This got me thinking. Uh oh.
At this time there was very little bentgrass left on my greens. They were almost 100% poa annua. I was in the process of making big changes to my management techniques. The use of a moisture meter allowed me to keep moisture levels controlled during the optimum growing season. I changed over to the MLSN fertility guidelines and my fertilizer rates were changed to be based on the temperature based Growth Potential. I changed the way I mow, cultivate and almost every other aspect of the putting green maintenance.
I started using a moisture meter in 2008. All of a sudden I wasn't guessing on soil moisture levels. Although I wasn't precisely controlling moisture similar to how they do on Tour I was able to keep the greens significantly drier. Some people say that in my climate (West Coast of Canada) it is impossible to keep the greens dry as it rains for half the year. The difference I think is that when temperatures are the most conductive for turfgrass growth I had full control of soil moisture levels. Back when I was guessing the soil moisture we probably consistently applied double the required water for healthy turf growth.
Since I was using growth potential fertility most of my fertilizer applications are made in the summer, again when I have full control of the soil moisture. I wasn't pushing turf growth in the early spring and fall like I used to. Based on my observations I really think that pushing growth during these cool wet times is a big contributing factor to the success of poa vs bentgrass. We are often too eager to get things moving in the spring and I think this causes all kinds of issues. During these cool wet periods the bentgrass looked fantastic and the poa looked hungry, very very hungry.
|Mid spring the poa is still hungry and the bent grain is starting to show|
|Furry bent in early spring doing well under the low/no fertility|
|A rather extreme case of Cyanobacteria has thinned the poa a bit too much.|
Using Primo through the winter has probably also helped. Keeping the higher metabolizing poa at bay during the cool parts of the year when poa is known to make advances can't be a bad thing.
I have also stopped verticutting my greens. I asked myself why I was doing this and made some measurements. It really made no difference playability-wise and it also contributed to disease spread as observed in this post this spring. There is a lot of talk about the disturbance theory and verticutting only allows poa to establish and spread. I had never verticut deep enough to remove much thatch and honestly thatch on my greens isn't much of a problem. I think this is due in part to my change to temperature based fertility and daily rolling. If conditions aren't waterlogged the soil microbes can better do their job breaking down the soil organic matter. Matching fertilizer applications to temperature might match thatch production to thatch decomposition more closely.
We have been rolling daily and mowing every other day for almost 4 years now. This might also contribute to the bentgrass domination as per the disturbance theory.
|bentgrass is very visible during the winter frosts. The poa is yellow and not very happy.|
|The coarser bent now consistently covers most of my putting greens. The grainy turf covers over the finer poa plant.|
The thinking was this; may the best grass win. With such a drastic change to my management techniques I wanted to see what grass species would do better and provide a bit of insurance in case one species decided to check out. Of course poa will always be here but if my new management techniques favored the bentgrass I want there to be as much bent out there as possible.
On some greens the bent has done better than others and as time goes on I will shift my over-seed rates higher on the greens with less bent and probably stop over-seeding altogether on the other greens that have a good population of bent established.
|Bent has quickly become the dominant turf species in a few short years. Only speckles of poa remain on this green.|
I have had a lot of people tell me that growing bent can't be done in my climate. "Grow what grows." My answer to that is how long have we been completely guessing about what we are doing? How long have we been using moisture meters? Are we applying fertilizer to suit the actual turf needs based on temperature? Are we applying pesticides preventatively? How often do we verticut? How much phosphorous have we applied to our greens this year? Why? Are all our fertility inputs actually needed?
It took 20 years of over-watering, over-fertilizing, and overuse of pesticides for my greens to become almost pure poa annua.
I'm not against poa. It makes for really nice greens. It just so happens that the changes I have made to reduce inputs and eliminate waste and guesswork has lead to conditions that favor bentgrass. If that is "what grows" then it just makes sense to grow it.
My goal isn't to have a pure stand of bentgrass. None of my surfaces are managed for pure perfection. I have some weeds, but use no herbicides. Some disease, but use few fungicides. I try and manage for a good playing surface with the lease possible inputs, especially chemicals. With this philosophy and management style I expect that eventually bentgrass will be the dominant turf on my course. It won't be pure. I will always have a lot of poa but I will be able to further reduce my inputs of water, fertilizer, and pesticides without fear of catastrophic green failure.
|The bare minimum. Mow, roll, fertilize, water, solid tine cultivation. Not perfect but the price is right!|