Grasses, Irrigation & Wetting Agents

So far, we have covered the soils that turfgrass grows in and its maintenance, plant nutrition, and how to maintain the turfgrass with various machines.

We will have a look at the grass species we have here in Ireland. Also, with temperatures starting to rise we could soon have a hot summer period or a dry spell, so we will look at our irrigation and watering practices, as well as chemicals such as wetting agents that can help us maintain good moisture levels without over watering the turfgrass. The following topics will be covered:

  • Cool Season Grasses
  • Seed Heads & Plant Growth Regulators (PGR’s)
  • Root and Shoot Seasonal Growth
  • Plant Water
  • Drought Tolerance
  • LDS (Localised Dry Spots)
  • Wetting Agents
  • Irrigation Water & Practices
                                                            Cool Season Grasses

There are warm season and cool season grasses. Both types have their own different parameters for when and how they grow. Here in Ireland, we have cool season grasses, these would primarily be, Meadow (Poa/blue grass), Bent, Fescue and Rye species of grasses. The most commonly found on our pitch and putt courses would be Meadow/Poa. To give an indication between warm and cool season grasses, in a warm region like Florida Meadow/Poa would be classed as a weed.

In golf, the most desired species for a green would be bent or a mixture of bent and fescue but some golf courses successfully maintain Meadow/Poa greens as well. The grass you find on your course will depend on where you are geographically, for example fescue would be more a coastal species, found on links courses. For us in Dublin, Meadow/Poa is what we are generally stuck with, unless you wish to begin a programme of overseeding using bent and fescue. Different feeding programme would be required for this. The other option is buying in bent and fescue sod if renovating a green, which we had some success with for a number of years in Old County.

The parameters for germination and growth of cool season grasses are, slow or little growth at 0 degrees, maximum upper limit of 35 degrees, optimum growth at 15-25 degrees. Each species of grass has their own characteristics which are good for identification purposes.

Meadow/Poa

It has a shallow root system, it will have yellow foliage when stressed or there is a water shortage. Our mild-moist climate suits Poa as it does not like extremes and is intolerant of cold, heat and drought. It has a boat shaped tip leaf.

Bent

Bent is a highly stoloniferous grass meaning it grows horizontally, these runners or stolon’s (overground stems) is a reason thatch forms in this species. It has a high shoot density, and has a very shallow, dense fibrous root system. It has a pointed leaf tip.

Fescue

The leaf is small, narrow and needle like or barrel shaped. Great for colour but not for wear. Has a great drought tolerance.

Rye

Has a broad flat leaf and is a landscape grass used on pitches, parkland and tees and fairways of golf courses. It is resilient to wear and tear and is a tough grass.

Have a close look to see can you identify what species are dominant on your course from the descriptions above.

                                        Seed Heads & Plant Growth Regulators (PGR’s)

As Meadow/Poa Annua grass is a very dominant species of grass in this country and we deal with it quite a bit, we will cover a major problem that occurs with this grass, seed heads. In Spring you will have noticed that your low mowed Meadow/Poa greens will go to seed, they will have white seed heads. For us this causes problems such as, from a playing perspective the greens become slow and very bumpy, visually they look terrible, stalks and white seed heads can be seen across the surface.

Thankfully, we have options to deal with this and minimise the problem. The first is from a cultural point of view, we can scarify/verti-cut or groom the tops of the heads and remove them. The groomer is an excellent tool for this because it is not evasive like scarifying/verti-cutting. The brush on the front of the greens machine which we covered previously is also great for this. The brush like the groomer, will stand the stalks and seed heads up just before mowing. Seed heads also give you a good indication of how much Meadow/Poa grass you actually have in your greens.

The second option is a chemical solution, plant growth regulators (PGR’s). There is a lot of science behind these, so we will just jump straight to their purpose. Primo Maxx would be one of the most well-known brands of PGR, it is designed to help with cell elongation in grass, in other words get roots growing deeper into the profile which of course leads to a healthy plant. PGR’s also help with preventing the effects of drought by making the sward (coverage of grass) denser, another way of saying it thickens out the coverage but without increasing growth rate, in fact it does the opposite, it slows it down so that you will not experience flushes of growth which in turn reduces the frequency of mowing. One major advantage is it supresses seed heads in Meadow/Poa Annua grass as it reduces the growth spurt. Ask your supplier about PGR’s, they will advise how to incorporate it into your maintenance programme.

Typical view of POA Seedheads
PGR Primo Maxx

Root and Shoot Season Growth Pattern

Apart from the different grass species, the biggest difference between cool and warm season grasses is there shoot and root growth patterns. This is important when applying fertilisers as you have an indication when there will be spurt in either shoot or root growth.

Below shows the seasonal pattern of shoot and root growth for our cool season grasses.

Plant Water

Water comprises 80-85% of the weight of a grass plant. Supplemental water is needed to maintain quality in the turfgrass. Plant water is needed for nutrient uptake and transpiration which helps cool down the grass leaf. Transpiration is water movement through the plant. This is done through the stomata, which a very small pores on the leaf. As these pores open evapotranspiration takes place. Evapotranspiration is how much water the plant uses. Roots absorb water from the soil and transport it through the shoot to the xylem. It then evaporates from their surfaces and leaves the plant through the stomata. This keeps the leaves cool.  Cool season grasses do not like high temperatures.

You need to be aware of your soils ability to drain and hold water. As well as knowing your turfgrass root length. If your roots are 6 inches deep, you will need to get the water down that far if they are only down 2 inches, you will not need as much water.

Drought Tolerance

When we get extremely warm temperatures and periods of warm weather grass is very resilient. When a water deficit occurs in the plant, some can tolerate it. The plant will close the stomata to reduce the water loss through transpiration.

Symptoms of drought in the plant will be, curling of leaves, foot-printing (when you step on the grass, then take your foot away the footprint will remain), wilting and finally death. Factors that will determine drought will be temperature, relative humidity, windspeed and light intensity.

From a pitch and putt perspective we can protect our greens by irrigation, by increasing the height of cut, reduce the frequency of mowing and in an extreme situation you could keep the green covered with a large sheet to be pegged several inches of the ground. This could also be done for bad areas or sections of greens. On some golf courses large fans are placed greenside to lower the temperature.  We must reduce the stress on the plant as quickly as possible.

Footprints are a symptom of drought

LDS (Localised dry spots)

A localised dry spot is when the soil repels water. Water cannot infiltrate the soil, it has become temporarily hydrophobic (repels water). The water lies or pools on the surface. The turfgrass will turn a brown colour, when this happens the water reacts with the soil, the particles get coated with a waxy material which water cannot get through. Cycles of wetting and drying make it worse.

To cope with LDS, avoid allowing soil to dry out, topdressing can be done, mixing hydrophobic soil with unaffected soil/sand. Pencil tinning aeration along with wetting agents is the best practice. By pencil tinning and then irrigating the turfgrass, will allow the water to infiltrate the soil and get down to the roots, which in turn will allow the water to be taken up by the roots and moved up through the plant. The stomata will then reopen, and transpiration can then restart.

We have all seen this on a pitch & putt course, LDS, look closely and you can see the pencil holes

Wetting Agents

Wetting agents or surfactants are a chemical used to help water filtration rates through the soil. They do this by lowering the surface tension or by breaking down the waxy substance that we spoke about above. A way to explain surface tension is how water when spilled on a kitchen countertop just spreads across the counter. This is the same as what happens with LDS. You get surface run off, the science is to break the surface tension effectively, penetrants need to be small molecules that move fast within water droplets. They also need to be able to pack tightly at the surface of the liquid to break surface tension and help the water spread. Science bit over. Wetting agents break down the waxy substance build-up on the particles, in particular sandy soils but also in other soils.

Wetting agents were originally designed for LDS, but over the years have become a vital part of water management practices in golf clubs around the world. Where wetting agents can help us as pitch and putt greenkeepers is with clay soils that hold water very easily, which as we have explained causes many problems such as disease and poor playing surfaces, they can help filtrate and regulate the water all year round and not just when we get a warm summer. I highly recommend including a wetting agent in your greens chemical and feeding programme. They can be applied in both liquid and granular form which is great for pitch and putt. They can regulate the moisture in the soil, keeping enough for the plant to grow but not too much as to saturate the profile. They are normally applied monthly from April to September. The version I use from Cropcare is Aqueduct flex granular, it is expensive, but it is used at a low application rate.

Another type of chemical related to this subject are Soil Penetrants. The purpose of these is to help water penetrate and percolate through the soil, to increase moisture in dry soils and increase soil oxygen in hydric soils. I recommend asking your supplier what products they advertise. Again, with Cropcare I use Dispatch, but this is a sprayable. I am looking into using Aqueduct flex all year round because it is a granular, but I must see how reliable it is in the Autumn and Winter months.

Irrigation Water & Practices

For me one of the biggest problems in pitch and putt course management is how much water is applied to greens. Goes without saying, we live in Ireland, we are defined as a temperate oceanic climate. This means we receive warms summers and cold winters. What we can agree on is we can be a wet country even in Summer months. We get rain on average 151 days per year here in the East and 225 days in the West, yet the use of irrigation can be extremely high among course managers in pitch and putt.

One saying we have probably all heard is, “greens are watered to keep the grass alive and not to make pitching easier”. Simple fact is that this is true. I hope by now you have seen the number of problems that too much irrigation and rain can cause in trying to maintain healthy, firm and fast putting surfaces. Grass does not need water every day. As we have seen, soil and sand to a lesser extent hold certain amounts of water for root uptake, on top of this we have covered how wetting agents also help to regulate moisture content in the soil.

So, all I can say is it is up to you to monitor your green, there are moisture meters, but these can be extremely expensive. There are only a few times a year that irrigation is necessary, after applying a granular product, after applying a wetting agent, and if your greens are starting to go a yellow or brown colour in warm conditions or if windy conditions are drying the surface out. Be mindful of the amount of water your greens are getting.

Running Times

The other massive problem is the length of time irrigation sprinklers are left running for. Ever irrigation system will be different from the number a heads on a green, the nozzle size of each head, the pressure the system is set at, to the pipe size under the ground will all contribute to the amount of water going on the greens. So, it is not a simple case of saying leave the sprinklers on for 5mins a night and that will be accurate. An example I can give is in Old County in the very warm summer of 2018 we had the system set to come on twice through the day for 7 minutes, this was on sand based greens the water will percolate through quicker than clay and the temperatures were between 20-26 degrees.

The warm conditions are not the problem I see, we have relatively mild conditions and greens being watered just because it has not rained in 3 or 4 days, and then receiving maybe 10-15 minutes and set twice in the day. This is where the problem lies, ask the question was the grass showing signs of drought? would 3-5 minutes of water have been enough? Would one application have been enough? These are questions only you can answer. It is a learning process which we must go through.

When to irrigate?

There is plenty of differing opinion on this, during a warm day, some of the water will be evaporated, so they will irrigate at night with the timer. But, if you irrigate at for instance, at 10pm or 1am, that means the water is sitting on the surface for approximately 8-10 hours and if the next day is overcast the water will still be sitting there by noon the next day. That brings us back to trying to keep the leaf as dry as possible for as long as possible to avoid disease and thatch build-up. It really is a vicious cycle!!!!!!!! Personally, when I can, I will avoid watering at night, I occasionally will set the timer to come on early in the morning about 7am-8am if its needed other than that, I just set for late afternoon, just enough time for the water to infiltrate the soil but not to be lying all night. One thing I must stress is, I feel limiting the amount of water that goes on is more important than when it goes on.

Leaf Surface Area

One thing you must be aware is the amount of water taken up by the plant is determined by surface area of the leaf. This the size and shape of the leaf which determines the number of stomata on the leaf. The best way to explain is, if you take a blade of grass of a green and take a blade of grass of the rough/fairway, the blade of the green will obviously be small which means it will require less water. So, if we cut our greens at 5mm and the rough/fairway at 30mm, it will require 6 times the amount of water. Would you leave a sprinkler on the rough/fairway for 3 hours, the answer would be no, so why would you leave a sprinkler on a green for 30minutes which I have seen happen. Try and cut down on your irrigation, if then green is browning up, water it but do not saturate, the soil will only be able to hold so much until it reaches its capacity, again remember we only need 25% moisture for a healthy turf. Just another point to mention, with Fescue grass, when it experiences warm or drought conditions, it curls itself up which reduces its leaf area size which in turn reduces the amount of water required.

Hand Watering Small Stressed Areas

Syringing is the term used on golf courses for how greens are hand watered. This is when a small amount of water is applied to the top of the turf to evaporate and cool down the grass. This is best done at the hottest part of the day. This allows the stomata to open and the process of evapotranspiration to continue. If you have manual watering points on your course this is a way of treating a dry area or part of a green rather than watering the whole green when we say maybe just the corner or edge of the green requires water. Hand watering is also good if you have poor sprinkler coverage.

Also, on irrigation water, it can be a good idea to get it tested, if you are irrigating a lot, the irrigation water can be carrying chemicals or an abundance of certain nutrients that over time can affect your turfgrass. An example of this would be, if high concentrations of Aluminium and Manganese are in the water, they can be Phytotoxic (toxic to plant growth) in acid soil. Also, Salinity is the salt concentration in water, Meadow/Poa grasses are very sensitive to salinity. Irrigation water can also contain tiny particles of clay, silt, algae, fungi, and bacteria, so no harm in having it checked. It is also the time of year to check and run your system to make sure it is running properly and that the pressure is fine and there are no broken or leaking sprinkler heads. No point in waiting until the dry spell comes, turn on your system and realise you have a problem, the greens could be severely burnt by the time the problem is rectified.

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