
  19. 19. Evidence of winter kill of vetch/rye mix in Morris (Jan, 2015)

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