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YELLOW
NUTSEDGE GROWTH IN RESPONSE TO ENVIRONMENT
Corey
V. Ransom, Charles A. Rice, Joey K. Ishida, and Clinton C. Shock
Malheur
Experiment Station
Oregon
State University
Ontario,
OR, 2004
Introduction
Yellow nutsedge is a perennial weed
common in irrigated row crop production in the Treasure Valley of eastern
Oregon and southwestern Idaho. It is
particularly problematic in onion production.
Onions are relatively short statured plants with vertical leaves
producing an incomplete canopy with limited potential to effectively suppress
weeds. Yellow nutsedge has a C4
photosynthetic pathway and therefore responds well to conditions of high light
intensity that exist in onion production.
Management practices including frequent irrigation and high nitrogen
fertilization required to maximize onion yield also serve to stimulate yellow
nutsedge growth (Keeling et al. 1990).
Yellow nutsedge reproduces and is
dispersed primarily by tubers that are formed at the apical ends of
underground rhizomes. Tubers are
produced in the upper 18 inches of the soil profile with the greatest
concentration located in the upper 6 inches (Stoller and Sweet 1987, Tumbleson
and Kommedahl 1961). After a period of
dormancy, tubers germinate and produce shoots in subsequent growing
seasons. Tubers may remain viable for
1-3 years, providing an effective means of survival. Asexual reproduction by yellow nutsedge tubers can be quite
prolific. Tumbleson and Kommedahl
(1961) reported that a single tuber produced 6,900 tubers the first fall after
planting and 1,900 plants the following spring in an area of approximately 34ft2. Yellow nutsedge grows best where soil
moisture is high (Bendixin and Nandihalli 1987). Garg et al. (1967) reported that nitrogen promotes vegetative
growth over reproductive growth in yellow nutsedge, leading to increased basal
bulb formation (and subsequent shoot production) as opposed to tuber formation.
Two trials were conducted in 2004 at
the Malheur Experiment Station to evaluate yellow nutsedge growth with various
environmental factors.
Methods
Yellow nutsedge emergence and growth as
influenced by depth of germination
The objectives of this experiment were
to 1) determine the depth from which a yellow nutsedge tuber can emerge in the
field, 2) determine the date of emergence based on depth of burial, and 3)
determine the growth (i.e., shoot and tuber production) potential based on
burial depth.
Yellow nutsedge tubers were harvested
from a plot from the previous years irrigation trial on April 16, 2004. The tubers were washed from the soil, rinsed
with deionized water, and placed in a refrigerator at 38.5°F for approximately
14 days. Both washing and chilling have
been shown to effectively break tuber dormancy (Tumbleson and Kommedahl 1961,
Bell et al. 1962). This was necessary
to ensure that the tubers would readily germinate when buried and that any
differences in emergence would be based on depth of burial and/or soil
temperature and not differences in dormancy.
Ten tubers were buried in a single container at a selected depth of
either 2, 4, 6, 8, 10, 12, 14, 16, 18, or 24 inches on May 1. Each depth was replicated four times. Containers consisted of 10-inch-diameter pvc
pipe. Temperature sensors were placed
at 6, 12, 18, and 24 inches deep in 1 tube in each replication. Each container was irrigated by a single
drip emitter with an output of 0.5 gal/hr.
Watermark sensors (Irrometer Co. Inc., Riverside, CA) were buried 6
inches deep in every pot in the first and third replicate of the trial. Soil water potential was measured every
morning. Irrigations were initiated
each time the average of the Watermark sensors was greater than or equal to -20
kPa. Shoots were counted throughout the
season and shoots and tubers were harvested on July 7.
Yellow
nutsedge growth in response to irrigation and nitrogen fertilization
The objectives of this experiment were
to 1) monitor patch expansion from a single yellow nutsedge tuber in the
absence of crop competition over the course of one growing season, 2) evaluate
the effects of selected irrigation regimes on yellow nutsedge growth, and 3)
evaluate the effect of nitrogen fertilization on yellow nutsedge growth.
Tubers for this trial were harvested
from a ditch bank, were washed from the soil, rinsed with deionized water, and
stored in a refrigerator at 38.5°F for approximately 40 days. Tubers weighing from 0.18 to 0.2 g and
measuring between 6 and 7 mm were selected and planted in flats in the
greenhouse. Tubers of similar size and
weight were selected because research has shown that tuber size can affect
early plant vigor, with plants from smaller tubers being less vigorous. On June 4, a single germinated tuber with a
shoot of at least 1 inch long was transplanted into the center of each circular
plot of 6-ft diameter. Transplanted
yellow nutsedge plants were used to ensure a more uniform date of establishment
among the 18 individual plots. The
circular plots consisted of 14-inch-wide galvanized valley flashing cut to a
length of 19 ft with the ends riveted together to produce a circle with a
diameter of 6 ft. The flashing was then
buried approximately 10 inches deep in the soil. Prior to transplanting, each plot was drip irrigated to a soil
moisture potential of -20 kPa to incorporate fertilizer applications and to
provide similar moisture conditions for early yellow nutsedge establishment.
The trial consisted of 18 circular
plots, 6 each for the 3 irrigation regimes and 3 each for the 2 fertilization
levels split over the irrigation regimes.
Irrigation water was applied to the plots through 6 drip emitters evenly
spaced in a circular pattern, where each emitter was located 1.5 ft from the
center of the plot. The 6 emitters had
a combined output of 3.0 gal/hr. The
values for irrigation criteria were -20, -50, and -80 kPa and were selected to
represent soil moisture conditions similar to those in wheat, sugar beet, and
dry bulb onion production systems, respectively. The 2 fertilization levels consisted of plots receiving nitrogen
(N) (46 percent urea) at rates of either 90 or 268 lbs N/acre. All plots were fertilized before
transplanting with 90 lbs phophorus/acre, 90 lbs sulfur/acre, 1 lb copper/acre,
1 lbs boron/acre, and 9 lbs magnesium/acre.
Soil water potential was measured in each plot with a single Watermark
soil moisture sensor installed at a 6-inch depth equidistant from the yellow
nutsedge plant at the center of the plot and the drip line. Irrigation water was applied independently
for each regime when the average 6-inch soil water potential from the 6 sensors
reached either -20, -50, or -80 kPa.
The sensors were read by a datalogger every 3 hours, and once every 12
hours irrigation was initiated using a solenoid valve if the soil water
potential had exceeded the treatment criteria during the previous 12-hour
period. Water meters were installed
between the solenoid valves and the water line for each individual irrigation
regime to record the amount of water applied daily.
Yellow nutsedge growth was measured
initially by counting shoot numbers within each plot and by taking overhead
digital images of each plot. At a point
where shoots became too numerous to efficiently count, only overhead digital
images were taken of each plot. These
images were used to quantify the plot area that was covered by yellow nutsedge
shoots using a software program produced at Oregon State University (OSU). Shoots and tubers were harvested from
subsamples within each plot on September 29 and 30. Thirteen subsamples were collected across the 6-ft diameter of the
plots. The subsamples consisted of
4.25-inch-diameter circles from which shoots were counted to estimate the total
shoot number per plot. The shoots were
then clipped at ground level and placed in bags to be dried. The dry weights were used to estimate the
total above-ground biomass. Once the
shoots were removed, a soil core measuring 4.25 inches in diameter by 8 inches
in depth was taken from the same area where the shoots were removed. The individual core samples were bagged and
recorded as to their location within the plot.
The core samples were then emptied into a bucket with multiple
11/64-inch holes in the bottom and sides.
Water was sprayed into the bucket to remove the soil from the
tubers. The tubers were then counted
and weighed and those numbers were used to estimate the total tuber population
for each of the plots.
Results and
Discussion
Yellow nutsedge emergence and growth as
influenced by depth of germination
Plots where tubers were planted from 2
to 12 inches deep had an average of 1-5 shoots emerged on May 24, while deeper
depths had no shoots for another week or more (data not shown). The time required for treatments to produce
an average 5 shoots per plot ranged from 24 to 68 days after planting. The time required for 10 shoots per plot to
emerge ranged from 34 to 55 days for burial depths up to 18 inches. The tubers buried at the 24-inch depth
produced a maximum of 6 shoots at the time the plots were harvested. The average daily soil temperatures at 6,
12, 18, and 24 inches from planting through harvest are illustrated in Figure 1 and show that temperature extremes
are greatest nearer the soil surface.
If tubers were buried earlier in the year, we might expect to see
greater differences among emergence dates based on differences in the time
required for the soil at each depth to reach temperatures favorable for yellow
nutsedge germination. Figure 2 shows
the emergence of shoots as affected by planting depth from May 24 through June
7. At harvest, shoot numbers were
similar in plots where tubers were planted from 2 to 16 inches deep (Table
1). Tubers planted 18 and 24 inches
deep had fewer shoots than all other planting depths and the 24-inch depth had
the least number of shoots. The average
weight per shoot was less for 16-, 18-, or 24-inch depths compared to depths
from 2 to 12 inches (data not shown).
Tuber numbers were lower for plots where the planting depth was 14
inches or greater, with significant decreases as depth increased from 12 to 24
inches.
This research demonstrates that yellow
nutsedge shoot emergence is delayed at depths below 12 inches. Those shoots that emerge are fewer in number
and at depths below 16 inches are also smaller in size. This delay in emergence affects how many
tubers can be produced, and it is reasonable to expect that the delay in
emergence and reduction in individual shoot fitness would correlate with
reduced competitiveness from yellow nutsedge emerging from depths greater than
14 inches in the soil.
Table 1. Yellow nutsedge shoot emergence and shoot and tuber production as
influenced by depth of germination, Malheur Experiment Station, Oregon State
University, Ontario, OR, 2004.
|
|
Time to
emergence |
|
Yellow nutsedge production* |
||||
|
|
Average > 5
shoot/container |
|
Average > 10
shoot/container |
|
Shoots |
|
Tubers |
|
Depth of
burial |
|
|
|||||
|
|
--------- days after planting
----------- |
|
------------no/plot----------- |
||||
|
2-inch |
35 |
|
41 |
|
91 b |
|
250 b |
|
4-inch |
25 |
|
39 |
|
115 ab |
|
334 a |
|
6-inch |
24 |
|
34 |
|
101 ab |
|
333 a |
|
8-inch |
27 |
|
39 |
|
126 a |
|
313 ab |
|
10-inch |
27 |
|
39 |
|
108 ab |
|
240 b |
|
12-inch |
31 |
|
39 |
|
119 a |
|
272 ab |
|
14-inch |
39 |
|
40 |
|
119 a |
|
167 c |
|
16-inch |
39 |
|
45 |
|
108 ab |
|
97 cd |
|
18-inch |
45 |
|
55 |
|
66 c |
|
30 de |
|
24-inch |
68 |
|
> 68 |
|
6 d |
|
10 e |
*Yellow nutsedge
tubers were buried at the various depths on May 1, 2004, and yellow nutsedge
shoots and tubers were harvested on July 7, 2004. Data followed by the same
letter are not signficicant according to LSD (0.05).
Days after planting
for which the average of the 4
replicates for the given depth of
burial were greater than or equal to 5.
Days after planting for which the average of the 4
replicates for the given depth of
burial were greater than or equal to 10.
Figure 1. Average daily soil temperature at 6-, 12-, 18-, and 24- inch depths from yellow nutsedge tuber planting up to shoot and tuber harvest, Malheur Experiment Station, Oregon State University, Ontario, OR, 2004.
Figure
2. Yellow nutsedge
shoot emergence over time as influenced by depth of germination, Malheur
Experiment Station, Oregon State University, Ontario, OR, 2004.
Yellow nutsedge growth in response to irrigation and
nitrogen fertilization
There were no significant interactions
between irrigation criteria and fertilization.
Nitrogen fertilization did cause a significant increase in shoot number,
but not on shoot biomass, tuber number, total tuber weight per plot, or
individual shoot or tuber weight (data not shown). Since there were no interactions, irrigation criteria data were
averaged over fertilization levels.
Irrigation events and total water applied are shown in Table 2. The number of irrigations and the total
amount of water applied were much less for the
-20-kPa and 50-kPa irrigation treatments compared to 2003. This may have been because temperatures were
lower in 2004 compared to 2003. Soil
moisture potential over time by irrigation regime is illustrated in Figure 3. Irrigation had a significant effect on
yellow nutsedge shoot number and total weight (Table 3). The 20- kPa irrigation treatment produced
an average of 1,747 shoots per plot.
This was significantly greater than the 50-kPa and 80-kPa irrigation
treatments, which produced 444 and 411 shoots per plot, respectively. All shoot numbers were much lower than in
2003. The 50-kPa and 80-kPa
treatments produced similar numbers of shoots, while in 2003 the 50-kPa
treatment produced almost twice as many shoots as the 80-kPa treatment. The 20-kPa irrigation treatment produced an
average of 2.7 lb of shoot biomass per plot and the shoots in this treatment
had higher weight per shoot than in the other irrigation treatments. Based on the digital images, the area
infested by the yellow nutsedge shoots grew quickest for the 20-kPa treatment
and much slower with either the 50- or 80-kPa treatments (Fig. 4). Similar to 2003, the amount of area infested
was fairly small from June 4 to July 19.
Over a 27-day period from July 21 to August 17 the area infested by
yellow nutsedge in the 20-kPa treatments increased from 2.6 to 22.6 ft2. Yellow nutsedge tuber production was higher
with the 20-kPa irrigation criterion compared to the other irrigation criteria
and total numbers for this treatment were similar to 2003 (Table 4). An average of 19,508 tubers/plot were
produced from a single plant with the 20-kPa treatment. The 50- and 80-kPa treatments produced
4,447 and 5,826 tuber, respectively.
The 50-kPa treatment produced 10,000 fewer tubers in 2004 than in
2003.
This years results demonstrate that
under high levels of irrigation yellow nutsedge can produce large numbers of
shoots and tubers. This continues to be
much higher than previously reported in the literature. However, the differences between 2003 and
2004 suggest that factors other than irrigation criteria may significantly
affect the productive potential of yellow nutsedge when irrigation levels are
moderate.
Table 2. Number of
irrigations, amount applied per irrigation, and total water applied, Malheur
Experiment Station, Oregon State University, Ontario, OR, 2004.
|
Irrigation
criteria |
Irrigations |
Total
applied* |
|
|
kPa |
number/plot |
inches/event |
inches/plot |
|
-20 |
45 |
0.32 |
15.9 |
|
|
|
|
|
|
-50 |
7 |
1.0 |
8.5 |
|
|
|
|
|
|
-80 |
4 |
1.38 |
7.0 |
|
|
|
|
|
*Total includes 1.48 inch of rainfall.
