Monday, September 22, 2014
Wednesday, August 13, 2014
Wednesday, July 2, 2014
Comments on a Recent Visit to the Virginia Beach Microclover Demonstration Trials
Last week I had the opportunity to participate in the Virginia
Tech Turfgass Field Day at the Hampton Roads Agricultural Research and
Extension Center in Virginia Beach. Over the last two years project members Dr.
Jeffery Derr, Dr. Mike Goatley and Turfgrass specialist Adam Nichols have been examining
the establishment of a microclover bermudagrass lawn from seed, and the practice
of overseeding microclover into an existing stand of bermudagrass. In both trials they are also looking at the
effect of compost addition on the presence of microclover in bermudagrass.
It is likely that the enhanced availability of nutrients associated with the incorporation of compost (i.e., mostly nitrogen) favors bermudagrass growth and establishment over that of microclover. Dr. Derr also noticed that there was much less weed competition within the compost amended plots compared to the non-amended plots during establishment. The reduced level of weed competition in these plots may have also favored bermudagrass establishment over microclover establishment. Microclover and regular old white clover are present throughout the plots that were not amended with compost. This reinforces my belief that the lack of clover cover seen in the compost amended plots is primary due to the enhanced availability of nitrogen in these plots.
In the case of the establishment trial, the soil was either
amended with two inches of yard waste compost or was left un-amended prior to seeding with 2 pounds per thousand
square feet of Yukon bermudagrass, or
alternatively, the same bermudagrass variety containing 5% by weight
microclover . In the case of microclover overseeding trial, one-quarter inch of
compost was applied as a topdressing immediately after seeding and once a year
thereafter. Plots not receiving compost topdressing treatment have received
urea at yearly rate of one pound of nitrogen per thousand square feet. The
establishment trial was initiated in July 2012 and the microclover overseeding trial
in September of 2012. The microclover seeding rate in the overseeding study was
two pounds of microclover seed per thousand square feet.
Jeff has been sending me regular updates on color, quality
and amount of clover present in each of the plots, however I did not grasp how
stark the difference in treatments have been until seeing the two trials this
past week. In brief, amending the soil with 2 inches of compost dramatically suppressed
the presence of clover in the bermudagrass at this site. As can be seen in the
first picture below there is very little
clover in a compost amendment plot that was seeded with the 95% bermudagrass,
5% microclover seed mixture. The amount of clover present in this plot is indistinguishable
from that of a nearby compost amended plot seeded with 100% bermudagrass at the
same time (lower picture).
Compost amended plot seeded with 95% bermudagrass, 5%
microclover seed mixture two years ago.
Compost amended plot seeded with 100% bermudagrass two years
ago.
It is likely that the enhanced availability of nutrients associated with the incorporation of compost (i.e., mostly nitrogen) favors bermudagrass growth and establishment over that of microclover. Dr. Derr also noticed that there was much less weed competition within the compost amended plots compared to the non-amended plots during establishment. The reduced level of weed competition in these plots may have also favored bermudagrass establishment over microclover establishment. Microclover and regular old white clover are present throughout the plots that were not amended with compost. This reinforces my belief that the lack of clover cover seen in the compost amended plots is primary due to the enhanced availability of nitrogen in these plots.
What stood out to me when viewing the overseeding trail
was that in plots overseeded with microclover but not topdressed with
compost, the presence of the microclover resulted in a darker colored turf than
in plots that were devoid of microclover. At this field station stop however Adam Nichols was quick to
point out that the primary difficulty with overseeding microclover into
bermudagrass is the inability in obtaining a homogenous mixture of the two
species. The appearance of the plots overseeded with microclover (with or
without the compost topdressing treatment) could best be described as “a patchy
mosaic” of microclover within the plot. If the approach of using microclover to
reduce lawn fertilizer use in bermudagrass is ever to gain favor, it appears
that obtaining something close to an homogenous stand of the two species will
require more than a onetime overseeding of microclover into bermudagrass.
Labeled plot in foreground was overseeded with
microclover 21 months earlier while labeled plot in background was not. The annual
amount of fertilizer applied to both plots is one pound of urea nitrogen per
thousand square feet.
Thursday, June 26, 2014
Your Microclover Questions Answered (Part 1)
I recently
received an email from a user of microclover in Spokane, Washington. He
asked several good questions about microclover in his lawn, and I will try to
address these one-by-one in the next three or four blog posts.
Last year, I
was looking for a low maintenance lawn alternative and seeded microclover
directly into a neglected lawn (mostly weeds) this past spring. The
clover has grown in quite nicely, and although other weeds still are prevalent,
I have been mostly pleased with these rich green, no-watering, shade tolerant,
nitrogen-fixing plants. I have a few follow-up questions I thought you may be
qualified to answer, given your research into this new variety of clover.
Question 1. Since microclover does not flower, I am concerned
about it maintaining a long-term presence in my lawn. Will
the current plants die after a couple years, or once established, will it
remain perpetually, all other things constant? If the former, do
you have any ideas for how to maintain a long-term clover presence?
The first thing I should mention is microclover DOES produce
flowers. You may not have seen them yet because of where you are
located, the time of year, weather conditions, or perhaps the fertility level
of your soil. However, I have observed flowering in my plots in Pennsylvania
beginning in late May and lasting through June and into July. The
attached photo shows fewer flowers in plots amended with compost than in
non-amended plots. This is likely due to more soil nitrogen in the
compost plots (microclover appears to produce fewer flowers when an abundance
of nitrogen is present). One other interesting observation: I saw much more
flowering last year compared to the year. I’m not sure why, but it
could be due to differing weather conditions between 2013 and 2014, or the age
of the stand.
If your
microclover is not producing flowers, don’t be concerned about
persistence. Microclover lives year to year as a perennial, and can
spread around your lawn via above-ground runners (stolons). It
survives heat and drought, as well as tough winters. I was concerned
this spring when I saw some dead patches of microclover in my plots (killed by
the extremely cold and icy conditions during the winter of 2014). However,
most of the clover survived and gradually filled in the dead patches. Of course
nothing lives forever, and it’s possible the clover will eventually fade from
your lawn. Extreme drought, excessive traffic, too much nitrogen, and broadleaf
herbicide applications are factors that can negatively influence persistence of
your microclover. The longevity of microclover in lawns is something
I hope to examine over the next several years.
Friday, April 25, 2014
The Application of a Mathematical Model to Extrapolate Study Results to Other Locations
Environmental models are used to simulate or reproduce real world conditions and how those conditions change due to varying input. Modeling enhances our ability to extrapolate results from intensively-studied test sites to other potential use sites. These models are used by industry and governmental organizations alike to support scientific analyses.
Input will vary based on the model being used and conditions
the modeler would like to simulate, but it can include changes in land use,
land management techniques, weather data, etc. The model ArcSWAT 2009 is being
used to simulate conditions at the Maryland sites and to show how the incorporation
of BMPs (i.e., adding compost to the soil and using a lawn seed mixture
containing microclover) affects runoff.
Specifically, ArcSWAT is currently being used to model
runoff characteristics from the Clarksville, Maryland test and control sites.
ArcSWAT is an interface between Esri’s ArcGIS Geographic Information System and the SWAT model
(Soil and Water Assessment Tool) developed by Dr. Jeff Arnold of the USDA
Agricultural Research Service. SWAT is a physically-based model, which means it
relies on soil, elevation, land use, and weather data to simulate water and
sediment movement as well as nutrient cycling within a watershed. Therefore, it
allows one to examine how various management methods affect runoff. Subbasins
of the watershed are divided into hydrologic response units (HRUs), which are
areas of similar elevation, land use, and soil data. Ultimately, the model
simulates loadings from each HRU to the stream on a daily, monthly, or annual
time step.
The Clarksville test and control sites’ watersheds have been
delineated using ArcSWAT. We are currently working on
refining input variables in order to accurately simulate water, sediment, and
nutrient movement at each site. Once the input is complete we will be able to
run the model and compare the modeled results with the results of the on-going
monitoring. Ultimately, when the model is appropriately calibrated, the results
will be extrapolated to other sites throughout the Chesapeake Bay
watershed.
Thursday, April 3, 2014
Herbicide safety on microclover: Results from University Park
by Peter
Landschoot, Dept. of Plant Science, Penn State
As the use of microclover in lawns gains
interest among homeowners, questions will surface on how this species responds
to routine lawn care practices such as mowing, fertilization, and weed control.
Weed control practices are of particular concern due to the widespread use of herbicides
that may injure microclover. A recent study by McCurdy et al. (2012) at Auburn
University revealed that several common herbicides used in lawns effectively
control clover species, including atrazine, dicamba, clopyralid, 2,4-D,
triclopyr, metsulfuron, and trifloxysulfuron. However, these authors found that
2,4-DB, imazethapyr, and bentazon did not cause significant injury to clover,
and suggested they may be suitable for weed control in scenarios where clover
is a desirable species. Information is needed on the tolerance of microclover cultivars
to broadleaf and annual grass herbicides used to control lawn weeds in the
Chesapeake Bay watershed.
Treatments included three postemergence broadleaf herbicides
[Weedar 2,4-D Amine (3.8L); Aceto 2,4-DB Amine
(2.0L); and Rhomene MCPA (3.7L)] applied at two or three
different rates on September 6, 2012 and September 8, 2013 (Table 1). Also, five preemergence herbicides [Gallery 75DF (isoxaben) applied at three different
rates; Pendulum 60WDG (pendimethalin); Barricade 65WG (prodiamine); Dimension
1.0EC (dithiopyr); and Balan 2.5G (benefin)]; and one postemergence nutsedge
herbicide [Basagran T/O 4.0L (bentazon)] were applied on May 7, 2013 (Table 2).
All treatments were applied using a backpack sprayer at 40
psi with a dilution rate equivalent to 1 gallon water/1000 ft2. The experimental
design was a randomized complete block design, and each treatment was
replicated three times. Plot size was 30 ft2.
Criteria for evaluating herbicide tolerance included visual
ratings of foliar injury using a scale of 0-10, with 0 indicating no injury,
and 10 representing complete desiccation of clover. After the final injury rating was taken
during the 2012 and 2013 experiments, visual assessments of percent clover
cover were made.
Results
Late summer applications of 2,4-D amine at 2 and
3 pt/A caused noticeable injury and reduced cover of microclover when compared
to the untreated control in 2012 and 2013. Injury from the 3 pt/A treatment was
more severe than the 2 pt/A treatment in both years, resulting in an approximate
50% reduction in microclover ground cover in 2012 and 20% reduction in 2013. The
2 pt/A treatment resulted in about 20% less microclover relative to the control
in 2012, and a 15% reduction in 2013, 3-4 weeks after treatment. The 2,4-DB treatments
(2 pt/A, 4 pt/A, and 6 pt/A) did not produce visible foliar injury in 2012 or
2013, but the 6 pt/A treatment resulted in a slight reduction (8%) of microclover
cover in 2012 compared to the control 1 month after treatment. No reduction in
cover was observed with any 2,4-DB treatment in 2013.
No significant visible injury to microclover
foliage was observed with the 0.5 and 1.0 pt/A rates of MCPA in 2012. However, a slight reduction (8%) in microclover
cover was detected with the 0.5 pt/A treatment in 2012. In 2013 the 1.0 pt/A treatment showed some
minor foliar discoloration following the late summer application. Neither of the MCPA treatments resulted in microclover
cover reductions in 2013.
Although some significant reductions of microclover
were observed with 2,4-D applications in both years, the clover fully recovered
during the spring of the following year.
Table 1. Influence of herbicide treatments on Pirouette microclover following applications on September 6, 2012 and September
8, 2013 at the J. Valentine Turfgrass Research Center
in University Park, PA.
Clover
|
% Clover
|
Clover
|
% Clover
|
||||||
Product
|
Injury§
|
Cover
|
Injury
|
Cover
|
|||||
Treatments
|
Rate
|
9/21/2012
|
10/7/2012
|
9/16/2013
|
9/30/2013
|
||||
2,4-D Amine (3.8L)
|
2 pt/A
|
3.7 b¥
|
72 c
|
4.0 b
|
81 b
|
||||
2,4-D Amine (3.8L)
|
3 pt/A
|
6.7 a
|
45 d
|
6.3 a
|
75 b
|
||||
2,4-DB Amine (2.0L)
|
2 pt/A
|
0 c
|
92 ab
|
0 d
|
97 a
|
||||
2,4-DB Amine (2.0L)
|
4 pt/A
|
0 c
|
85 ab
|
0 d
|
97 a
|
||||
2,4-DB Amine (2.0L)
|
6 pt/A
|
0.3 c
|
83 b
|
0 d
|
95 a
|
||||
MCPA (3.7L)
|
0.5 pt/A
|
0.7 c
|
83 b
|
0 d
|
97 a
|
||||
MCPA (3.7L)
|
1 pt/A
|
0.7 c
|
87 ab
|
1.0 c
|
95 a
|
||||
Control
|
0 c
|
91 a
|
0 d
|
98 a
|
|||||
§Foliar injury visually assessed using a scale of
0-10, with 0 indicating no injury, and 10 representing complete desiccation of
clover.
¥Data means within the same column
and followed by the same letter are not significantly different as determined
by Fisher’s Protected Least Significant Difference test at P=0.05.
None of the preemergence annual grass herbicides used in the
spring 2013 trial (Pendulum
60WDG, Barricade 65WG, Dimension 1.0EC, and Balan2.5 G) resulted in any visible
injury or thinning of microclover. However, all three rates of Gallery 75DF
showed considerable injury, leading to thinning of the stand. The only postemergence nutsedge herbicide
used in the 2013 spring trial (Basagran T/O) did not produce visible injury
symptoms or thinning.
Based on results of the spring 2013 trial, Gallery 75DF
should not be used in stands of microclover.
This trial will be repeated in 2014.
Table 2. Influence of preemergence herbicide
treatments and one postemergence herbicide (Basagran) on Pirouette microclover following applications on May 7, 2013 at the J. Valentine Turfgrass Research Center in
University Park, PA.
Product
|
Injury§
|
Injury
|
||||
Treatments
|
Rate
|
5/14/2013
|
17-May-13
|
|||
Gallery 75DF
|
0.66 lb/A
|
2.0 ab¥
|
5.3 ab
|
|||
Gallery 75DF
|
1.00 lb/A
|
2.3 ab
|
4.3 ab
|
|||
Gallery 75DF
|
1.33 lb/A
|
3.7 a
|
5.3 a
|
|||
Basagran T/O (4.0L)
|
2 pt/A
|
0 c
|
0 c
|
|||
Pendulum 60WDG
|
3.4 lb/A
|
0 c
|
0 c
|
|||
Barricade 65WG
|
1 lb/A
|
0 c
|
0 c
|
|||
Dimension 1.0EC
|
2 qt/A
|
0 c
|
0 c
|
|||
Balan 2.5G
|
60 lb/A
|
0 c
|
0 c
|
|||
Control
|
0 c
|
0 c
|
||||
§Foliar injury visually assessed using a scale of
0-10, with 0 indicating no injury, and 10 representing complete desiccation of
clover.
¥Data means within the same column
and followed by the same letter are not significantly different as determined
by Fisher’s Protected Least Significant Difference test at P=0.05.
References:
McCurdy, J.D., J.S. McElroy , and M.L.
Flessner. 2013. Differential response
of four Trifolium species to common broadleaf herbicides: Implications for mixed grass-legume swards.
Weed Technology, 27(1):123-128.
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