Download Sulfur for Kentucky Grain Crops: A Meta

Sulfur for Kentucky Grain Crops:
A Meta-Analysis
John H. Grove
University of Kentucky
Department of Plant
and Soil Sciences
John H. Grove
University of Kentucky
Objectives
What is the evidence of S need in
Kentucky’s corn, soybean and wheat?
Controversial, but lots of recent work
The 3-4 rep field trials not definitive
Use meta-analysis:
Explore this alternative approach to
data aggregation
Department of Plant
and Soil Sciences
Outline
Definition(s) of meta-analysis
Agricultural meta-analysis examples
interpretation strengths/weaknesses
Grain crop response to S in Kentucky
interpretation strengths/weaknesses
Conclusions
Department of Plant
and Soil Sciences
Defining Meta-Analysis
“meta-”
along with; after; beyond; transcending;
higher
“meta-analysis”, the analysis of analyses
methods focused on contrasting and
combining results from different studies
more powerfully estimate the true effect
size as opposed to a less precise effect
size derived in a single study under a given
single set of assumptions and conditions
Webster’s Dictionary; Wikipedia
Department of Plant
and Soil Sciences
Advantages of Meta-Analysis
Combines several studies – can be less
influenced by local bias;
Shows whether the results are more
varied than what is expected from the
sample diversity;
Is a generalization to the population of
studies (the inference space);
Has higher statistical power to detect
an effect than individual studies.
Wikipedia
Department of Plant
and Soil Sciences
Disadvantages of Meta-Analysis
Publication bias – file drawer problem;
When a practice or product shows no
effect you get under-reporting.
Agenda-driven bias – cherry picking;
The meta-analyzer might find reasons to
exclude, rather than include (or explain).
Inference space “is like beauty”;
Meta-analysis expands inference space
Meta-analysis dilutes inference space
Department of Plant
and Soil Sciences
A Meta-Analysis Example
“Plant health” (corn fungicide use) is
scientifically controversial – results from
individual trials “all over the place”.
12 Land Grant plant pathologists pull
together response data from 212 ‘valid’
studies conducted in 14 states.
Determine the average yield difference to
fungicide use for each study.
Arrange the yield difference data from
most negative to most positive.
Department of Plant
and Soil Sciences
151 studies with Headline®
individual study difference
individual study standard error
mean difference = 4.1 bu/A
standard error = ± 0.6 bu/A
significant at the 99.9% level of confidence
Paul et al, 2011, Phytopathology 101:1122-1132
Department of Plant
and Soil Sciences
Other Summary Comments
Mean yield difference was greater:
On fields with lowest non-treated yields;
On fields with higher disease severity.
“Use of these foliar fungicides is unlikely
to be profitable when foliar disease severity
is low and yield expectation is high”.
Paul et al, 2011, Phytopathology 101:1122-1132
Department of Plant
and Soil Sciences
Another Meta-Analysis Example
Wadsworth (1987) conducted an
experiment on a range of crops, over
several years (66 studies).
Did, or did not, add a small amount
(24 gallon per acre) of water.
No expected benefit to this small
amount of water.
Yield difference expressed as a
percentage of the control.
Department of Plant
and Soil Sciences
Response Range Was -22% to +33%
100%
Cummulative distribution (%)
Greatest response
75%
50% responses above zero
Average response
(-0.6% 2.3%)
50%
25%
50% responses below zero
Lowest response
0%
-40
Department of Plant
and Soil Sciences
0
40
80
Response to water (%)
120
160
Cumulative Distribution (%)
100%
75%
Fertiliser
Phosphorus
50%
Fertiliser N
Products that raise
yield move curve to
the right
25%
0%
-40
0
40
Response to Product (%)
Department of Plant
and Soil Sciences
80
120
160
Do Kentucky Soils Need S?
Electric power: by-product gypsum (FGD)
New company converts FGD dust to
pelletized product for bulk blending
Commissioner of Agriculture (recently elected
and with gubernatorial aspirations) publicly
linked to new company – states that there is
general need for S in Kentucky soils
Fertilizer retailers want new products
Ag reporters for state’s 2 major
newspapers ask UKAg about need for S:
Department of Plant
and Soil Sciences
Do Kentucky Soils Need S?
UKAg response is a quiet, but firm No
Reporters return to Commissioner of
Agriculture: Reply lacks perspective
Fertilizer retailers worry: UKAg
extension commands respect
Grain growers desire general evaluation:
Know many field trials have been done
UKAg Dean commissions meta-analysis
Department of Plant
and Soil Sciences
Grain Crop S Nutrition Meta-Analysis
Between 2008 and 2012, 72 valid
comparisons, within 34 field trials, that
involved a –S control and a +S treatment
valid = 3 or more replications per treatment
40-corn, 23-soybean, 9-wheat
11 counties spread widely across the
state; mostly NT soil management
+S rate ranged from 8.4 to 1230 kg S/ha
Koch-Agrotain and Mosaic-MES product
evaluation trials of particular value
Department of Plant
and Soil Sciences
Grain Crop S Nutrition Meta-Analysis
S sources were gypsum (CaSO4.2H2O);
ammonium sulfate ([NH4]2SO4); or MES
(10-40-0-10S)
Wide yield (Mg/ha) range: 4.6-17.5 (corn),
1.1-4.8 (soybean), and 4.6-6.9 (wheat)
+S response, as % of the –S check, ranged
from -22.4% to +18.3%; mean of +0.11%
No significant difference (probability of a
greater F > 0.10) in any single study or
when all grain species combined together
Department of Plant
and Soil Sciences
Frequency of S Response - All Comparisons/Crops/Location-Years
Cumulative Frequency (%)
100
50
0
-25
-20
-15
-10
-5
0
5
+S Response (%)
Department of Plant
and Soil Sciences
10
15
20
25
Numerical Evaluations
72 Grain Crop Comparisons
Mean response to added S: + 0.11 %; not
statistically different from 0%
Median response to added S: +1.12 %; not
statistically different from 0%
40 Corn Comparisons
Mean response to added S: - 0.71 %; not
statistically different from 0%
Median response to added S: +0.57 %; not
statistically different from 0%
Department of Plant
and Soil Sciences
Numerical Evaluations
23 Soybean Crop Comparisons
Mean response to added S: + 0.54 %; not
statistically different from 0%
Median response to added S: +0.82 %; not
statistically different from 0%
9 Wheat Comparisons
Mean response to added S: + 2.61 %; was
statistically different from 0%
Median response to added S: +1.77 %; not
statistically different from 0%
Department of Plant
and Soil Sciences
Other Numerical Evaluations
Soil Order: Alfisols, Mollisols-Inceptisols,
Ultisols; not different from 0.0 %.
Year: 2008, 2009, 2010, 2011, 2012; not
different from 0.0 %.
Soil Drainage: well-drained, moderately
well-drained, somewhat poorly/poorly
drained; not different from 0.0 %.
Fragipan: absence, presence; not
different from 0.0 %.
Department of Plant
and Soil Sciences
Department of Plant
and Soil Sciences
Conclusions
No relationship of S response to yield,
for any crop
The data, from individual or aggregated
experiments, do not support a general
grain crop S recommendation
There is no evidence of a need to begin
field trials with the intent of developing an
S fertilizer recommendation for Kentucky
grain crops
Department of Plant
and Soil Sciences
Acknowledgements
Dr. Greg Schwab (now with Koch
Agronomic Services, LLC) and Dr.
Edwin Ritchey for contributed data
Dr. Eugenia Pena-Yewtukhiw (West
Virginia University) for assistance
with the meta-analysis
Department of Plant
and Soil Sciences
Thank You!
Questions?