Monday, 10 September 2012

Western Canada Growth Potential Comparison

My last post showed how the growth potential for cool season turfgrass in Western Canada was not at all like that that is commonly used. The common growth potential with peaks in spring and fall is more typical of areas like California. I have compiled the data for a number of areas in Western Canada to show what the growth potential for bentgrass looks like.

It turns out that the only place in BC or Alberta that really exhibits a slowdown in growth potential in the summer is Osoyoos. Naturally Osoyoos is the warmest and driest city in Canada.

I have always joked that Vancouver is "God's Country" and this graph just goes to prove that. Look at how long our maximum growth potential lasts. This part of the world is the perfect spot for growing cool season turf grasses.

Looking at the Banff growth potential you can see just how short of a growing season they really have. Edmonton and Calgary have longer growing seasons that Banff but they struggle to reach even 75% of the growth potential.

I have also graphed the recommended nitrogen application rates and timings for these cities based on the growth potential model.
Nitrogen rates based on a maximum nitrogen use rate of 3.5g N m2 for bentgrass.
This is pretty cool stuff. Theoretically turf managers in Edmonton could use half as much nitrogen than those in Vancouver. Even though Osoyoos has a much colder winter than Vancouver it still requires a greater nitrogen rate based on it's very warm and extended summer. A short distance north from Osoyoos in Kelowna and the nitrogen requirements are less than that of Vancouver. Interesting stuff.

Take a look at this data and compare it to what you are currently doing. I really look forward to any feedback from turf managers from Western Canada.

Sunday, 9 September 2012

How Much Nitrogen?

How do you decide how much nitrogen to apply and when? I have always used research showing the relationship between disease pressure and nitrogen rates as the basis for my fertility program. In general, nitrogen rates higher than 2kg/100m2 per growing season resulted in more fusarium. Fusarium is my number one pest so obviously I plan most of my agronomic practices around prevention of this fungal disease. Once I had the total rates I would basically just divide the total by the number of growing months I had in my climate or 8 giving me a number of around 0.25kgN/100m2 per month. I would then tweak these amounts based on the following growth model for cool season turf.
For the most part this growth model is exactly how cool season turf performs in most cool season climates. The only problem is that being on the West Coast of Canada I maintain turf in an extreme range of this climate. My climate is extremely not extreme or temperate. It really doesn't get that cold in the winters and in the summers our average temperatures rarely rise over 20C. The only problem for me is that that previous growth model is based on colder winters and warmer summers than I experience in my location.

The West Coast of Canada 
is an extremely not extreme climate!

It wasn't until recently that I came across this article by Micah Woods Ph.D. (Asian Turfgrass Center) which shows how the Growth Potential equation, developed by the fine folks at PACE Turf, can be used for calculating nitrogen requirements based on your specific climate. To me this was ground-breaking stuff. I always knew that nitrogen rates should be based on growth rates but it was too hard to for me to figure that out.

The resulting data from this growth potential model was amazing. It turns out that in my climate the typical cool season growth model was completely wrong. On the coast we never really got temperatures high enough where the growth rates of cool season turfgrass slowed. In fact we barely reach the maximum growth potential for most cool season turf species in our climate. In our warmest month (August) we only reached 94% of the growth potential. It turns out that in my climate the growth rates more closely resemble those of warm season turfgrass. Cool!

Cool Season Turf Growth Potential for my climate
Dr. Micah Woods has been doing some really interesting research lately regarding turf selection based on climate as well as turf nutrition. I highly recommend checking out his blog for the latest and greatest information in the fields of turf nutrition and selection. Personally I feel that this kind of work is really forward thinking and important for the turf industry. For too long we have been forcing turf to grow where it's not best suited. Furthermore we have been creating a whole string of problems by not fully understanding turfgrass nutrition and soil science. Again, check out what he is doing, it is focused on warm season turf but it all applies to cool season turf as well. I have a hunch that he is going to post a lot of really cool data in the next few years. I can only hope and pray that he eventually does some cool season climate comparison work similar to the stuff he has already done for warm season turf (nudge nudge, wink wink).

Recently I was contacted by Micah, knowing that I closely monitor growth rates and have recently switched to the growth potential nitrogen model, who requested some of the growth rate data that I had been collecting over the last year. He wanted to compare growth rates with average temperatures and nitrogen application rates. The resulting chart clearly shows that the growth rate of my putting greens is more closely related to temperature and less so on nitrogen rates. Growth rate is measured in Baskets/day on my greens mower.
Data Compiled and Charted by Micah Woods Ph.D.

You can clearly see that in the Spring of this year I was applying a higher amount of nitrogen to my putting greens than August but the growth rates were still less than they were in August. It wasn't until June that I switched my nitrogen rates to the growth potential model. Even though my nitrogen rates dropped slightly you can see that growth rates continued to climb along with the average temperatures. I can't wait until next year to see how the data compares and the turf performs. I have a hunch that all three lines will be similar but who knows.

Recently I've had problems with equipment breakdowns and haven't been able to adequately fertilize my putting greens as can be seen at the end of this chart. Data collected over the next year will more clearly show the slowed growth rates this fall.

We also discussed the different ways that turf managers have historically applied nitrogen. Until recently I had basically applied nitrogen at a constant rate throughout the season. This is typically how most turf managers apply nitrogen. Sure we tweak here and there but for the most part it's not that different. This method can produce great conditions but is it the best way? The whole environmental movement recently has really focused on reducing inputs and only applying to the course what is actually needed. This growth potential model is an excellent tool for figuring out how much N your turf needs and avoids wasted applications. Remember, the amount of nitrogen that the plant is able to use is dependant on the temperature, not necessarily how much you throw on. It should be really interesting to see how this theoretical nitrogen use will apply in the real world over the next few years. Maybe higher nitrogen rates on the potential could be beneficial especially during spring green-up. Again time will tell. Again it's almost fall and I can't wait until next spring!

The following chart shows growth rates on my putting greens over the past 3 weeks. The soluble nitrogen applications are pretty obvious. At first we see a spike in growth but the growth rates quickly return back to normal a few days post application which is to be expected with 100% soluble nitrogen. Of course the magnitude of this growth spike can be managed by applying slow release fertilizers or soluble fertilizer in light and frequent applications like I do. This growth spike is one of the main reasons I use a 100% slow release nitrogen fertilizer on my fairways. I don't have the luxury to apply fertilizer light and frequent on my fairways. This 100% slow release virtually eliminates the growth surge following application.

Soluble nitrogen is often used for quick growth surges to recover from damage or cultural practices like verticutting and aeration. The above chart really makes this point clear with the quick growth surge often only one day post application. What is important to note is that after the quick surge of growth the typical growth rates resume based on temperature. I would really like to see data from putting greens maintained with partial slow release N and 100% slow release N.

Brainstorm time!

The main benefit that I see from using the growth potential model is producing a healthier plant. Since switching over to this fertilizing method I have seen a huge improvement in my turf health which can't be seen on any of the previous charts. Typically during the summer months I would reduce my nitrogen inputs as this is what I was taught to do. The only problem for me was that in my climate this is the wrong thing to do. Dollar spot is a big issue on putting greens in the summer and it can be successfully controlled with timely nitrogen applications. I have to say that a big part of my dollar spot control success this summer was due to the increased nitrogen rates. I also hypothesize that the reduced nitrogen rates in the spring and fall could have an effect on fusarium incidence.

Another benefit of using the growth potential model as well as monitoring actual growth rates is the ability to monitor the turf's ability to handle stress. Managing turf stress is key to reducing pesticide inputs and in producing good healthy turf. I can now easily see when my turf is able and not able to handle stress and I can change my maintenance practices to better suit this. There is no point in me applying a ton of nitrogen to help the turf fight disease if the turf doesn't even have the ability to effectively use it. Going into this fall I now have a really good idea of when I can use certain aspects of my fusarium management plan and when I will have to rely on other aspects.

Even another potential benefit of using this model is thatch reduction. By minimizing nitrogen inputs and matching them to their use potential there could be a reduction or no net gain of thatch. I really look forward to any research that is done on this topic in the future.

It has been a very enlightening year so far in regards to putting green fertility. Basically everything I leaned in college 8 years ago has been thrown out the window. I am now using the MLSN guidelines and have based nitrogen inputs on the growth potential for my climate. I have to say, this new way of doing things is working a lot better than the old way. I have cut my fertilizer budget by 60% and have drastically increased the quality and health of my putting surfaces. Almost all guesswork has been eliminated and I can make fertility decisions with confidence.

A big thank you to Micah Woods for coming up with the idea on how to use the data I had collected. When I first stated collecting growth rate data I had no idea how interesting and useful the results would be! I really look forward to his research on the subject.

And you thought I was kidding when I said I'd let the rough burn out.

Thursday, 6 September 2012

More Mossy Thoughts

I've been thinking a lot about moss lately. My casual observations on my moss study have been very interesting so far this year. The small study green had zero moss when the study began this spring but had a history of heavy moss infestation in the past. Obviously this was the perfect spot to study moss. The only problem I've had so far this year is that almost no moss has developed on the putting green at all! What the hell?
Moss is losing the battle here in early May

Well as always I have a few thoughts and observations to share that could explain why. Who knows?

What I am thinking is that moss is affected by traffic or wear only at certain times of the year. Early this spring and summer I noticed that the existing moss on my putting greens was dying. It was black and basically being taken over by the turf. I was "wearing" my greens daily with a lightweight roller. By the time summer had arrived the moss had all but disappeared in the typical areas on my putting greens. I thought I had figured it out. Before this I had never seen moss disappear. Historically if I had moss it only got worse, not better.

Moss explosion on my irrigationally challenged
putting green.
Summer arrived and suddenly the rain stopped. Beginning late July the moss started to come on very strong. It wasn't coming on in the typical areas this time though. Instead it was developing in areas that the turf was thinning due to being either too dry or too wet. I actually found that the dry areas were worse than the wet which is contrary to most people's views so far. My upper practice green was and still covered in moss despite being grown in full sun. It has a very very very poor irrigation system that is gravity fed and maybe gets 20psi on a good day, even less when I'm pulling water for my irrigation ponds. Either way this putting green was constantly excessively dry and thus the moss population exploded. I wasn't able to roll more than 1x daily as the turf was pretty stressed from the heat and as a whole was quite weak.

Back to my moss study green. Even though it has historically had serious moss issues I was easily able to keep it adequately watered this summer. The fact that it was grown in almost full shade made my job easier as the plant water use was much less that it would have been if it was in full sun. The average canopy temperatures were often 10C less than my other putting greens. Some areas were severely thinning due to the excessive wear brought on by rolling up to 8x a day and guess what? Still no moss. There is some moss on areas that aren't rolled ever and recently on the 1x daily plots. All other plots are free of moss. This suggests to me that wear definitely has some kind of affect on moss and that it's not just thinned turf that allows moss to invade.
Rolled 8x daily plot with 2hrs of sunlight each day. No moss despite
the thinned turf conditions.

What I would like to know is how moss is affected by traffic at different times of year. What is it's growth cycle? When is it the most vulnerable? Maybe the answer is heavy rolling in the spring and better control of soil moisture and light rolling in the summer. Who knows? It will be interesting to see how the moss population on my upper practice green is affected once the rains start back up and adequate soil moisture is once again reached. I am going to mark out a few plots on the green to compare as the season progresses with my normal daily rolling program.
Control plot left and 2x daily rolled on the right.

I am continuing the moss study and will keep it up until I figure this out, probably a few more years yet.