Friday, 4 August 2017

Don't knock it till you try it (or don't try it). Afternoon watering.

Some might call this overwatered, but the VMC is right where we want it and the greens are nice and firm. Watered by hand each morning during the heat.

This week I quoted a tweet by the USGA and started a shit storm on twitter.

I love it when people get riled up about grass!

The reasons I asked the question "is there a good reasons why sprinklers are running during your round" was that for the longest time I thought I needed to water in the afternoon to cool down the grass or to keep it alive to live another day.

It turns out that this wasn't the case for me but it was taught in school that afternoon watering was an essential practice to provide good golf course playing surfaces.

The article I posted was actually really good and took a good balanced approach at promoting what we do is not necessarily bad and outlining the very good reasons why you might see sprinklers running during the day on a golf course. Hell even I have to do it sometimes when things break!

It has been proven again and again that afternoon watering does little to cool the plant so if you are doing it, it is to replenish water in the soil to avoid some pretty specific issues that some courses might face. Thankfully, my course isn't one where we need to water during the day unless a pipe breaks overnight.
It was pointed out to me over and over and over and over again that just because I don't need to water during the day that others might not have that luxury. I totally get that, it's pretty obvious. What is true on my first green isn't even true on my second! Everything is highly location dependant in our industry. There is nothing universal in our industry. What concerns me is that I bet a lot of people who currently water during the day, could probably get by without it.

For the longest time I thought it was needed on my course and I would water every afternoon on a hot day. That was back before I really had any idea of what I was doing. That last sentence is kind of paradoxical as the more I learn, the less I feel I know. Hmmmm

Then it was pointed out to me that maybe daytime watering wasn't necessary.

So what did I do?

I immediately sent Micah an angry email telling him how wrong he was.

Actually, no that is not what I did.

I tried it out to see for myself. And guess what, he was right (as usual). It turns out that on my property and in my climate with my type of grass (almost 100% poa at the time) I didn't need to water at all during the day. If we had enough water in the soil we didn't need to add more no matter what time of the day it was. Boy did this save me a lot of time.

It also reduced the amount of disease on my greens (and need for corrective fungicides). There's nothing better than warm and constantly wet for turf disease production from what I've seen. It puzzles me when we work so hard to remove the dew in the mornings in an attempt to dry things out and then go and purposely make the grass wet again. Either way I kind of think the whole drying grass out practice isn't worth it either so who knows?

Don't knock it until you don't try it.

I try to take this approach to everything. I've tried preventative fungicide applications, I've tried designer fertilizer programs, I've tried deep and infrequent watering (I can't make it work on my soils with my irrigation system), I've tried every stupid practice and gimmick there is to try. Hell I even tried compost tea once 😄 I will try anything once and will make observations and decide if it's right for my situation.

What I caution those who were so against my questioning of daytime watering is to know if they tried not watering in the day or not. Don't try it for me. Try it (and anything you read about) for you and see if you can adapt it to your specific circumstances to make improvements.

Smoke from wildfires dampen the record breaking high temperatures to only 105F.
I'm sure those who were adamantly against no water in the day had tried it for themselves. It's a pretty easy thing to test afterall. Simply don't do it for a day and if the grass suffers more than usual, go back to the way your were doing it before. If nothing bad happens, try it again, and continue this process until one day, 5 years later you haven't watered in the afternoon even once despite 2 record heatwaves and droughts.

I know that there are plenty of circumstances that require daytime watering as was outlined in the USGA article. Please don't hate me for suggesting that it might not be needed, because guess what? It might not be for everyone....maybe even you 😊

There I go again....Look at what I can do with all the time I save not irrigating during the day!

Wednesday, 19 July 2017

Can I use clipping yield to prevent disease this September?

Managing turfgrass disease with the goal of reducing or eliminating pesticide use takes a lot of planning, careful observations and fine tuning. While we are currently in the middle of the summer turf disease cycle, I am already planning ahead for the most difficult time of year that I face when managing turf disease, September.

September has always been a challenging time of year for me as we transition from managing for dollar spot to managing for fusarium patch. These disease are seemingly polar opposites when it comes to IPM strategies. High nitrogen reduces the impact of dollar spot and low nitrogen reduces the impact of fusarium patch. During the transition I am forced to pick a side and often lose the battle on both fronts. So far in my career, September is the only month that I have not been able to get through without the need for a corrective fungicide application for either dollar spot or fusarium patch.

Last month I made an interesting observation about clipping yield and fusarium patch. Basically the greens with the highest clipping yield had the most disease. What was even more surprising to me was that my historically bad green for disease was clean of disease as it had a very low clipping yield. Hmmmm

It is well documented that different rates of nitrogen can have impacts on these diseases but if it was this easy, we wouldn't need fungicides.

My observations last month have got me thinking about disease management and I think clipping yield might be the missing link for me because it is the sum of all things that influence plant growth. It paints a very clear picture of what is happening to your turf.

I have always treated all my greens the same when it comes to fertilizer. If one green gets some fertilizer, they all get it. This was until I started measuring clipping yield on each green individually. This understanding of how each green was growing compared to the other greens allowed me to make further educated observations that I wouldn't have been able to otherwise. This combined with the wildly varying fertilizer rates on my dead greens this spring has allowed me to compare the differences in growth rates to disease activity on my course. It's like a huge science experiment.

As you can see from the tweet above, there is a sharp cutoff for disease pressure for different rates of nitrogen applications for dollar spot. I have a feeling there is a similar cutoff for fusarium too. Is it the nitrogen, or the resulting growth rate from nitrogen application that is making the difference?

On my greens that have received relatively high amounts of fertilizer there is no dollar spot or anthracnose, but they had a lot of fusarium last month. On the greens that have received regular low rates of fertilizer, there has been no fusarium since last November but slight incidences of both dollar spot and anthracnose.

Before using the growth potential formula to predict fertilizer rates I was fertilizing all wrong for my climate. Once I started using GP I instantly noticed an improvement in the disease pressure on my course.

During the challenging month of September I am faced with both disease simultaneously but here's the thing, they don't happen on the same greens. Some greens get fusarium, and some get dollar spot. Why?

While I don't have individual green clipping yield data going back more than 1 month I do have data going back years. It seems to me that the variation in growth rates from one green to another are the cause of the varying disease pressure that I observe. Different greens were rebuilt at different times, have less sun, differing drainage characteristics etc and these all have impacts on how the grass grows and how soil microorganisms function and mineralize the soil organic matter.

Using the numbers I measured last month and in previous years in relation to disease pressure I could possibly assign target yields for each disease. Of course I don't expect it to be as simple as this but if I can understand the relationship between yield and disease pressure maybe I can combine this with all the other things I have been trying to be even more successful.

For fusarium the yield that seems to correlate with increased disease pressure is about 1.5L/100m^2 per day. Anything over that and fusarium disease pressure is essentially out of control when temperatures are mild.

Looking back on previous years' overall growth data it correlates almost perfectly with need for a fungicide. When growth rates go over 3L/100m^2 during periods the spring and fall, I require a fungicide. All the other things I do to culturally control fusarium aren't enough when growth rates are this high combined with mild temperatures.

Last year I made it through the Month of May without a fungicide for the first time ever. Growth rates never went over 1.5L/100m^2/day in May 2016. This year, only those greens that had a growth rate over 1.5L/100m^2/day in May needed a fungicide.

Take a look at the growth rates in September 2016.

DateClipping yield L/100m^2

Last September I needed a fungicide for fusarium on September 4th. This observation combined with my recent observation made on individual greens leads me to suspect that I need to aim for a clipping yield below 1.5L/100m^2/day by the end of August. It will be interesting to monitor disease and compare it with yields in the next few months.

Of course this assumes that I have that much control over growth rates and that my numbers are correct and that growth rate has an impact on fusarium patch disease severity. It also doesn't account for the different susceptibilities that poa has to disease vs bentgrass. Let's assume that all these figures are for poa.

So what about dollar spot? My numbers suggest that greens that have a yield greater than 2L/100m^2/day have less dollar spot.

This brings me back to my plan of attack for this September. Recently I have been varying rates of fertilizer on each green to try and achieve a more uniform growth rate across all my greens. The results have been quite successful. Despite the varying growth rates the Coefficient of Variation (Cv) has been dropping which signifies more consistent yields from one green to another.

So now that I am measuring individual yield and fertilizing based on these yields, I hope that I will have more success managing both of these diseases in September. I will aim to keep yields above 2L until mid-August when I will transition to lower yields as the month closes.

I think that if this works I will need to work towards a better understanding on all the things that influence growth rates and how I can manipulate them with the relatively few tools available. Also note that I don't think growth regulators will have a positive impact. If you use PGRs I hypothesize that the growth rates will be relative to one another but who knows.

The chart below illustrates how I have manipulated the growth rates of the greens that received a lot of fertilizer this spring to speed recovery from winter damage. By only fertilizing the greens that have low clipping yields I have been able to make the clipping yield more consistent across all my greens.

I think there is still a lot to learn but this gives me something to try and probably fail at which is what keeps me going. Here goes nothing!