Observations from Wisconsin and How Dr. Soldat Would Manage Potassium on Cool-Season Turf

Hello again from the Midwest. Its be a while since I have posted and its because old man winter will not relinquish his grip on us. We have only had the opportunity to rate one of our 5 snow mold sites. Last week three of our sites received another 5 to 12 inches of snow. Where the snow has melted, I am assuming winter kill and breakthrough were minimal. My only metric to assess this is my phone has been eerily quiet. So since I do not have much to report on with respect diseases, I am privileged to post comments from Dr. Doug Soldat on managing potassium on cool-season turf. I think this fits well into the discuss John started concerning Poa management.

Turf Diseases Blog: How I’d Manage Potassium on Cool-Season Turf

Doug Soldat

Dept. of Soil Science

University of Wisconsin-Madison

Over the last several years as the turfgrass nutrient and water specialist at the University of Wisconsin-Madison, I’ve slowly been developing my philosophy of potassium management based on my research, the scientific literature, theory and observation. I teach my view point every fall to a group of students who are too green to be shocked, but when I revealed my philosophy to a group of workshop attendees at the Canadian International Turfgrass Conference in Vancouver in March, it was clear that my recommendations were a major reversal from what they’ve been taught. Similarly, you may have heard Dr. Rossi (Cornell) and Dr. Gaussoin (Nebraska) debate the importance of potassium at GIS and elsewhere. So, I thought I’d throw my hat into the ring; and because disease plays a major role in my management philosophy, I’d thought I share my thoughts with this community. A much more detailed defense of the ideas below will be published in the Grass Roots in June (official publication of the Wisconsin GCSA). I’d be happy to email you a copy of that when it’s available, just let me know djsoldat@wisc.edu. So, without further ado, here’s how I’d manage potassium if I were a Golf Course Superintendent:

Fairways:
I’d apply potassium only according to soil test levels. I’d use modern interpretations of optimum (i.e. 50-100 ppm, depending on soil test) instead of the more common values of 200-400 ppm. I expect even the 50-100 ppm levels will be adjusted downward as more soil test calibration studies are conducted, but for now 50-100 is fine.

If/when potassium dips below that soil test threshold, I’d make a 1 lb/M application in May. I’d re-test the soil in fall to determine if another application is warranted the following spring. Why May? The evidence for potassium improving drought tolerance is much more convincing that the evidence that potassium increases winter hardiness (although, I believe the opposite is true for warm season grasses). Also, Dave Moody and Frank Rossi’s work at Cornell University has clearly linked increased potassium in the leaf to increased severity of gray snow mold (and pink to a lesser extent). Similarly, Dr. Ebdon et al. (2006 – Mass.) reported more severe gray snow mold at higher K application rates on ryegrass. In summary: there is only weak evidence that K increases cold tolerance for cool season-grasses, strong evidence that it increases snow mold, decent evidence that it improves drought tolerance. I’d go with May.

If my fairways were something other than sand, I’d apply muriate of potash (0-0-60), if they were sandy, I’d consider using a polymer coated K source or spoon feeding in 0.25 lb/M increments if practical. Most non-sand soils have a high enough cation exchange capacity to retain a 1 lb/M application of potassium. Sandy soils may need some help provided by the polymer coating or spoon feeding approach.

Greens:
Assuming most greens are sand-based, either from construction or years of topdressing, I’d spoon feed potassium along with nitrogen in the ratio of 2 parts nitrogen to 1 part potassium beginning in May and ending in August (but continuing with N after that). I like to fertilize my research greens about every other week with 0.2 lbs N/M as urea, so that’d put me at 0.1 lbs K₂O/M per application or about 1.0 lbs/M for the season. I feel this is a very conservative approach which replaces the potassium removed by clippings. But as the research continues to unfold, I can imagine that my management philosophy for greens may evolve to look more like my fairway program. That said, if I were an actual superintendent, I’d leave the research to the researchers and use this conservative but research-based approach.

Why stop in August? Same philosophy as above, the benefits of potassium as a drought stress nutrient are much more convincing that the cold tolerance argument and we have seen that high tissue K increases snow mold pressure. Also, research by Woods et al. (2006 – New York) and Johnson et al. (2003 - Utah) has shown clearly that high soil potassium levels in sand based greens are always substantially reduced by spring, presumably by the snow melt leaching the potassium out of the root zone. Therefore, a large application to a sand root zone in fall will do two things: increase your susceptibility to gray snow mold, and 2) leach out of the root zone, becoming unavailable in spring resulting in a complete waste of time and resources.

One Final Note:
All this talk recently about fostering an environment that favors bent over Poa makes me wonder why a superintendent with such a mindset would want to apply any potassium at all. Poa is obviously more susceptible to heat, drought, and cold stress than bentgrass, so why apply a nutrient that supposedly increases tolerance to those things? Yet, I’ve not heard mention of potassium management as a key strategy. I’m not saying it should be -- I tend to think we’ve overestimated the role of potassium in stress tolerance —it’s just interesting that potassium has been left out of the discussion so far.

Poa annua management strategies (Part 2)

Last week I introduced the topic of annual bluegrass management practices that are gaining momentum in the United States and other parts of the world. While these practices have been met with some controversy, they have also made us as researchers spend a little more time investigating the implications of these practices for golf course superintendents.

One program that has emerged among many superintendents (many with a strong voice on twitter including @nccturf, @MinikahdaTurf, among others) is the incorporation of various management techniques that seek to favor the bentgrass over the weaker Poa annua spp. While there is much variation in the programs and none are identically alike, a general overview of some of the practices incorporated into the program were discussed in last week's post.

As I also mentioned in last week's post, those of you managing Poa (regardless of your management goals) usually have a very vocal and firm belief of why your program(s) works. As an academic, I try not to jump on anecdotal claims, but do like that they can serve as a catalyst that drives research. For me, it's about trying to figure what works and what doesn't (again based on research) and then trying to fine tune those results into programs that are repeatable across a variety of regions and under different management and environmental situations. So, in 2010 we initiated several studies looking at the management and suppression of Poa under golf course putting green conditions.

Kyung Han assessing Poa populations

Four studies were initiated investigating the interactions between and among the following variables: 1) low and normal/high seasonal nitrogen rates (low and high are about 0.5 and 2.2-3.0 lbs N/1000 sq ft/year); 2) plant growth regulators (none, Primo, and Cutless); and 3) Ferrous sulfate rates (0.0, 0.25, and 1.0 lb/1000 sq ft every 3 weeks).  There are a lot more details to the trials, but since this is only the first year and we have another full year of the study (and hopefully several years more, funding pending) I will save the details for the publication. Other common factors in the study include: routine topdressing, no disturbance, routine venting with solid tines, minimum irrigation where possible, no phosphorous applications, pesticides only where needed, and probably others that I am forgetting. The studies were setup as a 2x3 or 2x3x3 factorial with four replications.

Trials were initiated on a research putting green at the Joseph Valentine Turfgrass Research Center to investigate the interaction of N rates, PGRs, and Fe rates on annual bluegrass populations on a putting green.

So as not to bore everyone with a ton of data, I have included one slide showing results of the 3-way factorial study which included all factors. Data shown is only a single date and it should be pointed out that tremendous seasonal variation in Poa annua was observed between summer and fall timings. Total Poa was estimated at 20 to 25% throughout the area at the beginning of the study and here are the results after the first 5-6 months of initiating the first treatments.

Poa annua populations following the seasonal application of various N rates, Fe rates, and PGRs. Data were collected monthly, but peak annual bluegrass ratings taken in October 2010 are shown here.

Now there is a lot of data to be analyzed and interpretation will definitely be reserved for AFTER we have two full years of data, but here are the general summaries that I have based on this first year:

1. Nitrogen rate (0.5 vs. 2.2 lbs N/year) appeared to have an slight impact on Poa annua populations with lower N resulting in lower % Poa in October.
2. PGRs had the greatest impact with Cutless treated plots (as expected) reducing Poa the greatest. Interestingly, the Primo-treated plots appeared to reduce populations when comparing low to high N plots, but these data need to be subjected to contrasts which have not yet been done to determine the significance of this effect.
3. Ferrous sulfate so far does not appear to have any impact on the Poa annua populations. Many utilizing this program are suggesting that these applications are important to reducing Poa, but based on this first year data it does not seem to have much impact. Having said this, the turf color/quality in plots receiving low N levels started to decline and in plots where Fe was applied it did appear to help improve the overall color...although quality was still a little suspect.

So, this is the first look into the data that we have from the first year of our Poa management study. There are probably a lot of questions about some of the details of the study, but I am leaving that for another time as I hope to continue this work for several years.

The main questions that I have regarding the long term impact of this study will be the assessment of organic matter buildup, changes to the pH (of which we have seen none yet), and the development of side problems such as black layer due to the sulfates. I have also been told that this program will result in a substantial reduction in disease severity and therefore a reduction in the overall use of pesticides. These will all be things that we look at as the study progresses this year and beyond. In addition to these studies, we will be looking at more chemical-based means of suppressing the weed as well...we can't rely on just one method and most likely it will take a combination of chemicals (or "poisons" as our friend "Poa annua" on facebook calls them) and sound management practices to get Poa populations where you want them.

Acknowledgements

As many of you know, funding for these research projects can be expensive. This research could not be possible without the support of The Penn State College of Agriculture and Department of Crop and Soil Sciences, The Center for Turfgrass Science, The Pennsylvania Turfgrass Council, SePro, and the USGA.

Green-up, and horse poo

*Green up*

The cool season grasses are greening up nicely here in Manhattan. So far I haven't seen many signs of greening up in the warm-season grasses here, but a few days ago a superintendent from South Central Kansas shared photos of bermudagrass showing a lot of green, more than he's ever seen for this time of year. Another from Central Kansas reported a little greenup in his area too, early for his site. How is the green-up of C4 grasses in YOUR area? Early? Are you ready???

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*Horse poop in the lawn*

This was my favorite turf question over the past few days. By a round-about way, I learned that it was even worthy of a few Tweets :)

Here it is for all to enjoy:

http://www.ksuturf.org/blog/2011/03/question-of-the-week/
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*Dicots are people too*

I know, it's a turf blog, but I can't help throwing in a few trees and ornamentals every now and then.

If you manage pine trees on your course, you might be interested in some info about pine tip blight. It's a very common disease in this region, and it occurs in the upper midwest and northeast, too.

I posted some stuff on a K-State website and you can check it out HERE

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Lot's of talk about Poa this spring

Winter damage can be a big problem in Poa.

While some golf course superintendents are still seeing the last remaining traces of snow on their turf, most are starting to assess the impact of winter and potential damage. With the predominance of Poa annua as the primary species on many golf courses throughout the region, the potential for winter damage is always high and it appears that the winter of 2010/2011 may be as damaging as that in the summer of "the year that shall not be spoken". According to a recent Northeast Regional update from the USGA's Adam Moeller, it appears that many golf courses have "discovered moderate to severe winter damage on putting greens."

So much of the discussion on Facebook and Twitter has shifted to assessing the damage and fixing it.  In cases where damage was not observed the focus has been on seedhead suppression. The bottom line for those managing turf in the Northeast, the focus surrounds the suppression and/or management of Poa annua.

Regardless of whether you want to manage or suppress Poa, you probably feel pretty strongly about your beliefs!

While this has always been a major interest of mine, the shift to Penn State has given me the opportunity to focus more research efforts on managing this species on golf courses. For those not familiar with our state, Pennsylvania is made up of two major factions: those in the western portion of the state (e.g., Pittsburgh) love their Poa and believe it is the premier species for putting quality while those on the eastern side of the state (e.g., Philadelphia) generally consider this a weed problem and go to great lengths to suppress it (there are always exceptions to the rule, so don't you superintendents in Pittsburgh trying to control Poa yell at me telling me that I am wrong). That leaves me and others at the University trying to figure the best management practices for both those that want to get rid of it and those that want to promote it. And while there are many people that claim to know how to accomplish this, a lot of research-based information is still needed to determine best management practices that meet your specific needs (whatever your needs may be).

So over the next two weeks, I will try to provide some insight into what is generally known about managing/suppressing Poa in our region and provide some insight into research that we have initiated to further assess management options.

Here is a list of what is generally known or believed about Poa management:

Trimmit-treated stand of bent/Poa

PGRs
Primo and Trimmit/Cutless are the three most common growth regulators applied to turf during the season. Primo is believed to have little impact on Poa (other than making it stronger), while Trimmit and Cutless have been show to favor the growth of bentgrass over annual bluegrass when used a repeated application program.

Herbicides
There has been no silver bullet herbicide for managing annual bluegrass. Preemergent herbicides effective against Poa are generally not recommended for use on putting green turf. Postemergent herbicides such as Prograss and Velocity have been used with varying results, but again are not labeled for use on putting greens. Various experimental products (cumyluron, methiozolin, others) are currently being evaluated in the United States and have shown great promise. For example, methiozolin is currently labeled for putting green turf in Korea and has excellent efficacy in preliminary studies, but more studies looking at the use of this product are needed.

Coring can create an ideal Poa seedbed

Cultural practices
This is where we get into the relatively ongoing controversy of management programs. In recent years, there has been a resurgence of programs that involve minimal disturbance (no hollow tine aerification or deep vertical mowing), low nitrogen and phosphorous programs, high ferrous sulfate (and other sulfates) applications, and others. Unfortunately, many of these recommendations are based on "theory" and have not be thoroughly evaluated in controlled research environments.

The general feeling regarding cultural practices for suppressing Poa as I understand it are:

1. Low nitrogen will favor the bentgrass over the annual bluegrass and in turn result in less accumulation of organic matter. ADDED CONTENT: (Low P will also favor bent...thanks Dr. Koski for pointing this out)
2. Ammonium sulfate as a primary N source will result in acidification and therefore further favor bentgrass.
3. Fe, Mg, and Mn sulfate will help in an acidification of the foliage (not sure where this came from) and therefore favor bentgrass AND help to offset color deficiencies in low N programs.
4. Core aerification surrounding times when annual bluegrass germination is optimal should in general be avoided. Many of these new Poa management programs dictate that greens be vented often, but that any disruption should be avoided.
5. To further help dilute the potential build-up of organic matter, frequent topdressing is generally recommended to encourage the development of a manageable "mat" layer rather than a puffy "thatch" layer.
6. I have no idea where this fits into the program, but many seeking to reduce Poa populations are lowering their mowing heights. This seems counter intuitive to me, but that's what I'm seeing and hearing.
7. As would be expected, irrigation is minimized to further stress the Poa and favor bent. In this entire program, this one seems like a no-brainer to me and the diligent and thrifty use of water is in general a good idea for limiting Poa as well as associated turf diseases.
8. There are probably other things that I have left out, but this post is already getting too long...add your "#8" in the comments or on Facebook.

So now you have a general overview of some of the techniques that superintendents and greenkeepers are using around the United States and around the world. Please feel free to add to the comments any additional positive or negatives you see with these management practices. Some of them are controversial to say the least and I have seen people swear by all or a selection of these practices to help "favor the strong species while eliminating the weak" and I have seen others who after several years on the program(s) lose a significant amount of turf.

Next week, I will share some preliminary results of our modified version of the program above which investigates the interaction of nitrogen rates, ferrous sulfate rates, and plant growth regulators on Poa annua populations.

Aer-i-fy, good tines, come on!

Apologies to Kool and the Gang. Really, my whole posting this week is centered around the fact that that horrible pun came into my head. When you get a song stuck in your head, you have to listen to the song a few times and it gets cured, right? Maybe writing about Aer-i-fy will cure me of singing it in my own head.

So, the reason I was THINKING about aerification today was because I was thinking back to 2010. By the way, maybe we should not even SAY "2010". It will be like calling John's friend Voldemort (see below) "you know who" or "he who shall not be named." 2010 will be "you know when" and "the year that shall not be spoken."

ANYWAY:

Many of last year’s turf health problems were related to root health, thatch, organic matter, etc etc. Sometimes those issues caused problems-o'-plenty on their own. Sometimes they made the turf more susceptible to diseases.

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The USGA (US Golf Association) just posted a bunch of information about aerification.

Video: Why aerating a course is vital. Click HERE

Video: Why aerate greens. Click HERE

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Check out this photo: The turf in the aerification holes is more robust. I wish I had photos of turf plugs/cores. I’m confident that the roots in the aerification holes were much more developed and deeper.

A more extreme site:

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Speaking of GREEN:

(Are you still with me? Bonus points for you… Yes, I keep track of points for all of you loyal readers.)

As a descendent of Irish immigrants (my great-great-great-great grandparents) I try to celebrate St. Patrick’s Day each year. Yesterday some friends and I played Irish tunes outside the KSU student union. I’m the one on fiddle. We even got some students dancing for awhile! I hope you all had a lovely day. We are all a little Irish on March 17

Fungicide Programs: Take this short survey and win!

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Thank you in advance for your assistance on this project!

Healthy Grass = Little Disease

I've seen a lot of healthy grass in Asia over the past couple of months. This tends to be the driest season of the year for much of Southeast Asia, and no matter what type of grass is being grown, I haven't seen much disease. A bit of curvularia on Zoysia matrella in Thailand, some fairy ring on Tifeagle bermudagrass that was a trifle peckish, and the ubiquitous dollar spot, especially on seashore paspalum.

For management of dollar spot on seashore paspalum, assuming it is still warm enough for the grass to grow, I recommend keeping the leaves drier, the soil wetter, and applying a bit more nitrogen. We've looked at various treatments of calcium, potassium, nitrate vs. urea as a nitrogen source, etc., and we have detected no effect on dollar spot intensity of seashore paspalum. Creating a more salubrious environment for the grass invariably solves the problem.

Speaking of salubrious environments, I don't think there is a better place for a turfgrass conference than Thailand. Working on behalf of the Thailand Golf Association, the Thai GCSA do a great job putting together all the logistical details of the Sustainable Turfgrass Management in Asia conference and we get tremendous support from The R&A and from the golf course superintendents who travel from all parts of Asia to attend this educational event.

How's the Spring Dead Spot?

This is probably the most common question I get this time of year as everyone anxiously waits to see how much disease there will be this year or if their preventive fungicide applications worked. Based on our winter weather conditions, with cold temperatures combined with periods of wet and dry weather, I expect the disease to be pretty severe this year and early reports seem to indicate that it's going to be a bad year. We've even had a report of a severe outbreak of the disease on zoysiagrass fairways.

Unfortunately, my travel is limited this time of year due to classes and conferences, so let me ask you: How's the spring dead spot out there? Any particular successes or failures with fungicides? Please post a comment to let us know what you're seeing!

Superintendents Encouraged to take Anthracnose Survey!

TAKE THE SURVEY

As you may remember a relatively large group of researchers from various universities across the country have been actively working on research related to the management of anthracnose basal rot of annual bluegrass. The project started about 5 years ago and was kicked off by gathering information from about 400 superintendents and turf professionals to figure out what was happening in the field and what was lacking the way of research-based recommendations. Well we have come to the end of the first phase of the project and are hoping to 1) gather information about your current management strategies and 2) utilize this information to fine tune our research priorities over the next 5-year phase of the project.

Thanks to the help of the Golf Course Superintendent's Association, we have launched our follow up survey that many of you requested to be a part of. Well now's your chance. Please help us in our goal of finding better solutions to your anthracnose problems by filling out the online survey.

TAKE THE SURVEY