Detecting Yield Differences
From Alfalfa Plots of Various Widths
Bruce Anderson, Greg Cuomo,
and Mike Trammell
Department of Agronomy
University of Nebraska, Lincoln, NE 68583-0910
Alfalfa variety trials currently
are conducted with 2.5 to 8 foot plot widths
and yield collected from 38 to 100 percent of
the plot. Border effects influence yields of
adjacent plots in some plot studies. Many investigators
assume these effects are negligible in alfalfa
trials, possibly because plots are harvested
at nearly the same time and characteristics
like plant height do not appear to favor one
population over another. Thus, many alfalfa
variety trials have no side borders for their
plots, resulting in harvest of the entire plot
for yield. We examined the effect of various
plot widths on alfalfa variety yields and the
statistical ability to detect differences
among these varieties.
'Spredor II', 'Dawson', and
'Wrangler' alfalfa were seeded in 1988 near
Mead, NE in plots containing 5, 10, or 15
rows spaced six inches apart with twelve
inches between plots. Plot length was twelve
feet with a three foot border of alfalfa on
each end. Plots were arranged as a split-plot
in a RCBD with six replicates. A three-foot
wide strip was harvested from the center of
each plot using a flail harvester from nineteen
total harvests during five years. Thus, entire
5-row plots were harvested and alfalfa borders
remained on 10-row and 15-row plots.
Spredor II, Dawson, and Wrangler
yields averaged 5.40, 5.51, and 5.94 tons/acre
annually, similar to historical yields at
this location. Plot width did not affect
yields even though six or seven rows were
harvested from 10- and 15-row plots in
contrast to just five rows harvested from
the 5-row plots. Experiment wide variation
(C.V.) and ability to detect differences in
variety yields (F values) differed little
among plot widths (Table 1). Plots with borders
(10- and 15-rows) tended to have higher F values
when several years of data were combined. This
should result in greater ease in detecting
significant differences in yield, but sensitivity
analyses indicated there were no technique
differences (p >0.05).
Interactions of plot width and variety were
insignificant (Table 2), suggesting that
yield comparisons among varieties did not
change due to plot width.
To conclude, plots with 5 rows
spaced 6 inches apart and harvested with a
threefoot wide flail-type plot harvester
(commonly used for many alfalfa variety
yield trials) were as effective at comparing
yields of alfalfa varieties as wider plots
that left an alfalfa border following harvest,
indicating that plot width does not affect
alfalfa variety trials.
Table 1. F values and C.V.'s of alfalfa
variety yield tests using 5-row or 15-row plot widths.
|
| 5-row
|
| 15-row
| |
| Year
| F
| C.V.
| F
| C.V. |
| 1988
| 8.87
| 9.12
| 9.54
| 8.06 |
| 1989
| 1.84
| 7.52
| 0.60
| 6.72 |
| 1990
| 20.05
| 5.75
| 15.58
| 5.70 |
| 1991
| 2.06
| 6.29
| 2.13
| 7.30 |
| 1992
| 3.77
| 8.04
| 9.64
| 6.37 |
| 1989-1992
| 3.34
| 4.56
| 8.40
| 4.19 |
| 1988-1992
| 4.27
| 4.25
| 9.33
| 3.98 |
Table 2. Interactionsl of
plot width and variety.
| Year
| F value
| Pr > F |
| 1988
| 1.74
| 0.16 |
| 1989
| 0.71
| 0.59 |
| 1990
| 0.68
| 0.61 |
| 1991
| 0.50
| 0.74 |
| 1992
| 1.31
| 0.29 |
| 1989-1992
| 0.53
| 0.71 |
| 1988-1992
| 0.73
| 0.58 |
1Varieties differed (P<0.01)
except 1989; width never
differed (P>0.10) except 1988.
1995 Central Alfalfa Improvement Conference Proceedings
|