Assessing Nitrogen Release From Cover Crop and Manure

Shalamar ArmstrongSoil Conservation and Management

Assistant Professor of AgronomyPurdue University Department of Agronomy

Planting Corn

Last Year Corn Residue

Cover Crop Residue

What Should I Know about

My Cover Crop Residue?

How much biomass did I

get?

How much N and C is in my

Cover Crop Biomass?

Will this Cover Crop Biomass

affect my crop N uptake?

How Much Cover Crop N will be

Release to my Crop?

How and when will the my soil

microbes respond to this cover crop

residue?

While planting, what is on this farmer’s mind about his residue?

Understanding the Influence of residue C:N ratio will

give you insight on cover crop and N management

questions

What is C:N ratio and Why is it Important?• The C:N ratio is the amount of Carbon in the residue divided by the

amount of Nitrogen in the residue.

• The C:N ration is important because it gives you an indication of the quality of the residue. High quality residue is easily broken down by soil microbes.

• C:N ratio Thresholds to remember• Greater than 24:1 (Low Quality Residue)

• Lower than 24:1 (High Quality Residue)

• The quality of the controls decomposition and the release of Carbon and Nitrogen into the soil.

How does Residue C:N Ratio Effect the N Cycle

C:N Ratio Impacts• N quality of the residue• The rate of

decomposition• The rate of N release• The quantity of N

release• The quantity of N taken

from soil solution

C:N Ratio and N Immobilization and Mineralization

This example assumes that residue with a 60:1 C:N ration residue is added to soil

: temporary removal of soluble N from the soil solution.

: addition of soluble N to soil solution.

What growth stage is this corn seeing this nitrate?

C:N Ratio Influence on N Release from Cover Crop Residue

Cover Crops Residue N ReleaseCorey Lacey, Clayton Nevins, Houston Miller, and

Shalamar Armstrong

Methods

Spring Collection of Cover Crop Residue

Cover Crop Residue Air DriedPrepared Cover Crop Litter

BagsPlaced Cover Crop Litter Bags

Cover Crop Carbon Decomposition

0 1000 2000 3000 4000

0

10

20

30

40

50

60

70

80

90

100

Decomposition Degree Days

Perc

ent

of

Init

ial C

arb

on

Rel

ease

d

2017 Cover Crop Carbon Release

CR TnT

CR SD

HV TnT

HV SD

MIX TnT

MIX SD

CR= Cereal Rye HV = Hairy VetchTnT= Transitional No-tillSD= Spring Disk

Cereal Residue Nitrogen Tracking N Study

Corey Lacey, Michael Ruffatti, and Shalamar Armstrong

(NREC Poster)

Cereal Residue Nitrogen Tracking N Study

Corn MaturityCover Crop Growth

Cover Crop Decomposition

N

N

N

N

N

N

N

15% Plant Available N

<1% Microbial Biomass N

58% decomposed unmineralized N

27% undecomposed unrecovered N

Changes in Soil Nitrogen Availability During the Life Cycle of Cereal Rye

Adaptive ManagementChallenge

Armstrong, 2018

0

10

20

30

40

50

60

70

80

0 5 10 15 20 25 30 35 40 45

Total Inorganic Nitrogen (kg N ha-1)

Dep

th (

cm

)

Control

Cereal Rye

Impact of Cover Crops on Spring Soil Nitrogen Distribution

3 Year Average

Corn Growth Stage

V6 V12 VT R6

Co

rn N

Up

take

(kg

ha

-1)

0

50

100

150

200

250

300

Non-Cover Crop Cover Crop

60-75 days after CR termination

Cereal Rye Impact on Corn N Uptake

(3.5% OM Mollisol)

66 lbs/A

Timber Soil Southern IN (2.1% OM)

0.00

50.00

100.00

150.00

200.00

250.00

300.00

350.00

V2 V3 V6 V7 V11 R1-R2 R6

Co

rn N

up

take

(kg

N h

a-1)

Growth Stage

CR 0N

Non-CR 0NCR vs. non-CR *

71 lbs/A

Sidedress

Adaptive N Management: N Application Timing

Optimization of Starter N Fertilizer for Corn following Cereal Rye

Shalamar Armstrong, James Camberato, and Robert Nielsen.

Impact of Starter N Corn Yield Following Cereal Rye

Corn Yield Impacts….

• At 1 of 3 sites, CR significantly reduced corn yield (2.4 -9.2 % reduction)

• At 2 of 3 sites, adding 56 kg N ha-1 (50 lbs/A) resulted in equal or greater corn yield relative to the non-CR no starter N control.

• Within CR treatments, at 3 of 3 sites, adding 28-56 kg N ha-1 starter resulted in greater yield (1.3-13.4% greater).

Adaptive N Management: Manure Management and Cover Crop Selection

Objectives

Objectives

• To examine the performance of individualcover crop species in increasingly complexmixtures as a function of manureapplication timing.

• To determine if the inclusion of Red Cloverand swine manure could generate anitrogen fertilizer credit.

Objectives

NEPAC: Morley Clay Loam, Morley Loam, Glynwood Loam

DPAC: Pewamo Silty Clay Loam, Blount Silt Loam, GlynwoodSilt Loam

Objectives

Treatments

1. CSC (N rate: 185 lbs/A)

2. SWC Control-No Manure (N rate: 185 lbs/A)

3. SWC Manure (N rates: 150 and 85 lbs/A)

4. SWC 10% RC-10%R-20%DR-60%Oats (N rates: 150 and 85 lbs/A)

5. SWC 30% RC-70% DR (N rates: 150 and 85 lbs/A)

6. SWC 70% RC-30% DR (N rates: 150 and 85 lbs/A)

7. SWC 100% RC (N rates: 150 and 85 lbs/A)

Objectives

Cover Crop Planting:DPAC 8/21/2017NEPAC 9/6/2017

Manure Application (5,000 gal/A swine manure):NEPAC 9/30/2018 DPAC 12/19/2018

Corn planting: Mid April for each site

• Early application of manure reduce the presence of red clover and increased the presence of volunteer wheat and weeds

• Late manure application resulted in a greater presence of red clover and a reduction of volunteer wheat and weeds in cover crop plots

Adaptive N Management: Manure Management Cover Crop Selection

Corn Nitrogen Rate Optimization Following Fall Poultry Manure and a 13 Way Cover Crop

Mixture

Goals of the Study

• Determine if the addition of fall poultry manure and cover crops

could produce optimum yield with reduced nitrogen (N) inputs.

Cover Crop Planting

Seeding of 13 specie cover crop mixture that included buckwheat, oats,

cahaba vetch, sunflowers, sunn hemp, yellow blossom sweet clover,

crimson clover, sorghum-Sudan grass, purple top turnip, radish, cow peas,

pearl millet, and rapeseed.

Vertical tillage implement with

mounted air seeder. Cover crop

seed was broadcasted in front of

implement and then incorporated

into the soil.

Cover crop seeding- 8/12/16, Cover Crop sampling-04/10/2017, Cover Crop Biomass 1.4 ton/acre, Cover Crop N uptake= 42 lbs/ acre

11-3-16

N Fertilizer Management

N uptake and Corn Yield

Adaptive N Management: Cover Crop Selection

Impact of Cover Crop Species on Corn Yield

Decreasing amounts of CR result in decreasing differences in yield

0% CR 0% CR0% CR100% CR 80% CR10% CR

Thank You Questions?

Shalamar ArmstrongSoil Conservation and Management

Assistant Professor of AgronomyPurdue University Department of Agronomy

sarmstro@purdue.edu

https://ag.purdue.edu/agry/armstrong-sendlab/