4. How much N can a legume fix?
• Fix N over spring, reaching peak at full flower
Cover Crop
Subterranean Clover
Average N content
%N in Maturity
biomass
30-80 lb/acre
2
Mid-April
Crimson Clover
100-150 lb/acre
2.5
Late April
Austrian Winter Pea
100-150 lb/acre
3.5
Early May
Hairy Vetch
150-200 lb/acre
4
Early May
Berseem Clover
100-140 lb/acre
3
Late May
Common Vetch
120-170 lb/acre
3.5
Late May
Nitrogen contents of several winter annual legume cover crops in 2009 and 2010 in NC.
Ranges are approximate and will vary from year to year.
Courtesy of Dr. Julie Grossman, NCSU Soil Science
5. Why use cover crops?
• Fertility
• Weed suppression
– Out compete weeds
– Leaf canopy that suppresses germination
– Allelopathy
6. Why use cover crops? Weed
Suppression
• Seed at high rates
• Don’t let the cover become
a weed.
• “Allelopathy is rarely
amazing”
12. Small Grains:
barley, oats, wheat, triticale
•
•
•
•
•
•
Winter annual grasses (cereal grains)
Scavenge nutrients
Add organic matter
Suppress weeds
Can be grazed
Can be companion planted with legumes
13. Barley, Oats, Wheat, Triticale
Management
• Plant in fall
• Around 100 #/acre for thick cover
– (1/4 # per 100 sq ft)
• Fertility needs are moderate
• To kill:
– Mow, scythe, or roll-kill at milk to soft dough stages of
kernel formation (spring)
– Mow and till (winter or spring)
– Till (winter)
– Oats may winter kill
Oats
14. Rye (Secale cereale)
•
•
•
•
•
•
•
•
•
Winter annual grass
Nutrient catch crop
Large amount of organic matter
Very competitive with weeds
Good companion crop
Can graze
Inexpensive
Very cold tolerant
Earlier maturing than other grass cover crops
15. Rye
Management
• Plant in fall
• Moderate fertility needs
• About 100 #/acre (1/4 # per 100 ft2)or 30-50
#/acre if planting with a legume
• To kill:
– Till (plow/disc) in winter or early spring
– Mow, scyth, or roll-kill when full flower or into
milk-stage (spring: May)
16. Management Cautions
Grain Cover Crops
• Needs adequate
fertility to produce
biomass
• Can tie up nitrogen
when decomposing
• Produce lots of
biomass
• They are grasses
– consider when
planning
rotations
17. Winter Annual: Brassicas
• Mustards, forage turnip, forage radish, rape, canola
• Characteristics: large taproot, varied cold hardiness,
rosettes in winter turn to large stalked plant in spring
• Biofumigant
• Sulfur may be needed
• Don’t do great in sandy soils
• Management:
– Seed 1 to 2 months before first
frost at 5 to 15 lb/acre
(0.03 lb or ½ oz./100 ft2)
½ inch to ¼ inch deep
– To kill – mow and disc
18. Winter Annual Legume: Austrian winter pea
• Also known as field pea (but not in the South)
• High-N fixer (90-150 lb N/acre), lots of biomass,
cold hardy, viney growth,
• Management:
– Drill/plant about ¾ to 1 inch deep (broadcast not
recommended)
– Plant in fall
– 70-90 lb/acre (1/5 # per 100 ft2)
– Kill: Just after full-bloom
• mow, disc, roll-kill, scythe
– Decomposes quickly
– Use correct innoculant
19. Winter Annual Legumes: Hairy Vetch
• Characteristics: viney growth, high Nfixer, cold tolerant
• Management:
– Seed at 20-30 lb/A (0.05 lb/100 ft2)
– in fall (3/4 inch deep)
– Use correct innoculant
– To kill:
• Mow and disc, roll-kill at early seed “set” stage
– Re-seeding/weed issues?
20. Winter Annual Legume: Crimson Clover
• Characteristics: Good N fixer, good beneficial
insect/pollinator habitat, beautiful
• Does not like wet feet
• Matures slightly earlier
• Management:
– Use correct innoculant
– 20-25 lb/acre (0.05 lb/100 ft2)planted in fall, ¼ to ½
inch deep
– To kill:
• Mow and disc
• Mow or roll-kill at late bloom/early seed set
– Will re-seed
21. Other winter annual legumes (that will
work in NC)
•
•
•
•
Berseem clover
Subterranean clover
Woolypod vetch
Cahaba white vetch
22. Management Cautions for Winter
Legumes
• Use correct innoculant
– Nitragin Co., INTX microbials, Johnny’s Select
Seeds, Peaceful Valley Farms, etc.
• Most N is in above ground biomass
• Max N in plant at full-bloom
• N is not readily available to subsequent crop
24. Summer Annuals: Buckwheat
• Characteristics: fast growing, suppresses
weeds, good pollinator habitat, effective
nutrient scavenger
• Succulent plant decomposes quickly
• May go to seed = weed problem in next crop
• Management:
– Frost-sensitive, likes cool weather
– Plant ½ inch deep 30-90 lb/acre
– 0.1 lb/100 ft2
– Kill by mowing or disking (1 week after flowering)
• Can be frost killed (not reliable to prevent re-seeding)
25. Summer Annuals: Sorghum-sudangrass
• Cross between grain sorghum (milo) and sudangrass
• Characteristics: grows well in hot/dry, large biomass
producer, suppresses weeds (allelopathic)
• Management:
– Plant 1-1 ½ inches deep from late spring-midsummer at 45
lb/acre (0.06 lb/100 ft2)
– Can be mowed (or grazed)
– Does well planted with viney legumes
– To kill
• Mow and disc
• Frost kill
– Will tie up N
26. Summer Annual: Millets
• Grasses, companion planted, frost-killed
• German (foxtail) (Setaria italica)
– 2-5 ft tall, small seeded
– Plant mid-May-August at 25-30 lb/acre (0.06 lb/100ft2)
– Avoid sandy soils
• Pearl or cattail (Pennisetum glaucum)
– 4-12 ft tall and performs well in sandy soils
– Plant late April-July at 5 to 15 lb/acre (0.02 lb/100ft2
– Harder to kill
• Japanese (Enchinochloa frumentacea)
– 2-4 ft tall and quick maturing
– Plant April to July at 20-25 lb/acre (0.05 lb/100ft2)
– Avoid sandy soils
27. German (foxtail) Millet
From Iowa State Univeristy
From Western Illinois State University
Japanese Millet
From Texas A&M University
28. Summer Annual: Sunflowers
• Characteristics: Tall, weed suppressive, pretty
• Management:
– Plant in warm soils at 4-5 lb/acre (0.01 lb/100 ft2)
½ - 1 inch deep
– Modest fertility needs
– Variety selection: cheapest seed or whatever
looks pretty
– To kill:
• Mow, disc
• Frost-kill
29. Summer Annual Legume: Cowpeas
• Also called black eyed, southern, crowder, and
field pea
• Characteristics: can produce 90-100 lb N,
succulent, decomposes quickly, can be viney,
need warm weather
• Management:
– Plant 40-100 lb/acre (up to ¼ lb/100 ft2)
– ‘Ironclay’ or ‘Red Ripper’ recommended
– To kill:
• Mechanical means not reliable
• Frost-killed
30. Summer Annual Legumes: Soybean
• Characteristics: 2-4 ft
tall, bushy, inexpensive, high N-fixer, forage
types available
• Management:
– Plant 60-100 lb/acre (up to ¼ lb/100 ft2)when soil
warms
– Plant late-maturing varieties (Group VI or later)
– To kill:
• Mow and disc
• Frost-killed
31. Alternative Summer Annual Legumes
• Velvetbean (Mucuna deeringiana)
– Viney legume (good in combinations)
– does well in sandy/poor soils
• Sunhemp (Crotalaria juncea)
CEFS, NC State University
– Very tall, herbaceous annual that needs good
drainage
CEFS, NC State University
– Recommended to plant after summer
crop (like corn) to grow in months up
to first frost
• Seed for these plants is hard to find
and can be expensive
32. Perennial Cover Crops
• Paths, between rows (“living mulch”), forage/hay, long-term
planning
• Options:
– Alfalfa: short-lived perennial
•
•
•
•
Can be mowed or grazed
Needs well-drained, near neutral soil
Seed in fall
Most susceptible to pests
– White clover (Trifolium repens): perennial
• Seed in late summer/fall
• Choose intermediate sizes (i.e. Dutch white)
• Can be mowed, grazed, trafficked
– Red clover (Trifolium pratense): short-lived perennial
• Mammoth red (can be cut once) or medium red (multi-cut)
• Seed in fall
• Kill mechanically when in bloom or dormant
34. Organic No-till
• Winter annual cover crop is roll-killed
• Cash crop planted into rolled cover
• Need a lot of biomass (8,000 lb dry matter/A or
over 18 lb/100 ft2)
– Don’t attempt with poor or spotty stands
• Roll at full bloom or just beyond
• Roller-crimper, cultipaker, scythe, mower, etc.
• Need to get through cover crop mat to plant
35. Kill timing for legume cover crops
MATURITY
Early
Mid
SPECIES
none
Crimson clover
Late-April/
Early May
Late
TIME
Mid-April
Late-April/
Early May
Hairy vetch
AU Earlycover
Late-May
Hairy vetch
AU Merit Experimental USDA
line
Late-May
Early June
Early June
Mid June
Hard-to-kill
Not winter hardy
CULTIVAR
none
AU Robin Dixie
AU Sunrise Tibbee
Winter pea
Common vetch
Berseem Clover
Sweet clover
Sub clover
Blue Lupine
Winter hardy Earlycover
(unstated) and Whistler
(unstated)
Bigbee
Hubam
Denmark
Tifblue 78
Courtesy of Chris
36. Kill times for rye (Secale cereal) cover
crops
MATURITY TIME
Early
CULTIVAR
Late April Wrens Abruzzi
Wrens 96
MatonII
Mid
Early May Aroostook
Late
Mid to late Rymin
May
Wheeler
38. Rules of thumb for planting in no-till
• Need to get through thick mat of rolled cover
• Use straight edged no-till coulters.
• Heavy duty downforce springs or a pneumatic
downforce system is often needed.
• Some planter may need extra weight mounted on
the frame.
• Cast iron and rolling spider closers are reported
to be the best choices. Even with the heaviest of
closers, sealing the trench can be difficult at
times.
39. How much N am I getting?
• Nearly all N comes from above ground biomass
• Material must decompose for crop to get N
• About 50% of N will be available for next crop
(40% if residue left on surface)
Cover Crop
Subterranean Clover
Average N content
%N in Maturity
biomass
30-80 lb/acre
2
Mid-April
Crimson Clover
100-150 lb/acre
2.5
Late April
Austrian Winter Pea
100-150 lb/acre
3.5
Early May
Hairy Vetch
150-200 lb/acre
4
Early May
Berseem Clover
100-140 lb/acre
3
Late May
Common Vetch
120-170 lb/acre
3.5
Late May
Nitrogen contents of several winter annual legume cover crops in 2009 and 2010 in NC.
Ranges are approximate and will vary from year to year.
40. How much N am I getting?
1. Determine biomass produced.
– Use a frame of known dimensions, clip plants at
ground level, dry plants to crunchy dry
– Calculate:
•
Area sampled: 2x2 = 4 sq.ft. x 2 (samples) = 8 sq.ft.
2 ft
2 ft
•
•
Dried samples weigh 1.2 lbs.
1.2 lbs/8 s.f. X 43,560 s.f./acre = 6,534 lbs dry biomass
41. 2. Use tissue test or estimate %N in cover crop
– Multiply dry biomass yield with % of Nitrogen
(6453 lbs/acre) x (0.035) = 226 lb of N in biomass
3. Predict how quickly biomass will decompose,
releasing nutrients for crop
– Multiply legume biomass nitrogen with :
• 0.50 if residue will be incorporated
• 0.40 if residue is left on surface
– (226 lb N) x (0.50) = 113 lb N/acre available to crop
Cover Crop
Subterranean Clover
Average N content
%N in Maturity
biomas
s
30-80 lb/acre
2
Mid-April
Crimson Clover
100-150 lb/acre
2.5
Late April
Austrian Winter Pea
100-150 lb/acre
3.5
Early May
Hairy Vetch
150-200 lb/acre
4
Early May
Berseem Clover
100-140 lb/acre
3
Late May
Common Vetch
120-170 lb/acre
3.5
Late May
42. Seed Sources
•
•
•
•
•
•
•
•
Local feed and seed
Southern States
Dirtworks.net
Improved Forages
Johnny’s Selected Seed
Albert Lea Seedhouse
Blue River Organic Hybrids
Welter Seed and Honey Co.
Innoculant Sources:
– Nitragin Co., INTX microbials
43. Further resources
• Bowman, G., C. Shirley, and C. Cramer. 1998. Managing Cover Crops Profitably. The
Sustainable Agriculture Network Handbook Series, Book 3. Available from
Sustainable Agriculture Publications, Hills Building, Room 10, University of
Vermont, Burlington, VT05405-0082.
(http://www.sare.org/handbook/mccp2/index.htm)
• SAREP cover crop database: http://www.sarep.ucdavis.edu/database/covercrops
• Hoyt, Wagger, Crozier. 2004. Soilfacts: Winter Annual Cover Crops (AGW-439-58);
www.soil.ncsu.edu/publications/Soilfacts/AGW-439-58/AGW_439_58.pdf
• Creamer, Baldwin. 1999. Summer Cover Crops; http://www.ces.ncsu.edu/hil/hil37.html
• Growing Small Farms: Cover crops for sustainable production:
growingsmallfarms.ces.ncsu.edu/growingsmallfarms-covcropindex/
• NCSU Organic Grain Program:
http://www.organicgrains.ncsu.edu/cropproduction/covercrops.htm
• ATTRA: Overview of cover crops and green manures: https://attra.ncat.org/attrapub/summaries/summary.php?pub=288
• Oregon SU Small Farm cover crop calculator:
http://smallfarms.oregonstate.edu/calculator
• NCDA Plant Tissue Analysis (Agronomic Division):
www.ncagr.gov/agronomi/uyrplant.htm
• NCSU Small Grains: www.smallgrains.ncsu.edu