Essential Greenkeeping tasks for November include aeration, disease prevention and keeping the surface clear of worm casts.
I once commented that there are only ever two real problems in bowling greenkeeping; compaction and thatch, with the rest of the myriad problems we come across being merely symptoms of these Big Two. Lately, I've revised that thinking, as the more I see of ill treated bowling greens the more I realise that, although they are important, even thatch and compaction are only symptoms too. The trouble we face in greenkeeping is that the industry wants us to treat symptoms. If we treated the root cause after all, we wouldn't need to buy half as much stuff! But before we get too carried away, let's have a recap on what bowls green compaction actually means.
Over 37 years of greenkeeping and teaching greenkeepers I have come to notice that bowling green performance comes down to just 3 major characteristics. Sounds easy then, doesn't it? Well it actually gets even easier when you identify the one key problem that contributes more to poor bowling green performance than any other.
Green Performance Explained in terms that show the multitude of characteristics of turfgrass plants and their environment that work together to make up the bowls green eco-system. By working in harmony with this eco-system, greenkeepers can shorten the learning curve on turf surface performance dramatically.
The relationship between sand and bowling green performance has become a thing of legend with the majority of clubs still throwing more sand on their greens every year, despite a worrying trend showing poorer and less predictable green performance due to problems like Localised Dry Patch and excessive thatch. It seems that for many clubs the dots aren't being connected between too much sand and poor performance. In this article I will explain the fundamentals that greenkeepers must keep in mind with regard to their bowling green soil.
We are familiar with the concept of our grass plants being composed mostly of water (75-85%), but what else is in a grass plant? The answer is that the dry matter of the plant is made up of a mix of 16 elements, commonly referred to as the essential nutrients. We describe them as essential because the plant can’t exist or complete it’s life cycle if any of these nutrients are lacking to any great degree.
Bowling Green Nutrition
Some of these elements are used in bulk by the grass plant. These are Carbon, Hydrogen, Oxygen, Nitrogen (N), Phosphorus (P), Potassium (K), Calcium, Magnesium and Sulphur. Some others like Iron (Fe), Manganese (Mn), Boron, Molybdenum, Copper, Zinc and Chlorine are used in smaller amounts. I’ve added the chemical symbol for the ones we commonly see on fertiliser bags.
A large part of this dry plant matter is made up of the three big elements Carbon, Hydrogen and Oxygen. In my introduction to Photosynthesis we saw that the plant takes Carbon (CO2) and Oxygen directly from the air by absorbing them as gasses through the leaf stomata. Last time we looked at Osmosis, the process used by our grass plants to take up water (H20) from the soil and this is where the Hydrogen (H) comes from as well as more Oxygen. The plants can always find an abundant supply of these three elements and if the day comes when they can’t, then we won’t need to be worried too much about how the bowling green looks!
The remaining 13 essential nutrients are accessed via the soil from 2 main sources, but regardless of the source, the grass plant can only absorb these nutrients once they’ve been dissolved and contained within the soil water, more accurately referred to as the soil solution as it isn’t just water anymore.
One source of nutrition is the process of decomposition that happens when plant tissue dies. This organic (carbon rich) material is broken down by soil organisms and micro-organisms and returned to the soil as readily available plant nutrition in the soil solution. This is why the bowling green needs to be considered as an eco system; nothing happens in isolation.
As we saw, nutrients can only be accessed by the plants if they are able to be taken up by the plant roots in the soil solution, but many of the essential elements needed to complete the grass plant life cycle are securely tied up in the soil minerals. These are made available by the slow weathering of the minerals by rain and wind and are washed into soil solution where they are available to the plants. However, the majority of soil nutrients are bound up and unavailable in what are called insoluble compounds.
To be accessible to the grass plant roots, the mineral and organic nutrients must be broken down to their simplest forms called ions and some of these are negatively charged (anions), while others have a positive electrical charge (cations). The most common form of Nitrogen used by plants is N03– which is an anion due to its negative charge, whereas Calcium is taken up as Ca++ which is a cation due to its positive charge, notated as two + signs in its chemical symbol.
These plusses and minuses are important in soil chemistry and in the relative success or otherwise of our bowling green maintenance. More + signs in the chemical symbol for any ion means a stronger bond to the soil colloid, the name given to the negatively charged clay and humus particles in the soil which hold on to cations and stop them from leaching through the soil. Incidentally, this is one reason we need to apply Nitrogen frequently as fertiliser; it’s negative ions are easily leached out of the soil by rain as they aren’t bound to the soil colloid. It also explains why it is futile to double up on fertiliser applications in the hope of a better result.
Before they can be made available to plants as ions in soil solution between 15% to 25% of the essential nutrients need to be dislodged from the soil colloid by an ion exchange and the relative ease or difficulty of this in a soil is called the Cation Exchange Capacity (CEC). The CEC is simply a measure of how many exchange sites exist on the colloid.
Now here is another of those wonders of nature that is difficult to appreciate when you’re looking out the clubhouse window at that square of grass. The root hairs of the grass plants release hydrogen ions (H+) and when these come into contact with the soil colloid, they each take up a place on the colloid, breaking or weakening the colloidal-nutrient bond of one of the other nutrient ions. Each + in a nutrient’s symbol is equivalent to one exchange site, meaning you need 3 H+ Hydrogen ions to knock a Fe+++ Iron ion off the colloid and into soil solution. Once these nutrients are knocked free they become more available to the plants, where they are taken up in soil solution through the root hairs.
Hydrogen ions H+ are at the very heart of another important soil mechanism called pH, but that’s for another day.
Next time we will look in more detail at the physical construction of the soil and find out why we need to be more thoughtful when considering top-dressing.
Cure Localised Dry Patch on Greens with this step by step guide to dealing with hydrophobic soil in bowls greens.
I've had a lot of requests to supply a general set of recommendations for winter maintenance for bowling greens. Although the full program for any green should be based on a thorough inspection and soil analysis, there are some general rules you can follow. I've also put together a suggested package of materials to help you apply this program more easily.
In parts 1 and 2 of this series on how to fix your bowling green, we discussed the process and importance of taking regular soil profile samples and discovered what the soil sample can actually tell us about the condition of the green. In part 3 John links this to demonstrate why each of the visual signals from the soil sample point clearly to one or more of the multitude of issues we experience on poorly performing greens. From disease outbreaks to skinning of heads and bad runs on rinks, the humble soil profile sample can tell us a lot about where we're going wrong and point to the answers that will help us create a performance bowling green in the near future.