Using Soil Respiration Tests to Measure Plant Available Nitrogen

in Cover Cropped Soils: Demonstrations, Research, & Outreach in

South Carolina

Arnold School of Public Health

Marlboro Soil and Water

Conservation

District

Chanda L. Cooper, Richland SWCDColumbia, South Carolina

Education Coordinatorcooperc@rcgov.us

Project TeamTechnical Director:

Dr. “Buz” Kloot

Project Management

Arnold School of Public Health

Marlboro Soil and Water

Conservation District

Conservation Innovation GrantSC-NRCS

Context

1. “You can’t build organic matter in Southeastern soils.”

2. Fertility recommendations based on conventional systems

Soil Test Debate in 1982

CIG Project Objectives: 1

Demonstrate and document the benefits of multi-species cover crops across a range of SC soils

CIG Project Objectives: 2

Demonstrate the use of the Haney-Brinton CO2 Burst Test and crop biomass samples to measure organic nitrogen

CIG Project Objectives: 3

Measure the impact of cover crops and reduced commercial fertilizer applications on crop yields and net operating costs

Project Field Locations

Dillon (3) Marlboro (1) Richland (1) 8-15 acre fields 58.9 acres (total)

Soil Characterization

Soil series, control points

Norfolk

Lynchburg

Soil Characterization

Topsoil color and structure Soil compaction

Maximum root depth Bulk density Penetrometer measurements

Multi-Species Cover Crops

Grass (1+) Rye, oats, barley

Legume (2+) Crimson clover,

Austrian winter pea, hairy vetch

Brassica (1+) Daikon/tillage radish,

purple top turnip, forage rape

October 31-March 15

Winter Cover CropsJanuary 6, 2014

Soil Testing to Measure Nitrogen Benefit

Biological Soil Testing, aka…

Soil Respiration Test

CO2 Burst Test Solvita (“soil

life”) Haney-Brinton

Test

Haney-Brinton CO2 Burst Test

Biomass Sampling

Y1: 500-9,500 lb/acre dry biomassY2: 850-8,400 lb/acre dry biomass

Commercial Nitrogen Reductions Based on Haney-Brinton Results

Norfolk

Lynchburg

Half of FieldStandard

Commercial Nitrogen

Application(as per standard

inorganic N recommendations)

Half of FieldReduced Commercial Nitrogen Application

(standard N recommendation minus plant available nitrogen

from cover crop, as indicated by CO2 Burst

Test)

Treatments

Ϯ winter peas – 3% N*Plus a check strip – 0 N

Field

Est Nmin (lb/ac)

Based on Soil CO2-C

Est N in Cover Crop

(lb/ac)

Crop

Standard N

Application (lb/ac)

Low N Application (lb/ac)

Carl ~40 ~170 Corn 120 65 (-55)

Jason ~40 ~190 Soybeans N/A N/A

Alan ~25 ~ 10 Corn 120 95 (-25)

John ~25 ~240Ϯ Milo 90 40 (-50)

Sonny ~25 ~270Ϯ Cotton 90 55* (-35)

Corn Crop2014

Expected Results

Reduced commercial nitrogen will not reduce crop yield while reducing operating costs

Soil health will improve Additional benefits:

Increased soil water-holding capacity; reduced runoff; temperature regulation; wildlife and pollinator benefits; IPM; etc.

Yield Results

Std N Low N Notes

Field 1 - Corn (bu/ac)

33 32 Poor rainfall

Field 2 - Soybeans N/A N/A No Std N/Low N difference

Field 3 - Corn (bu/ac)

183 126

Field 4 - Cotton (lb/ac)

1014 1143 Check strip (0 N) – 928 lb/ac!

Field 5 - Milo (bu/ac)

110 134

Soil Health Changes

OM increases 0.2%-0.6% per year

Soil pH steady (5.9-6.1) P, K steady without additions Reduced compaction; less

subsoilingOrangeburg loamy sand

(70-85% sand) after three years

of cover crops.

Granules ~5mm

diameter.

pH

Additional Benefits

Jason Carter has over $100/ac less in the CIG field in N and K fertilizer, herbicides and fungicides.

Outreach: Field Days & Workshops“If you don't believe soil health works, Imma take you out onto my fields so you can see for yourself!“

–Carl Coleman, Dillon County

Outreach:Media

YouTube

District Newsletters

South Carolina Wildlife Magazine

Newspape

rs

BlogsSocial Media

Join us on Facebook:

Carolina Cover Crop

Connectionhttps://www.facebook.com/groups/carolinacovercropconnection/

Join us on Facebook:

Carolina Cover Crop

Connectionhttps://www.facebook.com/groups/carolinacovercropconnection/

"Science is way behind the leading farmers

[when it comes to cover crops]“ –Dr. Ray Weil

Farmer-Led Research

Clio meeting New experiments

“Use check strips: they save us hundreds of thousands of dollars.” –Ray

Archuleta

Soil Health Movement

Practice (Farmers)

Science (Researchers

)

Outreach

(Communicators)

“During the past half century we’ve had an army of soil scientists telling us what our soils are. In just a few short years America’s soil health farmers have shown us what our soils can be. They’ve demonstrated the hope in healthy soil.” –Ron Nichols

Questions ?

Join us on Facebook:

Carolina Cover Crop

Connection

"The most powerful thing you can do for

the soil is plant a seed."

-Ray Archuleta