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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 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, 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)