Deep tillage:
Needed or not?

Joseph L. Pikul Jr.

Soil Scientist

USDA-ARS

Brookings, SD

Presentation direction

n Introduction

n Tillage and soil organic matter

n Old studies, what was discovered?

n New studies, what is being discovered and rediscovered in and outside the North Central Region

n Other considerations

n Conclusions

Interpretation of tillage terminology requires caution (Glossary of Soil Science provides 119 terms to describe tillage)

Example of “strip till”:

n Rawson system (zone building): named after Michigan farmer Ray Rawson

n No till plus (1970’s): a term coined by implement dealers in the SE Coastal Plains to describe the use of subsoiling at planting to break “root-impeding layers”

n Strip tillage

n Zone tillage

n In-row subsoiling

Why deep tillage?

n Fracture compacted soil

n Improve water infiltration

n Decrease runoff and soil erosion

n Increase crop yield

n Tillage feels good

n Own the equipment so use it

n Snake oil sales

Management & organic matter: Conclusions form 67 long-term experiments

n A change in tillage from CT to NT increased C sequestration (excluding wheat-fallow).

n  A new SOC equilibrium in 15-20 yr

n An increase in rotation complexity increased C sequestration (excluding a change from continuous corn to corn-soy).

n  A new SOC equilibrium in 40-60 yr

Deep tillage in the 30’s…..

1952, Minnesota Farm and Home Science

“You don’t gain with deep tillage”

 by A.J. Schwantes, et al.

Findings (1933-1939):

n Yields were not different between deep-tilled (vertical chisel operated between 12”-15”deep) and plowed

n Deep-tilled soil did not hold water any better than plowed

n Deep-tillage costs more than plowing

n No difference between stations (soil type)

n Duluth

n Grand Rapids

n Crookston

Deep tillage in the 50’s…

1960, Agronomy Journal

“Effect of subsoiling….. on yields of corn”

 by W.E. Larson, et al.

Findings (1955-1957):

“Subsoiling has considerable appeal to farmers, but research has shown few benefits in the North Central United States”

n Subsoiling to 16 - 24 inches did not increase corn yield in Iowa

n Subsoiling to 12 - 18 inches produced a significant yield response in only 2 of 14 field experiments.

Effect of deep tillage on crop yield: Literature review

Parting thought on past research and a question for the present:

n Past: in most cases deep tillage did not improve yield

n Present: strip tillage, important for wet cold soils (good idea)

n Controls traffic

n helps warm soil, most surface residue remains

n precisely apply some N in fall (fertilizer knives)

n Less energy used than full-field tillage

n Does it make good sense to couple deep tillage with strip tillage (commonly called zone building)?

5 recent field studies involving deep tillage

n Corn yield on a silt loam soil, about 4 miles east of Rochester, Minnesota (1997-2000)

n Corn and soybean yield on a silty clay loam: Monsanto Farm near Newton, Iowa

n Sugarbeet on a Fargo silty clay (smectite = high shrink swell) and Glyndon silt loam

n Irrigated corn on a loamy sand near Florence, South Carolina

n Spring wheat production in eastern Montana

Corn yield following corn or soybean
 Olmsted County, MN (1997-2000)

Corn and soybean yield
Monsanto Farm, Newton, IA (2002)

Sugarbeet yield on Fargo silty clay and Glyndon silt loam (1992-1993)

Florence, SC: Irrigated corn yield on a loamy sand (1979-1981)

Sidney, MT: Annual spring wheat yield under no tillage (AWNT) and fall-spring tillage (AWFST)

Sidney MT: an attempt to improve spring wheat yield by fracturing tillage pans…….

Wheat yield on a sandy loam near Culbertson, MT (1993-1995)

Additional aspects of tillage…..
How do the pieces fit?
some speculation…….

n Frozen soil

n Economics of tillage

n Nature (time) heals

Fall tillage to improve water infiltration into frozen soil

Cumulative water infiltration into soil that was ripped (R) and not ripped (NR)
Sandy loam, Culbertson, MT

Natural amelioration of compacted soil: Truth or rural legend ?

The Wadsworth Trail (1864-1871) Stevens County, Minnesota

Subsoil compaction: Lamberton and Waseca, Minnesota

Natural recovery of severely compacted soil at 19 military training sites: