Saturday, 23 November 2013

Growth Potential Fertility: After 2 years

GP finally = 0!!
Growth Potential Fertility (GP) is still a relatively new concept in turfgrass management. For the past 2 years I have been using it as the main method to determine rates and timing of fertilizer applications. If you haven't already read this excellent article by Dr. Micah Woods, I highly suggest you do otherwise this post won't make much sense.

I currently use GP to fertilize greens, tees, and fairways. My main motivation to use GP fertility is to reduce the incidence of disease and to reduce or eliminate any excess or waste in my operation. That is the main purpose of GP, to only apply as much nutrients as the plant needs at the correct times.

I have had quite a few questions how I use GP in practice. Here is a brief overview of how I use GP on each area of my golf course.

For Greens I apply simple soluble source nutrients weekly applied through my sprayer. Every Monday I check the forecast and from this I get the average temperature for the following week. This number is never 100% accurate but it's usually pretty close. I plug that number into the equation and it spits out the nitrogen rates needed for that week. I can then base the rest of my nutrient requirements off of the nitrogen. I apply in this manner from the beginning of March through to the end of October. I go every week because frequent light applications of urea are more efficient than infrequent heavy applications. The rest of the season is cold enough that a light granular app in mid October will carry the plants through the winter.

For tees and fairways I don't have the luxury of applying fertilizer to them every week. On tees I still use blended granular fertilizers with non-water soluble source N. What I use is the average monthly temperature for my area for the past 30 years. Again this number is usually nowhere near actual field conditions but it gives me a pretty good general idea of what to expect. I plug the monthly rate into the calculation and apply fertilizer to my tees once a month. For fairways I switched over to urea as my main nutrient source this season. I was going out every 3 weeks to spray wetting agents so I might as well apply my fertilizer at the same time to save time. I took the monthly GP N rate and multiplied it my 75% and that gave me my 3 week rate. For tees I applied fertilizer as long as the rates were high enough to be physically possible with a granular product. This turned out to be from April till Oct.

Now the above outline is pretty basic. I have tweaked my program over the past few years to better suit my site's specific needs. I have made changes to the GP calculation and have strayed from GP all together in some instances.


For my putting greens I have changed the optimum cool season turf temperature to 18C instead of 20C. This is because my putting greens aren't creeping bentgrass, they are annual bluegrass. It is well known that Poa is less tolerant of high temperatures and can require more fertilizer than other turf species. The adjustment to the equation gives me slightly higher rates of N but doesn't increase the total monthly maximum rate. 3.5gN/m/month is plenty in my opinion. I have always based my fertility program to balance plant health and incidence of disease. I don't want to apply more fertilizer if it is going to mean I have to apply more pesticides. For my grass and climate anything less than 200kg N/ha/ year will result in less M.nivale. To get a good number for your site I would suggest making a spreadsheet similar to the one below and play around with the number to give you a total annual N rate that your are comfortable with. This will give you a good place to start and you can fine tune from there.

My GP fertility calculator annual rates. This is what I use for long range
planning, not for weekly applications
You might have noticed the Civitas/PGR adjustment on the top right. What that is is a way for me to tweak rates based on Primo Maxx and Civitas applications. What I have done is run at 80% when I am applying Primo or Civitas as they seem to reduce the nitrogen requirements.
This is my weekly fert calculator. Plug in the temps and it spits out my tank mix.

Last season I had some greens that were severely damaged over the winter months. I also had some major drainage issues that I wasn't able to address until this fall. These greens required more fertilizer to keep healthy. My healthy greens only required 180Kg N/ha where my unhealthy greens required almost 200kgN/ha to aid in the constant recovery. If you commit to GP don't be afraid to stray from the plan. The really cool thing about GP, though, is that it gives you a really good way to compare fertilizer applications year to year. A 200% GP rate can be as small as 4kg N/ha/month difference in March or as big as a 35 kg N/ha/month difference in July! By keeping track of the GP and how you deviated from the GP you gain a very valuable tool to understand what you are seeing out on the course. If you aren't using GP yet it can be a valuable tool to compare your current fertilizer practices with GP and see how far off you are. Maybe it will help you make some correlations between fertilizer applications and plant health, or seeming lack of it. Here is another great articlefrom Micah Woods showing how reduce potassium inputs in the fall can result in a lower incidence of Grey Snow Mold. The GP fertility method lends itself perfectly to these observations as well.


This year was the first season I used GP on my tees. I was unsure how applying fertilizer with my new sprayer would work on my tees as they are very small and surrounded by steep slopes and rock walls so I chose to use a granular blend. For the most part this worked out pretty good. Because I wasn't able to apply rates as low with a granular as with a liquid. I wasn't able to apply the actual GP rates early and late in the season. I used a blend with a higher % of water insoluble nitrogen which seemed to work out OK.
These tees are hard to spray.
I was able to do a few test sprays on my tees this summer and it turns out that spraying them isn't that big of a deal. Next year I plan to use the sprayer early and late in the season as well as during Mid Aug-Sept to attempt to reduce the incidence of dollar spot. The worst outbreaks of dollar spot have always been where slow release nitrogen sources have been used. Urea packs a punch and makes a big difference. I won't be exclusively using the sprayer on tees, though, because I don't want to make that frequent of fert applications due to time.

Last year I noticed a green up response due to worm castings so this year I will apply a nitrogen punch at this time to help green up and out-compete weeds on the tees. I waited too long to apply fert to my tees this year and as a result there was an increase in clover and plantain. I am less concerned with disease on my tees in the spring so some extra nitrogen at this time shouldn't make a big difference to disease.


In the past I was never able to fertilize my fairways with a sprayer because we only had a pull-behind 200L sprayer and only had a 2wd utility vehicle to pull it. This just wouldn't work for my hilly course. This year I was lucky enough to get a 757L Toro workman spray system on a 4wd chassis. Instantly I was able to spray fairways.

In the past with granular fertilizer applications I was limited to the N release duration, and prill size for my application rates. With my mild season I wasn't able to get rates below 200kg N/ha/year which is quite high for fairways on native soil where the clipping are returned. I switched to a slower release N source last year to try and reduce my N inputs but had a way more dollar spot on my fairways. So much that in some areas I had almost catastrophic losses.

This year I took the advice of a few superintendent on Twitter who said they had been going out with straight urea every 2 or 3 weeks and hadn't noticed any difference compared to other slow release N sources. Of course N losses were my biggest concern using straight urea for longer durations. I trusted their experience and advice and can say that I wasn't disappointed. I chose not to apply any other nutrients as I had obviously been over applying them for the past 20 years!

Just like the greens I adjusted my GP fertility calculation to take into account that I was on native soils and was returning the clippings. I used 18C for an optimum temperature and then went out at 50%GP. This gave me an annual rate of only 80kgN/ha!

This was a significantly lower rate than I had ever applied and I was a little nervous. What I observed was nothing short of amazing. The fairways were more consistent, green, and disease free than they had ever been before. Of course there are other factors at play here but I was not disappointed in the least! The Urea seemed to last the 3 weeks except for a long hot dry spell in early August. Next year I will shorten my application intervals to 2 weeks in the summer. I will also apply an early season boost just like on my tees to help out-compete the weeds. I will also add in some iron sulphate in the wet season to try and help with disease and colour.

In the future I think there are still areas where I can improve. One of my biggest issues this summer was wet conditions and disease. These were combined with huge growth surges which I think were due to excess nitrogen in the soil from OM release. I think that regular (weekly) testing of available soil N would be a huge help to further fine tune the GP fertility for disease management but until a fast, easy and economical way to measure soil N is developed I am stuck guessing.

So that's about it for now. I have switched over the way I fertilize, have saved a ton of money, increased the quality of the course, and gained a better understanding and ability to compare inputs to the course year over year.

Global Soil Survey Fert Recommendation

I also want to give another quick plug for the MLSN and the Global Soil Survey. I have also been using the MLSN for the past 2 years and so far so good. The results from my soils survey this year concluded that according to the MLSN I should be able to get away with applying only nitrogen to my putting greens next year. I think I have solved the major issues with my greens so next year should be good fun. I am going to give it a whirl and see what happens. Stay tuned....

Friday, 8 November 2013

A Funny Story

So here's a funny story.

Last Tuesday the 28th of Oct as I was finishing up mowing fairways I took a pass across the approach of the first green just to see how it looked. The past 2 days had seen a heavy frost so I wasn't able to get onto the greens to have a good look. To my horror the entire green appeared yellow. "Oh shit! I've killed the greens.....again!!!"

The Saturday before I couldn't believe how great the greens looked. Everything was looking good going into November and the winter. I wasn't going to let what happened last winter happen again. Dead grass this time of year sucks to say the least.

So that Tuesday night I got no sleep. I was a nervous wreck. The next day I went out to check on everything and yep, I thought I had killed them.

I tried to figure out what went wrong. The Sunday before was a nice day and my weekend staffer assured me there wasn't any frost when he rolled. I didn't believe him or the pro shop staff. This had to be it or so I thought.

My next step was to review all of the products that I had applied to the greens over the past month. Maybe I applied a bad combination of something. A word of caution. No matter what combination of chemicals you punch into Google you will almost always be able to find someone who says it is lethal to grass or extremely phytotoxic. CRAP!

At this point I thought all hope was lost. What am I going to do now. I sent off that dreaded email to my boss outlining what I thought was happening. "I think I killed the greens again so....."

I spent most of that morning just walking the greens, feeling hopeless and sad. I felt crushed and had lost all of my passion for my work. As I was pacing I get a text from the Super down the road.

"how's it going"
"shitty, my greens are dead"
"what happened?"

We tried to figure it out over text message until he informed me that "4 turf techs will be there in an hour" He was bringing all the Supers on the Coast up to see me.

There's nothing better than looking at someone else's dead grass. It's always a good learning experience. No one likes to see nice greens, come on now.

My wife had also come down to the course to see what was up. I took her down to the greens. She thought they looked great. I didn't believer her. She doesn't know grass....

They supers showed up and I took them down to my dead green. The first thing they say is "you asshole, there's nothing wrong with these greens" They aren't perfect, I've had some issues lately with drainage and keeping the density up, but were , in their opinion, looking good. I didn't believe them at first. What I had witnessed was beautiful putting greens with a vibrant green colour almost overnight turn yellow. Nothing happens quickly to turf except die.

We toured the course. I tried to tell them how my greens were dying. They weren't buying it. "what a jerk, invite us down here to see some dead grass and all we get is this? Show off!"

I wasn't showing off, honestly. I didn't sleep a bit for almost a week. I was a mess, depressed.

When you put so much effort into something, thousands of hours. Your family has to put up with your long hours away. When the greens suddenly die all of that hard work and sacrifice was for nothing. A waste....

Oh, yeah, this is a funny story.

So after the visit I felt a bit better. I have a great deal of respect for my fellow superintendents and trust their judgement even though I was still convinced something was up (who knows it could still be). I actually slept a bit that night.
My dead green pic
I posted a pic of my dead green on twitter and also got some great advice. "they look great" "sometimes the best thing to do is nothing"
I now had some options, try and do something or do nothing. I knew enough to know that I was too emotional to make a sound decision so I put my trust in them and did nothing. It's not like I had a lot of other options this time of year.

I took 2 days off to go play with helicopters. I needed to clear my head and take a break.

Upon returning to work I wasn't so down on the condition of the greens. They were far from perfect but seemed to still be alive.

So I get a voicemail today from one of the Supers that came down last week saying "we figured out what's wrong with your greens"

I promptly called them back. Hey, I want to know too! I thought it a bit odd for them to have figured out what was going on a week later without actually stepping foot on the property.

CIVITAS! What I was seeing was a lack of Civitas. They figure I had become accustomed to seeing the artificial green from the Harmonizer pigments. Good God they were totally right! I had no clue what colour Poa actually was this time of year! They did because there weren't using it.

The Saturday before I noticed the yellowing I had cut the greens but was then unable to get onto the greens for a good look due to persistent frost and darkness. When I finally was able to get back on 3 days later the difference in colour was drastic. I must have removed most of the pigment during the cutting. Add the changes in my fertilizer program where I wasn't really fertilizing much this time of year. Two years ago before I started using Civitas I would apply quite a bit more fertilizer through the winter, until I came across Growth Potential. Now my greens really aren't that green, at least not compared to the colour of Harmonizer.

Talk about paranoid. Looking back it's quite clear how the effects of working alone, more often, without having the luxury of a second opinion blurred my judgement. The weather, darkness, and having to work more to cover all the days of the week by myself broke me down.

It also points out the biggest drawback of using pigments in turf. It takes away one of your best tools for assessing how the grass is doing. Your eyes. With the persistent artificial green I was unable to see the gradual changes as the season progressed.

Over a week has now passed and I feel a lot better about the condition of the greens. They've been better but they appear to be alive now haha.

If it wasn't for the help and concern of my fellow superintendents and wife I might have done something foolish to try and fix the greens. Working alone this time of year definitely takes a toll and it's really good to know that if I need help, it's there. Thanks guys.