Different grasses are intended for different uses based on their growth habits, nutritional value, and tolerance to management practices. Turf grasses are bred primarily for aesthetic and recreational purposes. They are designed to form dense, uniform, and visually appealing ground cover that can withstand frequent mowing and foot traffic. Commonly used in lawns, sports fields, and golf courses, turf grasses are maintained at a low height and are selected for their fine texture, color, and resilience.
In contrast, forage grasses are developed to provide nutrition for grazing livestock and are selected for their ability to produce high biomass, regrow quickly after grazing, and thrive under rotational management systems. The goal with forage grasses is not appearance, but optimal growth stages that provide the highest nutritional content for animals. Because of this, maintaining the correct grazing height is critical to keep the plant in a vegetative state, which is when it is most digestible and nutrient-rich. For example, most warm-season pasture grasses, including bermudagrass, should not be grazed or mowed below 3 inches. Grazing too short can weaken the plant, reduce regrowth, and lower forage quality.
Does anyone remember this equation? 6CO2 + 6H2O + sunlight —> C6H12O6 + 6O2. This is the chemical equation for photosynthesis. Plants are amazing because they can make their energy using water, carbon dioxide, and sunlight, absorbed with their own personal solar panels, their leaves.
What’s below the soil’s surface is also very important. The plant’s roots are responsible for absorbing water and nutrients the plant needs to grow. The roots are also used to store carbohydrates for winter survival and regrowth after defoliation. Different plants have different root storage characteristics. Frequent defoliation (leaf removal) through grazing or mowing does not allow root reserves to replenish and with continuous withdrawals from the carhohydrate savings account to produce new leaves and no deposits, the plan will eventually run out of energy. Overgrazing and continual mowing below ideal grass height not only decreases the amount of plant material you see on top, but it also affects the root depth. What you see on top of the soil is about equal to what is below the soil. Shallower roots decrease the plant’s competitiveness for water which can allow undesirable plants to start to take over. Going into winter with shallow roots and less than 3 inches of stubble can lead to winter kill.
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Mowing is an effective way to help keep your pasture grasses in a vegetative state; however, it is important not to mow the grass below 3 to 4 inches. Knowing the height of the blades and mower deck on the equipment you are using to mow your pastures is very important. Most riding mowers like yard tractors and zero turn mowers, which are commonly used on smaller farms, have a scale of numbers indicating the height of the blades; however, these numbers do not indicate the actual cutting height. Most ride on mowers have a maximum cutting height of 4 inches.
Height does matter in some situations, especially when it comes to good pasture management. If you have any questions about pasture management, including taking soil samples, grazing management, and weed control, reach out to Liz Joseph at the N.C. Cooperative Extension, Moore County Center at 910-947-3188 or liz_joseph@ncsu.edu.
