Long-term no-till research can provide valuable insights into crop production over many seasons. This research found that no-till soils generally had higher yields than tilled soils over time. No-till soils had cooler temperatures, held more water after rain, and had different soil biological properties and nutrient stratification compared to tilled soils. The impacts of no-till and fertilizer nitrogen on soil organic carbon and crop yields changed over the 50 years of the study.

2. Use of product names or labels does
not constitute endorsement by myself
or the University of Kentucky
John H. Grove
Professor, Plant and Soil Sciences Dep.
Director, University of Kentucky
Research and Education Center;
Princeton, Kentucky

3. Introduction
• No-till plant nutrition and yield?
• No-till soil properties and yield?
• Long-term research can inform us as
on a number of questions

4. Introduction
• Long-term research
– 5 years or more
• Why more valuable to us?
– Reflects what we do/who we are
• Crop production is a long-term
enterprise
– Need to ‘sample the seasons’

5. Department of Plant
and Soil Sciences
Soil Properties Can Drive Yield
• Over time, NT yields generally
greater
• Not due to a lack of N (or other
nutrients)
• Other soil properties dominate

6. Effect: p>F:
Till <0.05
N <0.001
Till x N <0.05
Effect: _ p>F:
Till <0.0001
N <0.0001
Till x N <0.01

7. 50
70
90
110
50 70 90 110
Average seasonal yield (bu/ac)
Treatmentyield(bu/ac)
TILL
NO-TILL
130
160
190
220
130 160 190 220
Average seasonal yield (bu/ac)
Treatmentyield(bu/ac)
TILL
NO-TILL
Wheat Corn
Corn generally likes no-tillage:
Wheat doesn’t always
average seasonal yield (bu/ac) average seasonal yield (bu/ac)

8. Department of Plant
and Soil Sciences
NT Soil Physics
• A. Generally cooler – all year long
• B. Generally wetter – after every rain
• A + B = C--> Generally higher heat
capacity (takes more energy, sunlight,
time to raise soil temperature 1 oF)
• D. Higher bulk density(?)
• B + D = E--> Generally lower oxygen (O2),
higher carbon dioxide (CO2) levels

9. Department of Plant
and Soil Sciences
Does Periodic Tillage (Once Every
Two Years) Influence Crop Yield?
Yes, but depends on the crop.
Seasonal yield responses - by crop
Till > NT Till = NT Till < NT
Wheat 4/10 5/10 1/10
DC Soybean 1/9 7/9 1/9
Corn 0/8 4/8 4/8

10. Department of Plant
and Soil Sciences
Pore Size Distribution
0.00
0.05
0.10
0.15
0.20
0.25
0.01 0.1 1 10 100 1000
Tension (MPa)
SWC(gg
-1
).
No Till
Till
Pore diameter (mm)
30 3 0.3 0.03 0.003 0.0003
0.00
0.05
0.10
0.15
0.20
0.25
0.01 0.1 1 10 100 1000
Tension (MPa)
SoilWaterContent(gg
-1
).`.
No Till
Till

11. Department of Plant
and Soil Sciences
Both have porosity, but which has structure?
Structure = functional utility.
Which better resists erosion? Compressive forces?
Chemical analysis would find no differences.
Structure adds value not measured by chemistry.

12. Department of Plant
and Soil Sciences
Thin Section of a Soil Aggregate

13. Department of Plant
and Soil Sciences
What’s A Little
Extra Porosity Worth?
• 2 to 4 days without wilting between
rainfall events!!

14. Effect: p>F:
Till <0.0001
N <0.0001
Till x N <0.7081

15. Department of Plant
and Soil Sciences
NT Nutrient Stratification
What’s the evidence?

16. Department of Plant
and Soil Sciences
Stratification of Mehlich III P
Average (both) = 20 ppm STP

17. Corn K Nutrition & Stratification
Blevins et al. (1986)
The vertical distribution of soil test K and K uptake by corn grown in two
tillage systems.
increment
soil test K
interval
soil test K
corn
K uptake
depth
increment
no-till
(NT)
plowed
(MP)
depth
interval
no-till
(NT)
plowed
(MP)
ratio
NT/MP year
ratio
NT/MP
inches ppm inches ppm
0 to 2 170 132 0 to 2 170 132 1.29 1980 1.35
2 to 6 104 113 0 to 6 126 119 1.06 1981 1.25
6 to 12 86 95 0 to 12 105 107 0.99 average 1.30

18. Department of Plant
and Soil Sciences
Corn Yield Response to P Availability and Stratification
0
20
40
60
80
100
120
140
160
180
0 5 10 15 20 25
Average Soil Test P (lb/acre)
Yield(bu/acre)
stratified
not stratified

19. Department of Plant
and Soil Sciences
2400
2600
2800
3000
3200
LS HS
GrainYield(bu/acre)
S0 S1
39.5
43.7
45.7
43.5
Soybean response to No (S0) or Yes (S1)
Starter P at Low (LS) or High (HS) P
Stratification

20. Department of Plant
and Soil Sciences
P Applied-Removal and Soil Test P at 92 P2O5/acre
0
50
100
150
200
250
1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
Year
SoilP(lbP/acre)
Soil Test P 0 to 3
Soil Test P 3 to 6
Cumulative P Applied
Cumulative P Removed
8.2 lb P2O5/lb STP
Soil P Dynamics @ 92 lb P2O5/A
92 lb P2O5/A
= 40 lb P/A
Fertilizer P applied once every two years (ahead of corn planting).

21. Department of Plant
and Soil Sciences
The lb P2O5/A
required to change
MIII soil test P
(STP) by 1 lb/A – as
related to the initial
soil test P level –
after an 8 week lab
incubation of mixed
(tilled) soil.
Thom and Dollarhide, 1987
12 lb P2O5 per lb
STP => 30% lower
fixation in NT soil

22. Department of Plant
and Soil Sciences
If You Don’t Mix It,
You Don’t Fix It

23. Department of Plant
and Soil Sciences
If Stratification Is Such
A “Good Thing” In NT, When Do You
Need The Most Nutrient Management?

24. Avoiding Losses:
Immobilization, Leaching,
Denitrification, Volatilization
Nitrogen

25. Department of Plant
and Soil Sciences
Nitrogen
Avoiding Losses: Immobilization,
Leaching, Denitrification,
Volatilization

26. Department of Plant
and Soil Sciences
NT’s Soil Nitrogen Biology
• Larger biological community; more
stratified;
• Shift towards more anaerobic, less
aerobic (less oxidative, more reductive)
• Slower aggregate turnover
• Faster N immobilization, denitrification,
volatilization; slower N mineralization,
nitrification

27. Department of Plant
and Soil Sciences

28. Department of Plant
and Soil Sciences
N Grain
N Rate Yield
Source lb N/A bu/A
control 0 116d
UAN 80 189c
UAN + Instinct 80 204bc
UAN 120 218b
UAN + Instinct 120 241a
Corn Yield - 2009
Schwab

29. Department of Plant
and Soil Sciences
Take-Home on N
Inhibitors/Stabilizers
• Inhibitors are needed on some fields in
all years; more fields in some years
• Know the field, know the situation, know
the season
• There are alternatives (placement,
split/delayed application) to the N
inhibitors, enhancers – may be cheaper,
doable (or not)

30. Soil C and N:
How Much Difference Due To
Tillage And Fertilizer N?

31. Department of Plant
and Soil Sciences
Corn Yield to Applied & Residual N
from Organic Matter and Tillage

32. Objectives
• Examine the role of fertilizer N in
SOC accumulation/loss.
• Understand the SOC status of
managed cropland relative to
unmanaged grassland.
• Determine the role of tillage in SOC
accumulation/loss, especially at depth.

33. Measure Soil Organic
Matter (as SOC) After 38
Years: By Depth And For
The Whole Root Zone

34. Long-Term Tillage-N Trial
• Continuous corn, with a winter cereal
cover crop.
• Initiated in spring 1970 into a bluegrass
(Poa pratensis L.) pasture.
• No-till (NT) and moldboard plow (MP)
tillage, with 0, 75, 150 and 300 lb N/A
as 34-0-0.
• Deep, well-drained Maury silt loam near
Lexington, KY

35. Design and Execution
• Soil sampled 0, 150 and 300 lb N/A
rate treatments, in both no-till (NT)
and moldboard plow (MP) tillage
treatments, in April, 2008.
• Took 3 cores per plot, to a depth of 1
m, in 10 cm (4 inch) increments.
• Determined soil bulk density (BD), total
N (TN) and organic carbon (SOC).
• Soil sampled nearby sod at 4 corner
locations.

36. ****
**
****
**
*

37. ****
****
**
**
*

38. Tillage, N and SOC
• At all N rates, MP resulted in greater
SOC uniformity throughout upper 30
cm and a pronounced SOC ‘bulge’ at 30
to 40 cm.
• NT profile SOC distribution similar to
that for the grass sod.
• Relative to the unfertilized grass sod,
unfertilized crop land SOC differences
(25% less) were confined to the
surface 50 cm of both MP and NT soils.

39. And When All Depths
Are Added Up?

41. Tillage, N and SOC
• Without added N, SOC change due to
agroecosystem change (grassland sod to
continuous corn) was not affected by
tillage, falling equally low.
• MP tillage is a major oxidative force,
especially at greater N rates that
would otherwise promote greater SOC
retention. Greater N gives ‘opportunity’
for SOC formation with cover crop/NT.

42. Tillage and Fertilizer N:
Temporal Change in Corn Yield
Response

43. Long-Term Tillage-N Trial
• Continuous corn, with a winter cereal
cover crop, for 50 yr (1970 to 2019).
• Initiated in spring 1970 into a bluegrass
(Poa pratensis L.) pasture.
• No-till (NT) and moldboard plow (MP)
tillage, with 0, 75, 150 and 300 lb N/A
as 34-0-0.
• Deep, well-drained Maury silt loam near
Lexington, KY

44. Spring, 1970: Start With A
50+ Yr-Old Pasture/Sod

45. 50-Year Trial Execution
• Tillage and burn-down herbicide
treatments imposed middle April.
– Moldboard plowed 8 to 10 inches deep 1-2
weeks prior to planting
– Disk harrowed 3 t 4 inches deep
• Corn planted late April to mid-May.
• Ammonium nitrate applied within a week
of planting.

46. 50-Year Trial Execution
• Weed control:
– burndown + pre-emerge
– post-emerge (usually twice)
• Fungicide & Insecticide – seed
treatment only
• Hand harvested late September to early
October.
• Winter cereal (rye, wheat, triticale)
cover crop established post-harvest

47. Introduction
We do long-term
experiments, not just
because we expect there to
be a simple effect of time,
but because we think there
might be an interaction
between time and one or
more treatments or
treatment combinations.

48. Introduction
The impact of time has random and
non-random components:
Continuous application of
input/treatment
One application of fertilizer N each
year; one tillage sequence per year
‘Seasonality’ of crop response
In rainfed agriculture, crop response
to N varies with moisture
availability/stress

49. Assumptions, Going Forward
 Other management changes captured ‘over time’:
 cultivar selection
 row spacing and plant population
 planting date
 herbicide selection
 rye establishment method
 pH/nutrient management.
 50 years adequately represents the “population”
of seasons.
 Average annual experiment yield (annual grand
mean) adequately represents “seasonal quality”.

50. Corn Yield Results

51. Partitioning the Variability in
50 yr of Corn Grain Yield
Source of variance
Proportion of
total variance %
Probability of a
greater F value
year 42.44 < 0.0001
block 0.85 <0.0001
tillage 0.36 <0.0001
year*tillage 2.36 < 0.0001
N rate 33.76 < 0.0001
year*N rate 12.74 < 0.0001
tillage*N rate 0.05 0.0036
year*tillage*N rate 1.33 < 0.0001
McIntosh (1983) Agron. J. 75:153

52. Effect: _ p>F:
Till <0.0001
N <0.0001
Till x N <0.0001

53. Effect: p>F:
Till <0.0001
N <0.0001
Till x N <0.0062

54. Effect: p>F:
Till <0.0001
N <0.0001
Till x N <0.0085

55. Effect: p>F:
Till <0.0001
N <0.0001
Till x N <0.0791

56. Effect: p>F:
Till <0.0001
N <0.0001
Till x N <0.7081

57. Less Lumping:
More Splitting

58. Separating Annual Trend
From Seasonal Behavior

64. Historical Tillage Response Depends on N:

65. Historical Tillage Response Depends on N:

66. Historical N Response
Depends on Tillage:

67. Conclusions
• Character of the tillage by N rate
interaction on corn yield profoundly
changed with time.
• NT corn environment more favorable for
improved yield potential with better
genetics and management – more water.

68. AfterBefore