If you tried to pass this stateme
nt off as a little-known piece of valuable professional advice, someone would probably laugh at you. Yes, we all know that grass needs water. All plants need water. Even the least agronomically apt person can tell you that grass needs water. My point is not to outline the moisture requirements of grasses, but is instead to provide some information on water being used to encourage carbohydrate production and transpiration. In essence, this is about syringing practices.In those climates where we manage cool season grasses, also known as "C3 grasses", we all know that "cool season" can be a misleading term. While, yes it is cool in the spring and fall, it can be sweltering in the summer months. Of course this does not ring true for every region which cool season grasses grow in. For
the purpose of this post, let us focus on those regions where summer temperatures may exceed the comfort level of the cool season grass plant. The cool season grasses typically prefer a temperature range of 60-75F (or 16-24C). When temperatures exceed this range, negative effects on the plant begin show. As you can see by the picture on the right, when the temperature begins to rise, the growth of the plant slows drastically. This bi-modal growth pattern is almost entirely due to the way that cool season plants photosynthesize.When the cool season grass plant is subjected to temperatures above its desired range, the way that the plant creates its food becomes less effective. The C3 grass receives its carbon molecules (which are used to make sugars and provide the plant with energy) by using an enzyme called "rubisco". This enzyme is most effective when operating between 60-75F, but when you ask it to work in the heat, it gets "sloppy". When it gets sloppy, it loses the ability to discern oxygen and carbon molecules. Imagine that a jar is filled with two types of marbles and you reach in and pull out a handful. The mixture of marbles in your hand is a way to visualize the way rubisco operates in high temperatures. Now the problem with oxygen is that is does not make a very viable sugar. If the plant tries to use oxygen in the place of carbon, it is pretty much "dry-firing," and is expending energy while gaining nothing. This process is termed "photorespiration" and is in no way beneficial for the plant!
The heat also affects the rate at which a plant transpires, or releases water molecules. This process is in some ways comparable to the way a human sweats to regulate temperature. When the plant finds itself getting too hot, it reduces its transpiration rate by closing pores in its leaves called "stomates". This closure is supposed to conserve the plant's moisture, but it leaves the plant with the inability to effectively cool itself. In the wild, this strategy for moisture conservation serves the plant well because it needs to be as thrifty with its H2O reserves as possible. However, in the intensely monitored growing conditions of a golf course, a deep and infrequent irrigation regime should ensure that the plant is able to access an adequate amount of H2O at any given time. The closure of stomates and subsequent halt in transpiration can lead to mortality of the grass plant if we do not find a way to get the plant to begin transpiring again.
The application of small amounts of H20 is known as "syringing."Syringing practices, when correctly employed, can be of huge importance to the quality of grass in high-end turf maintenance. As discussed earlier, heat can disrupt the ability of the plant to make food and can leave the plant vulnerable to desiccation. Syringing modifies the tissue temperature of the grass plant in an attempt to give it an edge when subjected to high heat. In this period immediately following the application of water (again, only a mist is needed) we see the plant begin to transpire once again, thereby cooling itself. Also, the effectiveness of rubisco is increased and the plant is able to generate food more efficiently. Anyone who has seen the effectiveness of an accurately timed syringing practice can attest to it's importance in the repertoire of skills a turf manager must possess to be successful in this industry.
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