1997 Ornamentals Research Report - AUrora - Auburn University

44
ALABAMA AGRICULTURAL EXPERIMENT STATION
increased with two of the four species (Table 2). With the pellets
all four species decreased in shoot dry weight with an increase
in mulch depth. Ageratum exhibited the greatest shoot dry
weight inhibition. Compared to the control plants, ageratum
shoot dry weight was 55%, 78%, and 93% less with crumble
mulch treatments of 0.5-, 1.0-, and 2.0-inch depth. Ageratum
grown in pellet mulch treatments followed a similar trend to
crumble mulch treatments. The three treatments representing
industry standards (pine bark mulch, pine bark mulch with
weedmat, and Ronstar herbicide) also reduced ageratum shoot
dry weight, with the Ronstar herbicide treatment causing the
least suppression. These data indicate all mulch treatments
Table 3. Experiment 2: Influence of Mulch Type
and P Level on Growth of Annual Species'
Treatment 2 P level
Ageratum
Shoot dry weight
Geranium Marigold
Crumble
Crumble
Crumble
Pellet
Pellet
Pellet
PB+m
ppm
0.0
3.75
7.5
0.0
3.75
7.5
g/plant
6.3
19.0
12.8
5.5
12.2
10.5
g/plant
9.6
9.8
13.2
7.5
9.7
I11.0
g/plant
36.5
36.6
32.2
37.7
33.0
34.5
3 PB
Ronstar
0.0
0.0
10.4
8.8
9.6
8.3
32.7
36.4
4 Control
0.0 10.7 10.5 40.7
s 44 ALABAMAAGRICULTURAL EXPERIMENT STATION
ageratum growth 121% and 90% compared to no-P plants. The
addition of P did not affect the growth of geraniums or
marigolds. (Table 3). These data are consistent with the first
study where ageratum was the most sensitive to recycled paper
mulches and the other species were less affected at the one-inch
depth. Growth index again followed a similar trend to shoot
growth data.
Root dry weight of ageratum increased with both levels
of P, with the crumble at 3.75 ppm P producing the best growth.
Geranium was not affected by the addition of P, but the highest
dry weight was produced with the 7.5 ppm with the crumble.
Marigold growth was not affected by the addition of P (Table 3).
Ageratum plants grown in the plots with recycled paper
treatments exhibited a varying response in the root volume
displacement test. The crumble at 3.75 ppm produced the
best growth, which was equal to the pinebark plus
weedmat. Geranium root volume increased linearly in the
paper crumble mulch, but not with the pellets. Mulched
0.0 12.5 8.5 39.2
plots in general showed better root growth than unmulched
plots. Marigolds did not benefit from the addition of P and
decreased in root volume with additional P.
All mulch treatments provided effective weed
control (90% plus) (Table 4). Ronstar provided about
80% weed control at 45 DAT. Weed dry weight was less
for all mulch treatments compared to the Ronstar-treated
plot and the nontreated control. For example, weed dry
weight for any paper treatment did not exceed 0.85
2'Experiment 2 terminated 45 DAT (Sept. 13 - Oct. 30).
All recycled newspaper mulch applied at one inch depth.
3Pinebark plus Geogard weedmat.
4Ronstar applied at four pounds active ingredient per acre.
5No mulch applied.
grams per plot, whereas Ronstar plots had 7.6 grams per
plot and the control, 30.2 grams per plot.
These data show paper mulches to be effective in
controlling weeds, as well as conserving moisture.
Addition of P overcame the negative affects of aluminum in
some species, but not in all species. Based on the response to
the newspaper treatments, ageratum could serve as an
indicator species for plant interactions with the paper.
reduced ageratum shoot dry weight. With marigold, shoot dry
weights were similar among the three industry standard
treatments and pelleted recycled newspaper at depths of 0.5 and
one inch.
At termination, the plants were dug and the roots
examined. Roots in those plots receiving one or two inches of
newspaper mulch exhibited a disruption of root growth. Root
systems were stunted and lacking in fine branching.
By 46 DAT all mulched plots had higher moisture
levels than the unmulched plots, and all paper treatments with
the exception of pellets at 0.5 inch were different from the
control (Table 1). Generally the paper mulches had slightly
increased or similar moisture levels between the 32 and 46
DAT readings, whereas the unmulched plots had a decrease in
moisture levels.
EXPERIMENT 2. When no P was added to the
newspaper products, ageratum growth was about half that of
the control plants. Addition of P at 3.75 and 7.5 ppm to
crumble paper increased ageratum growth 200% and 103%
respectively compared to no-P crumble mulched plants.
Addition of P at 3.75 and 7.5 ppm to pelleted paper increased
Table 4. Experiment 2:Weed Control and Weed
Dry Weight After Various Mulch Treatments
Treatments' P level Weed control
20 DAT
Weed dry weight
2 45 DAT (45 DAT)
ppm pct. pct. giplot
Crumble
Crumble
0.0
3.75
98.5
98.5
97.3
93.8
0.4
0.9
Crumble
Pellet
Pellet
7.5
0.0
3.75
99.0
98.0
99.0
96.0
97.8
98.0
0.4
0.4
0.2
Pellet
PB+m
7.5 98.5 97.8 0.7
3
PB
Ronstar
0.0
0.0
100
94.8
99.5
90.3
0.0
1.8
4
Control
0.0 81.3 78.8 7.6
s
0.0 58.8 52.5 30.2
'All recycled newspaper mulch applied at one inch depth.
2 Days after transplant.
3Pinebark plus Geogard weedmat.
4 Ronstar applied at four pounds active ingredient per acre.
SNo mulch applied.