- Healthy lawns can prevent phosphorus from entering lakes and streams, where it causes problematic algal blooms. Phosphorus is an important element for plant growth. It binds tightly to soil, and it can be lost when hard rain detaches soil particles and carries them away with flowing water (otherwise known as runoff ). The dense ground cover of a healthy lawn protects soil particles from detachment and increases the lawn’s ability to absorb water. Research by the late CALS soil scientist Wayne Kussow BS’61, MS’63, PhD’67 and others has shown that fertilized lawns (with or without phosphorus fertilizer) can decrease the amount of phosphorus that’s lost. This is because the nitrogen in lawn fertilizers increases the density of the grass and keeps the phosphorus in the soil.
- Phosphorus fertilizer can’t be applied to lawns in Wisconsin without a soil test showing the need. Many Wisconsin lawns contain enough phosphorus for healthy plant growth for decades. The nitrogen in lawn fertilizer is quickly assimilated into the lawn leaves, and studies have consistently reported low levels of nitrogen loss — often 10 times lower than nitrogen losses from corn, despite similar levels of fertilization.
- Like native prairies and other perennial grasslands, lawns can fight climate change by taking carbon dioxide from the air and locking it in the soil in the form of organic matter. Many studies have documented increases in carbon-rich soil organic matter when agricultural areas are converted to lawns. However, maintaining a lawn by mowing, irrigating, and fertilizing emits carbon dioxide. To maximize soil carbon storage, lawn owners should consider using robotic or electric mowers, which use much less energy than traditional mowers. They should also avoid or reduce irrigation because it consumes electricity for pumping, and they could consider incorporating clovers, which convert atmospheric nitrogen to plant-available nitrogen.
- How you mow your lawn matters. The “one-third rule” states that no more than one-third of the leaf blade should be removed during each mowing. For example, if you plan to mow your grass to a height of 3 inches, mow it before it reaches 4.5 inches (1.5 is exactly one-third of 4.5). Mowing more than one-third of the blade stresses the grass, thins the canopy, and reduces the function of the lawn. Also, in general, the shorter you mow your grass, the faster it grows. Lawn owners who don’t enjoy mowing should raise their mower decks; then they can mow less frequently and still follow the one-third rule. Another benefit to mowing high is that, according to CALS research conducted at the O.J. Noer Turfgrass Research and Education Facility, it allows fewer weeds to invade.
- Speaking of weeds, lawn owners may want to reconsider their stance on these “undesirable” flora. Plants like dandelion are traditionally considered weeds in lawns, but they can be important sources of food for pollinators in urban areas in early spring. A movement called “No Mow May” began in Wisconsin and has gained traction nationally. The purpose of not mowing in May is to allow pollinators access to dandelion and other early blooming flowers in spring lawns. However, not mowing for the entire month of May can cause lawn maintenance and plant health problems in June. To achieve No Mow May goals while preventing June challenges, lawn owners should consider mowing as high as possible in May and throughout the growing season. Flowering lawn plants such as clover, dandelion, and creeping Charlie produce most of their blooms below 4 inches. When you mow high, you can have your cake and eat it, too.
Doug Soldat is a professor and extension specialist in the Department of Soil Science. He received his bachelor’s and master’s degrees in soil science from CALS and a Ph.D. in horticulture from Cornell University.
This article was posted in Basic Science, Changing Climate, Front List, Healthy Ecosystems, Spring 2023 and tagged carbon, Doug Soldat, Extension, lawn care, No Mow May, O.J. Noer Turfgrass Research and Education Facility, phosphorus, pollinators, Soil science, sustainability, UW Division of Extension, Wayne Kussow.