That is the question. With the celebration of the 400th anniversary of William Shakespeare’s death on the weekend, I couldn’t resist this title. My apologies Will!
This blog is a follow up to a Twitter conversation on tissue testing between @paceturf, @djsoldat and @asianturfgrass a couple of weeks ago. By the way, Twitter with its 140 character limit is not a very good forum for this type of discussion so hence an attempt to visit this topic in this blog.
Is there a role for tissue testing in turf management?
In my years working at OMAFRA we saw the role of tissue testing as a supplement to soil testing if there was an existing problem that could not be explained by the soil test results. It was not something that was recommended on a routine basis. Often when a nutrient is present in adequate amounts in a soil test but not in a tissue test the reason is because of a problem in the rootzone such as compaction, waterlogging or black layer.
Dr. Larry Stowell and Dr. Wendy Gelernter of Pace Turf have an excellent article that deals with the pros and cons of tissue testing. The full article can be found at https://www.paceturf.org/PTRI/Documents/Soil_tis/0201.pdf I have attempted capture some of the information below.
The importance of sample collection and preparation
The quality of the tissue sample that is sent to a laboratory for analysis has a huge impact on the quality of the laboratory results. Very specific guidelines are given by Pace Turf and are summarized here.
- Clean out mower baskets thoroughly before collecting samples. This includes old clippings, dust, topdressing material, fertilizer, etc.
- Do not collect clippings immediately after a fertilizer, pesticide or topdressing application.
- Select greens or a green that is performing well and select the problem green or greens.
- Mow enough turf to fill the basket 1/3rd
- Collect roughly 1 litre of clippings and label each sample carefully with a waterproof marker.
- Thoroughly wash each clipping sample in a clean bucket. Turf tissue will float and contaminants (fertilizer and topdressing will sink).
- Spread a layer of washed clippings (2.5 cm deep) on labelled newspaper in a clean dry place and all them to dry. Overnight will suffice.
- Place dried clippings in a new, clean, dry, labelled paper bag. Close bag and secure with a rubber band.
Figures 1 shows a turf tissue sample that was received at Brookside Laboratories. In this case 95% of the sample was contaminants (topdressing) and 5% of the sample was the turf tissue. Figure 2 shows a turf tissue sample that was not properly dried before being sent to the lab. It looks bad, the smell was even worse. Neither of these samples would provide meaningful results had the tissue test been run.
Are tissue test results reliable?
Nutrient levels in the turfgrass plant vary so much. They will vary from day to day and week to week. Some of the reasons for the variable are a result of:
- the amount of turf growth
- air temperature
- amount of light
- soil moisture
What is driving the renewed interest in tissue testing?
There has been a body of really good research that is giving information on the role of potassium (K) in anthracnose susceptibility in annual bluegrass, snow mould susceptibility in creeping bentgrass and winter survival of annual bluegrass. This information is giving superintendents precise K tissue percentages to aim for better resistance to certain diseases and winter survival.
K and snow mould
Let’s talk about the role of K in snow mould susceptibility in creeping bentgrass. Dr. Doug Soldat’s research has shown that creeping bentgrass going into winter with 1.8% tissue K will have less or virtually no snow mould than creeping bentgrass will higher K tissue levels based on his trials in Wisconsin. This is fantastic information and if you have seen Dr. Soldat’s photos on Twitter showing this, it is really impressive. He is recommending tissue testing for K three times a year – spring, summer and fall.
My question to you as golf course superintendents in Canada is “If you have tissue K at 1.8% in your creeping bentgrass going into the winter are you going to forego your preventative snow mould applications?” I think knowing the tissue K level is good information, but is it going to change your fungicide program going into the winter? Probably not.
K and anthracnose basal rot
Chas Schmidt’s research at Rutgers has shown that annual bluegrass will have more anthracnose if the tissue K levels fall below 2%. Again, this is really interesting information. I can see wanting to know this information to be used as part of your anthracnose management program. I emphasize “part” of your anthracnose management program. Other factors that are important in an anthracnose management program for annual bluegrass are N fertility, mowing height, topdressing frequency and lastly a fungicide program.
So, if you are a golf superintendent managing annual bluegrass putting greens with a chronic problem with anthracnose basal rot that you are not able to get under control it using the other management practices, it might be good to do a tissue test for K to see if they are below the 2% that is recommended.
K and winter injury
The work at Rutgers by Chas Schmidt also indicates that if tissue K levels in annual bluegrass fall below 2% there is more chance of winter injury. Work by Katie Dodson at Olds College shows similar results. She found that annual bluegrass had the lowest LT50 when tissue K was between 2.5 and 3.5%. If you are a golf superintendent with Poa annua greens in an area which experiences winter injury, making sure that your K tissue levels are > 2% going into the winter is probably a good idea and may be a good reason to tissue test. Don’t forget the role of N in winter survival as well. Dodson’s work showed an 1:1 ratio of N:K in the annual bluegrass tissue was best.
Tissue testing for N fertilization
There are many factors that influence how much N a turfgrass plant needs at any one time. Some of the factors are turf species, temperature, soil type, etc. Dr. Micah Woods of the Asian Turfgrass Centre and Drs. Stowell and Gelernter from Pace Turf have been working on a growth potential model that involves many factors but focuses on temperature and light. N rates can be adjusted monthly based on these two factors to maintain optimum turf growth. This method of determining N requirements for turf does not rely on tissue testing. More information on this model for N rates and timing can be found at http://www.files.asianturfgrass.com/201306_growth_potential.pdf
So this all brings me back to my first question – is there a role for tissue testing in a turf fertility program? If superintendents are fertilizing according to the MLSN guidelines for nutrients, turf should be performing well. If you are managing annual bluegrass and are concerned about K levels on your greens for maximizing winter survival, you may want to experiment with tissue testing or if you have a chronic problem with anthracnose basal rot. If you are managing predominantly creeping bentgrass greens, tissue testing for K will provide you with information on whether you are in the zone (1.8% K) for minimizing snow mould, but it probably won’t impact your decision on preventative fungicide application for snow mould control.
Soil testing is still the backbone of a turf fertility program for nutrients outside of N. The growth potential model is a tool that can be used to schedule N that does not rely on tissue testing. There may be some good reasons for you as a superintendent to perform tissue tests if problems exist or if you are trying to dial in your K levels for winter-hardiness, but it probably isn’t necessary to perform biweekly or monthly tissue test to have good quality turf on your greens.
We at DCS & Associates welcome your feedback and comments on the issue of tissue testing. We would like to hear your thoughts, if you agree or disagree with with them. Differences of opinion always lead to an increased understanding of the issue. You can add a comment on the blog or email us at firstname.lastname@example.org, email@example.com or firstname.lastname@example.org or comment on Twitter.