Vol. 51—1997 - NorthEastern Weed Science Society

3
MATERIALSANDMETHODS
Experiments w~re run in sections of oat production fields near Aurora, NY in 1992, 1994and
1995. Consequently, all field operations other than cultivationwere carried out as part of a
typical production process. Experimentdesign was a randomizedcomplete block with four
replications of four treatments. Soil in all fields was a moderately well drained silt loam (fineloamy,
mixed, mesicGlossoboric Hapludalt). The oat variety was 'Ogle' in 1992 and 'Newdak'
in 1994 and 1995. IFertilizerwas banded at planting: 336 kg/ha of 15:15:15in 1992,280 kg/ha
of 15:15:15 in 1991and 183kg/ha of 10:20:20in 1995. Plots were 4.6 m by 30 m except for the
2,4-0 treatment which was 9.2 m by 30 m to accommodatethe sprayer. Due to wet weather,
planting date was l~te in 1992,somewhatlate in 1994,but typical for the region in 1995 (Table
1). .
Table 1. Dates of ~eld operations and data collection in 1992, 1994 and 1995.
Planting
First cultivation
I
Second cultivationl i
Stand count
2,4-0 application II
Weed biomass
Harvest
I
I
1992
8 May
16May
23 May
26 May
16June
16-20Iuly
9 Aug.
1994
28 Apr.
3 May
20 May
27 May
Ifl June
21-29 July
10Aug.
1995
17 Apr.
24 Apr.
9 May
22 May
19 May
12-17July
7 Aug.
We cultivated with the tine weeder and rotary hoe before crop emergence and again at the 2-
3 leaf stage (Tablell). In 1992we used a John Deere series 400rotary hoe, and in 1994 and
1995 an M&W Gear model 1815MTrotary hoe. The tine weeder was a Lely model 450 in all
years. Driving sJXtedSwere 12 to 15 kmph for the rotary hoe, and 4 to 8 kmph for the tine
weeder. Working [depthwas 2.5 to 4 cm in all operations. Dimethylaminesalt of 2,4-0 was
applied at 0.54,0.$4 and 0.43 kg a.i./ha in 1992, 1994and 1995in 140Jlhaof water with a boom
sprayer equipped 'fvithflat fan nozzles.
Crop density Jas evaluated 1 to 2 weeks after the second cultivationby counting oat plants
in two randomly l~ated 2 m sections of row in each plot (Table 1). Above ground weed
biomass was determined in mid Iuly (fable 1) by clipping four randomly located quadrats per
plot. Quadrat size was 0.25 m 2 in 1992,but was increased to 0.5 m 2 in 1994and 1995when
weed biomass wa~ lower. Weeds were clipped near ground level and sorted into annual
broadleafs, perennial broadleafs, annual graminoidsand perennial graminoids. Broadleafs and
graminoids were ~ombined for reporting as this caused little loss of information. To avoid
effects of trampling on yield, crop stand counts and weed biomass clipping avoided the central 2
m of each plot We determined yield by harvesting the center 1.2 m strip with a plot combine.
The grain receiv~ an additional cleaning, and yields were adjusted to 13.5%moisture for
reporting. I
All data were ~ubjected to analysis of variance. Weed biomass data were transformed to
logarithms prior t~ analysis to stabilize variance. We used predefined,single-degree-of-freedom
orthogonal contraits to separate treatmenteffects.