Venting Greens

Root zone management is one of the most important objectives when growing cool season grass in the transition zone. As summer heat and humidity build-in through June, July and August, a grass plant's photosynthetic potential lessens and its need to respire increases.

Photosynthesis is the process whereby a green plant builds simple sugars using CO2, H2O and Sunlight. These simple sugars, or carbohydrates, are the building blocks for all plant parts. Aside from anchoring a plant to the ground, roots uptake moisture and nutrients. As roots die off, new roots are developed using carbohydrates. Going back to the opening paragraph, carbohydrate production (photosynthesis) lessens in the summer. Therefore, it becomes very important to protect the existing root mass.

Oxygen is very important to root-zone health. Aside from its chemical role in metabolic processes, oxygen is less dense than water so if a root zone is well aerated, it doesn't get as hot as a saturated root zone. Bent grass roots begin dying when soil temperatures eclipse 85 degrees Fahrenheit, so maintaining a well-aerated root zone is crucial. Also, as the grass canopy becomes more compacted due to rolling and mowing, gas exchange slows dramatically. Although CO2 is pivotal in carbohydrate production, an over abundance of CO2 in the root-zone can become toxic.

So, we know that oxygen is important to root health because: (1) it plays a role in plant metabolism; (2) it displaces water in the macro-pore space which keeps the soil from scalding the plant and (3) it displaces built-up CO2, which can be toxic to bent grass roots. We also know that golfers expect firm, fast greens no matter the season. To mitigate the combination of Mother Nature and golfer expectations, superintendents have various ways to vent the putting surfaces. Venting can occur through spiking, tining, air injection and water injection. For our purposes, we utilize mechanical spiking and tining.

At least twice per month beginning after Memorial Day, we needle tine our greens. We either use an 8 or 5 mm tine that is driven approximately 3" down on 1.5" x 1.5" centers. This process creates small holes in the surface of the green. This process is unobtrusive to golfers while limiting compaction, encouraging gas exchange, aiding in water infiltration and allowing the soil to dry down more uniformly.  It is impossible to have healthy, sustainable grass without a great root-zone. Needle tining greens is a great tool that helps us maintain adequate rooting throughout the heat of summer.

Oscillating Fans

One of the best tools that a grass grower possesses is oscillating fans situated near putting green surfaces.

Do you ever wonder why the healthiest greens are those perched on a hill or sitting near a lake?

The reason is air flow. When we get hot, we sweat. The perspiration released onto the surface of our skin helps to cool us. If we didn't sweat, we would die due to heat stress. Grass plants are no different. When grass plants get hot, they release water droplets through tiny openings in the leaves. (stomata) As wind passes by, the leaf surface is cooled and the plants internal temperature is regulated. However, plants obey osmotic principles above all else. For a plant cell to release water, there must be less water outside the cell than within. In the summertime, humidity builds over the putting green. If there is no wind due to the green's micro-environment, that humidity becomes a blanket of sorts. With all that moisture in the air, the plant has nowhere to release water droplets. If the plant cannot release water droplets, it begins to overheat and eventually die. Furthermore, plants that retain moisture in their leaves pull less moisture from the rootzone. Too much moisture in the rootzone creates anaerobic conditions that lead to root death and potentially wet wilt. The moral of the story is that plants need to sweat. (evapo-transpire) On sites where natural air flow is limited, oscillating fans are unbelievably useful. By providing the environment with consistent breezes, humidity cannot build into a thermal blanket. Without excess humidity, the air surrounding the plant tissue has less water than within the plant tissue and sweating can commence. This allows the plant to stay cooler and not fall victim to heat stress. Not to mention the plant pulls more water from the rootzone thus leaving more pore space available for oxygen. All in all, oscillating fans are a very good tool for today's superintendent.

Fertilizing for Endurance Not Growth

The middle of May marks a shift in our approach towards plant fertility. In the earlier part of the growing season, we are trying to get the plant to grow and move by enhancing photosynthetic potential. We accomplish this by applying Nitrogen, Magnesium, Iron and Phosphorous. Nitrogen, in particular, is a major component in chlorophyll production and the establishment of proteins. By giving the plant more Nitrogen (in combination with Iron, Magnesium, Sulfur, etc.) the plant can produce more chlorophyll and thus build more carbohydrates through photosynthesis. As the weather gets warmer, the plants photosynthetic potential lessens as its respiration rates increase. Effectively, the plant begins a net-negative carbohydrate production cycle. Because Nitrogen makes a plant grow and growing expends carbohydrates, we want the plant to "settle down" during the hot, humid stretches of summer. We "settle" the plant down by restricting N fertility while continuing our PGR programs. Although Nitrogen fertility is reduced in preparation for the summer months, plant fertility does continue. However, the type of fertility is what changes. In the latter spring and throughout the summer, our fertility plan centers on Calcium, Potassium and Micros. Calcium is a strength mineral that plays a major role in cell strength. If cell walls are strong, grass plants can endure more stress. Potassium helps regulate water movement and helps the plant maintain turgor pressure. Turgor pressure allows the plant to stand more vertical and thus absorb traffic better. Micros are essential nutrients that you may liken to vitamins. Put all of these minerals together and you have a fertility program designed to endure. Once we start seeing the cooler temperatures of the fall season, growth and recovery become the objective and Nitrogen is re-introduced to the program.

Grooming Turf

Grooming turf is an especially important maintenance practice. Over time, bent grass leaves will tend to "lay over" and grow in a more horizontal habit. In this prostrate position, it is easier for the mower to pass over the leaf tissue without actually cutting the length of the turf. As this trend continues, the plant is forced to supply more energy to these "leggy" leaves and thus these leaves get longer, fatter and lay over even more. Over time, plant density and ball roll are adversely affected. Grooming is the process wherein mechanical blades spinning downward pick-up the laid over leaves so that the bed knife can clip the plant closer to the crown. The crown of the plant is the control center and from the crown comes the distribution of energy. If the leaves are cropped tighter there is less leaf tissue demanding energy and the crown of the plant can re-allocate its resources to new nodes and tillers. This process creates a denser, tighter turf that is healthier and more suitable for consistent ball roll.