crop rotations historically revolved around legumes
TRANSCRIPT
crop rotationsHistorically
revolved around LEGUMES
Cover crops
less
Adapted from Sarrantonio (1994)
Broccoli Lettuce
Finding the right times to fit in cover crops
Summer Fallow
Spring Summer Fall
= cover crop
A = cover crop seeded after spring crop harvested, tilled in before fall cropB = cover crop overseeded into spring crop, tilled in before fall cropC = Cover crop allowed to grow in strips when fall crop is young
A
B
C
Wisconsin Integrated Cropping Systems Trial.
1 Gross margins are calculated by taking the gross revenue per acre (yield times price at harvest) minus variable costs of production (seed, fertilizer, pesticides, drying costs, fuel, and repairs).
Wisconsin Integrated Cropping Systems Trial.
CS1 = continuous corn CS2 = corn/soybean CS3 = corn/soybean/wheatCS4 = 1 year corn/3 years alfalfa CS5 = corn/alfalfa/alfalfa-oats-peas
Wisconsin Integrated Cropping Systems Trial
Energy relationships
High energy cost of N fertilizer
Why is the net energy gain for ethanol (~ 1.2) so much lower than all of these ?
Highest energy
input and output
Lowest output:input
ratio
How much N can frost seeded red clover fix ??
Red clover frost seeded into winter wheat.
Seed is broadcast onto frozen and cracked soil in mid-March after snow melt. Seedlings remain relatively small until wheat harvest, at which time they have full sunlight and three months to grow and fix atmospheric nitrogen. Total nitrogen accumulation typically exceeds 100 lbs./a
by the end of the growing season.
Hairy vetch can be successfully planted after wheat harvest. On the two occasions (out of 18 site-years
of the WICST trial) when the red clover failed to establish well, the vetch produced an average of
115 lbs./a of nitrogen, providing an excellent “back-up plan” that reduces one of the potential risks of
relying on a companion-seeded cover crop for nitrogen. Late July vetch plantings can be riskier
than frost seeding clover.
Cover crops can be managed economically !
When the cost of purchased nitrogen is low, the value of the nitrogen alone does not usually justify the cost of a legume.
However, other benefits such as reduced herbicide use, improved yield of other crops, reduced nitrate leaching, improved soil structure, diminished erosion and reduced
fossil fuel use make cover crops more attractive. As energy prices increase, cover crops become increasingly more
attractive.
Cover crops can provide most or all of the nitrogen required by corn growth.
WI trials to determine whether supplemental nitrogen was worthwhile found that additional nitrogen (either starter or sidedressed) produced a significant yield
increase only about one-fourth of the time. The exceptions always occurred during years with cool
springs, when there is a slow release of legume nitrogen.
WICST scientists recommend that producers perform the pre-sidedress nitrate test when
cover crop growth is modest or spring weather is particularly cool, and use recommended
rates of sidedress N accordingly. (When justified, sidedress N was more
economic than starter N.)
Use supplemental N to balance the budget
Total N uptake Cover crop N
Crop residue N
Soil N
N credits
supplementalNN
Compost/Manure N
Many vegetable crop residues are comparable to a legume cover crop
http://res2.agr.ca/stjean/publication/bulletin/nitrogen-azote_e.pdf
Residues with a low C:N ratio that decompose quickly can release N even though they are not legumes
http://talk.newagtalk.com/forums/thread-view.asp?tid=73097&mid=521773#M521773
We've done some PSNT tests with and w/o fall seeded radish. Kind of a moving target (year to year) in N credits, but I will say that we've always had a bigger credit following radish than what we had without. That could be for a lot reasons. Weather, soil types, temp, etc. I've had an increase of almost 80#s of N using radish vs none, and I've had an increase of 20# vs none.
N credit is a very nice benefit of using a cover like radish, but I also like the other benefits from radish we've observed. Trouble with cover crops is putting a $ benefit on many of them. I can hardly ever say that if I spend 10 bucks on a particular cover, it'll for sure give me 20 back next year. In the big picture, I feel that if looked at over say a 5 or 10 year period, we've put more money in the bank by using covers than we've spent. I don't know how to quantify things $ wise like the value of increased OM, for example.
Pat Sheridan (Fairgrove, Michigan)
LocationCover Crop
Grain Crop
0 lb N/ac
60 lb N/ac
180 lb N/ac
240 lb N/ac
HortinHairy Vetch
Corn 169 184 180 184
Hortin Fallow Corn 105 142 162 164
Hortin Rye Corn 65 102 119 120
HortinHairy Vetch
Sorghum 90 97 99 100
Hortin Fallow Sorghum 74 87 94 92
Hortin Rye Sorghum 54 72 77 74
http://frec.cropsci.uiuc.edu/1993/report13/table10.htm
U of I on-farm covercrop research(grain yields = bu/acre)
Cereal rye often suppresses corn and sorghum yields
Impact of hairy vetch and rye cover crops on corn yield in IL
More crop residues = more OM
CC
CC
20 years of similar tillage intensity and C inputsbut contrasting types of organic inputs
Crop residuesCover Crops
Animal manure
Crop residues
Understanding cover crops as nutrient sources
Early kill date = 114 lbs total N
Late kill date = 140 lbs total N
Wagger (1989)
50% N
Late kill date = 131 lbs total N
Early kill date = 107 lbs total N
2 wks<4 wks
http://www.ars.usda.gov/is/pr/2004/041126.htm
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
in the sprin
g
AC Greenfix was the top N fixer in a recent studylb
s of
N /
acr
e
DO NOT PLANT AC GREENFIX WHERE SOYBEANS WERE GROWN THE YEAR BEFORE
- AC GREENFIX WILL NOT DO WELL!
Like most legumes, AC Greenfix grows slowly for the first 30-40 days.
Weeds can be controlled by mowing or grazing when AC
Greenfix starts to flower or during the first week of flowering. This will make the AC Greenfix tiller out faster and grow
faster, resulting in a better stand.
For maximum nitrogen availability to the following crop, the plants should be incorporated before seedpods begin to filling.
Important considerations
Is the N fixed by AC Greenfix
free ?
Seed cost ~ $40/acrePlanting cost ~ $20/acre
Incorporation cost ~ $10/acre
Total cost ~ $70/acre
Assuming ~100 lbs of N fixed per acre, the cost is ~70 cents per lbs of N
Multi-functional cover crops
Cover Crops
Adapted from Magdoff and Weil (2004)
Cover crops generally require more management
Cover crops are not idiot –proof
There are few profits in idiot-proof systems!
Impact of cover crops on soybean cyst nematodes
Bare Cereal Rye Ryegrass
1 7533 717*117**
2 3650 320* 0**3 1559 722* 386*4 1202 390* 279*
2 years /3 replications
* Significant .05 ** Significant .01
_____________Egg count ______________
M Plumer
Site
Soil Density (g/cm3)all no-tilled 9+ years
Ryegrass cover crop
for 6 years
10” 1.49*
16” 1.58
24” 1.48*
No cover crop
1.66
1.54
1.65
* sig. .05
M Plumer
http://www.amazingcarbon.com/PDF/Rick%20Maurice%20-%20RTM%20Carbon%20Forum%20Sept%202005.pdf
Miscanthus
Aerial Seeding Turnips, Oats and Rye 8-20-2001
Cliff Schuette
Turnipsand Cereal Rye
Airseed 8/25/2000
Barkant Turnips-3 lbsRye 2 Bu
Airplane $8/AcreCorn 183 Bu/acre
Atrazine 1 lbPartner April 28
November 1, 2000Turnips - Spring Oats-
Corn StalksSeeded August 15
Turnips- 4 lbsOats 1 Bu.40 LBS N
November 1, 2000Spring Oats -Cereal Rye-
Corn StalksSeeded August 15
Oats- 1 Bu.Rye-1 1/2 Bu.
40 LBS N
11/30/00
Protein 16.59RFV 114
01/19/2001
Protein 12.79RFV 92
Paul Smith
Annual Rye grass
aerial seededinto standing
corn
Fall, 2001
John HebertInspecting Ryegrass No-till into
corn stubbleFall, 2001
Pluribus strip-till system in cereal rye
Dick Thompson