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.