optimizing soil health in season extension environments through innovative cover crop management,...
TRANSCRIPT
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
Soil and nutrient management differs in high tunnel situations!
Nut
rient
nee
ds c
an b
e gr
eate
r
Moisture lim
ited à organic m
atter
can spread moisture farther
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?
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.
“Particulate organic matter” (POM)
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
Particulate organic matter (POM) includes leaf fragments (lf) and root fragments (rf).
Leaf Fragment
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
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)
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
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
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 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
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?
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
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…