Steps to Success with Cover Crops Scott Nelson Director of Agronomy Center for Farming Innovation [email protected]
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Steps to Success
with Cover Crops
Scott NelsonDirector of Agronomy
Center for Farming Innovation
Advancing Profitability
and Stewardship
Center for Farming Innovation
Why Care About Cover Crops?
#1. Reduce Erosion/Improve Soil Health
Cumulative Soil Loss from 2008 to 2019 (Dump trucks/Acre)
Areas of high soil loss
Consequences of soil loss are greater on these soils.
Source: calculated from Daily Erosion Project, ISU
Average Soil Loss in Iowa: 4.3 Dump Trucks of Soil Loss per Acre/Decade
AVERAGE TOPSOIL LOSS IN IOWA OVER THE PAST DECADE
Source: Calculated from Daily Erosion Project data sets.
Topsoil
US is losing topsoil 10 times faster than it is being replaced.
Takes 500 years to replenish one inch of lost topsoil.
Soil is not a renewable resource.
Acres of US Farmland Over Time(US Census of Agriculture)
360000000
370000000
380000000
390000000
400000000
410000000
420000000
430000000
440000000
450000000
2017 2012 2007 2002 1997
Acr
es
of
Farm
lan
d
With declining acres of farmland,
protecting our farmland is more
important than ever.
Cover Crops Significantly Reduced Soil Compaction across all depths. Data is across 5 environments after three years of continuous cover cropping.
Soil Depth (inches)
0 2 4 6 8 10 12 14
Pen
etr
ati
on
Resis
tan
ce (
PS
I)
70
80
90
100
110
120
130
140
150
Cover CropNo Cover Crop
Improve Soil Health
#2. Reduce Nutrient LossesGULF COAST HYPOXIA
N- LOST ANNUALLY TO THE MISSISSIPPI
5.1 billion pounds
$969M in fertilizer value
5.1 billion pounds = 18,000 rail cars of fertilizer.
Cover Crops Reduce Nitrogen from 30 to 50%
Cover Crops and Water Quality5 year Study
N-CONCENTRATION TOTAL NITROGEN LOAD
0
2
4
6
8
10
12
14
No Cover Crop Cover Crop
Nit
rate
(p
pm
)
0
5
10
15
20
25
30
35
40
45
No Cover Crop Cover Crop
Tota
l Nit
roge
n L
oad
(lb
s/A
)
Ag Water Mnmnt 110:25-33, 2012
#3. Sometimes there is a yield advantage to cover crops.
38
43
35
36
37
38
39
40
41
42
43
44
No Cover Crop Cover Crop
Yiel
d (
Bu
/A)
Effect of Manure + Cover Crops on Corn Yield
-15
-10
-5
0
5
10
15
Yie
ld A
dva
nta
ge (
Bu
/A)
Location Number
University of Minnesota Study
Why the positive response?
Corn Yield ResultsUrea based program
Soybean Yield Results
#4. Simplify Weed Spectrum
1. Reduce erosion/Improve Soil Health
2. Reduce Nutrient Losses
3. Potential Profit/Yield Advantage
4. Herbicide Resistant Weeds
Steps to Success with Cover Crops
▪Cereal Rye- most winter hardy and provides the most biomass
▪Wheat/Triticale- less biomass, but easier on corn
▪Cover Crop Mixes: probably not worth the expense unless seeded early-IMHO
Steps to Success with Cover CropsEstablishment
▪Inter-seed into standing crop from mid August to mid September
▪Do not inter-seed if conditions are dry and hot.
▪Drill soon after harvest
Steps to Success with Cover Crops
Seeding Rates
▪30-40 lbs/A if erosion control is goal.
▪Up to 60 lbs/A if weed control is the goal.
▪Consider 30-40 lbs/A ahead of corn and 40-60 lbs/A ahead of soybeans
Steps to Success with Cover Crops
Termination
▪Soybeans: Plant green and terminate a few days before or after planting to optimize weed control.
▪Corn: Terminate 2 weeks before planting or when cover crop < 12 inches tall.
Roller Crimping the Crop
Steps to Success with Cover CropsPlanter Set Up
▪No-till planter equipped with residue movers
▪Hydraulic downforce pressure recommended
▪Starter fertilizer is desirable but not necessary
Nitrogen Form and Placement Must be Different when Following Cover Crops
Soil Nitrate at Time of Termination
30
36
15
9
0
5
10
15
20
25
30
35
40
Study 1 Study 2
Nit
rate
(p
pm
)
No Cover Crop RCC
Sources: Soil Sci Society Jrn 79:1482-1495, 2015; Agronomy J 111:1-11, 2019
Need to Overcome Early Immobilization to Optimize Yield
50% of total nitrogen as nitrate form at or soon after planting
▪Coulter inject UAN preplant or early sidedress
▪Ammonia fb Starter UAN
▪Ammonia Nitrate Sulfate or AMS
Fertilizer Form Matters in No-Till and Cover Crops
Amount of Urease Enzyme in Tilled and No-Till Field
0
50
100
150
200
250
Soil 1 Soil 2 Soil 3
Ure
ase
en
zym
e (
ug
/g)
Tilled Soil No-Till Soil
Nitrogen lost to volatility
0
200
400
600
800
1000
1200
Soil 1 Soil 2 Soil 3
Am
mo
nia
loss
(m
g N
)
Tilled No-Till
No-Till Corn Study
211
140
175
0
50
100
150
200
250
Ammonia Nitrate Urea Agrotain
Yie
ld (
Bu
/A)
Averages across 6 locations and two years. Agron J. 110:1439-1446, 2018
N Form in No-till Corn
109
158
149144
100
110
120
130
140
150
160
170
No N AmmoniumNitrate
Urea UAN Solution
Yie
ld (
Bu
/A)
Agron. J. 85:893-897
For poorly drained soils, consider Strip Till with Cover Crops
• There remains many agronomic challenges to cover crops.
• Farmers and Society are looking to us to fix these challenges.
Using Fluid Fertilizers to Close the Yield Gap in Corn Following Cereal Rye.❑Cover Crop vs No Cover Crop
❑Dual placement vs Single Starter Placement
❑Starter plus Sulfur
❑Nitrogen Form, Placement, Timing
Fluid Fertilizer Foundation Sponsored
Research
Treatment Number
Treatment
1 Fall applied Anhydrous Ammonia at 150 lbs N/A- no cover crop
2 Fall applied Anhydrous Ammonia at 150 lbs N/A- with cover crop
3 Spring applied Anhydrous Ammonia at 150 lbs N/A- with cover crop
4Spring apply 32% at 34 gal/A (100 lbs N) applied as coulter preplant+ Planter applied
starter in a band as 32% UAN at 17 gal/A (50 lbs N/A) using 2X2 placement
5Spring apply 32% at 34 gal/A (100 lbs) applied as coulter preplant+ Planter applied
starter in a band as 32% UAN at 17 gal/A (50 lbs N/A) using Conceal System
6Spring apply 32% at 34 gal/A (100 lbs N) applied as coulter preplant+ Planter applied
starter in a band as 15-6-3-2.40s Blend at 32.3 gal/A (50 lbs N/A, 20 lbs P/A, 10 lbsK/A, 8 lbs S/A) using Conceal (Precision Planting) attachment.
7Spring apply 32% at 34 gal/A (100 lbs N) as coulter preplant fb 25.5 gal/A (75 lbs) 32%
UAN at V4 to V6 applied with coulter
8Spring apply 32% at 34 gal/A (100 lbs N) as coulter preplant. Broadcast after planting
SuperU at 110 lbs/A (50 lbs N).
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