By Madeline Leslie, Graduate Research Assistant
Climate change is a serious environmental issue that will continue to cause widespread concern around the globe. As the amount of carbon dioxide, nitrous oxide, and methane increase in our atmosphere, the ongoing effects of higher temperatures will become more apparent. We have already seen certain trends occurring that scientists have attributed to climate change, such as more frequent droughts, higher sea levels, melting glaciers, and shifting plant and animal ranges (IPCC, 2007). Society can help to help mitigate the effects of climate change in two ways. One is the reduction of greenhouse gas emissions, and the other is the sequestration of carbon dioxide within natural or artificial reserves.
Turfgrass is often seen as a high input landscape feature and as such has acquired a bad reputation because of the negative consequences associated with high input management. Fertilizer and pesticides applied in excess can run off turf areas and contaminate local waterways. Additionally, lawn mowers, aerators, and other turf maintenance equipment release greenhouse gasses into the atmosphere. Despite these negative impacts, turfgrass actually has the potential to offset emissions by sequestering carbon dioxide. Through the process of photosynthesis, all plants remove carbon dioxide from the air and utilize it to form new growth, including root mass. As turfgrass roots die, they decompose into soil organic matter, fixing carbon in the soil. In this way, turf areas can sometimes be carbon sink for greenhouse gases rather than a source.
Recently, some significant research has been conducted that has shown encouraging results regarding the ability of turfgrass to sequester carbon. One such study used a model to examine the potential for carbon sequestration on home lawns, and found that lawns are able to sequester anywhere from 25.4 to 204.3 g C/m2/year (Zirkle et al., 2011). Though this is only a small fraction of the amount emitted by the United States each year (EPA, 2013), if all or most turf areas were able to sequester this amount, a significant difference could be made in the net carbon emission of the United States. Kong, et. al. (2014) found that athletic fields, parks, and university campus lawns also had the ability to sequester more carbon than they emitted. However, this study also pointed out that there are limitations to how much carbon soil can hold, and as such turf areas can only sequester carbon for a certain amount of time. Finally, a study conducted on home lawns around the U.S. also found that these areas could sequester more carbon than they released, but on average became net carbon sources after 184 years, as the soil ceased to be able to hold additional carbon, but maintenance activities continued (Selhorst and Lal, 2012).
These studies show that turfgrass areas do indeed have the potential to sequester more carbon than they emit, therefore at least not contributing to the problem of global warming. However, after a certain amount of time turfgrass becomes a net source of greenhouse gasses when the soil reaches its carbon storage capacity. The length of this time period depends on many factors, such as soil type and climate, but especially on maintenance practices. More research is needed on what environmental conditions result in the maximum amount of soil carbon storage, but individuals can take immediate action on their own by choosing to plant a low-input turfgrass species, which will reduce emissions from maintenance. This will increase the likelihood that your turf area will be a net sink for carbon for a longer period of time; while this by itself will not solve the problem of global warming, it at least can help reduce it.
EIA. 2013. What are greenhouse gases and how much are emitted by the United States?. EIA: Energy in Brief.
IPCC. 2007. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, 2007. IPCC.
Parry, M.L., O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson (eds) Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
Selhorst, A., and R. Lal. 2012. Net Carbon Sequestration Potential and Emissions in Home Lawn Turfgrasses of the United States. Environ. Manage. 51(1): 198–208.
Zirkle, G., R. Lal, and B. Augustin. 2011. Modeling carbon sequestration in home lawns. HortScience 46(5): 808–814.
The month of June was a wet one. Many homeowners, grounds managers, and golf course superintendents are finally starting to see some of the flood waters recede, although standing water is still covering many of our landscapes. The University of Minnesota’s Climatology Working Group is calling June of 2014 the wettest month on record. In the Twin Cities we saw 11.36 inches of rain for the month, almost 7 inches above average and falling just short of the 11.67 inch record set in 1874 (www.climate.umn.edu).
We are starting to see a wide range of damage to lawns and turfgrass throughout the state. In situations where standing water was present for greater than 7-10 days, the turf is almost certainly dead and will need to be repaired. Turfgrass covered for less time has a greater chance of recovery, but every situation is different. Unfortunately, there is not good information regarding how long turfgrass can survive under standing water because there are so many potential mechanisms of damage. These mechanisms can be separated into 2 groups: primary damage from waterlogging and secondary damage after the water has gone.
Primary damage includes such factors as water temperature and water depth. Water temperature will probably be the most important factor determining survival, with turfgrass death occurring in only a few days when water temperatures are 80 degrees F and higher (note: we did not see water temperatures this high during recent floods, unless it was very shallow and stagnant). When water temperatures are lower the turf can still die, with lack of oxygen being the primary culprit. If the turf is completely submerged, this will be a worse case than if some of the leaves and crowns are exposed.
Secondary damage might be associated with sediment buildup, fungal diseases, moss and algae, and weed infestation. While we have very little control over the primary mechanisms causing damage, now is the time to start thinking about how to reduce damage that could be caused by the secondary mechanisms. The primary disease you could expect to occur after flooding is pythium blight. Look for circular or irregular patterns of dead turf inside of healthy turf areas. For more information on pythium blight, follow this link to a fact sheet from Purdue University Extension: Pythium Blight. Remember that plant disease samples can be submitted to the University of Minnesota Plant Disease Clinic for correct identification and control recommendations. If you have confirmed that you lawn is infected with pythium or other diseases, I recommend contacting a lawn care contractor to carry out the control measures.
To this point I’ve been recommending that homeowners be patient and assess the damage as it presents itself. Turf that appears to be dead following the receding of flood waters should be monitored for several days; if no green tissue appears within 7-10 days, you can assume it is dead and should start forming a renovation plan. In many cases, you might be surprised with the amount of turf that recovers when the conditions are right. In situations where sediment or debris buildup has occurred, you will want to act fast to remove it. The previous Turfgrass Extension Educator, Bob Mugaas, wrote a great article addressing repair of areas where sediment has built up in the 2010 edition of the Yard and Garden News. That article can be found here: Repairing Flooded Lawns
Timing of repair can be difficult. The cool-season grasses that we grow in Minnesota do not establish well in the middle of the summer due to the high heat and diseases that may occur. If at all possible, I recommend waiting to seed until temperatures cool in the early fall around mid- to late-August. Fall seeded lawns will have a much better chance of a successful establishment. With that being said, recovery in the short term could be promoted by aerating your soil once it is dry and/or applying light rates of nitrogen based fertilizer.
Choice of turfgrass seed can be very important. If flooding is a common occurrence on your lawn, I would recommend Kentucky bluegrass over perennial ryegrass or fine fescues. The University of Minnesota Extension has numerous resources to help you in repair process. Please follow these links for more information:
Finally, feel free to reach out if we can be of help. You can contact me directly at: firstname.lastname@example.org or 763-767-3518
Dear Twin Cities Resident,
Graduate student Madeline Leslie is offering a lawn care survey (with prizes) to collect data for a Master’s degree thesis project. If you have time please complete the survey below to provide information on your lawn care practices.
The grass-growing season is in full swing, and for some of you this means repairing turfgrass areas that were impacted by winter injury. By now, it should be apparent which areas of your lawn were damaged (but not killed) from winter stresses and which areas will not recover from winter injury. Plants that are slowly recovering, suffered damage only to the leaves and are able to produce new leaves during the spring. Practices such as removing dead leaf tissue and fertilizing will help expedite the recovery of these areas. In contrast, plants that are dead suffered damage to the crown tissue (survival organ of turfgrasses) and will need to be renovated and repaired. The goal of this post is to provide you with information on the different types of winter stresses that effect turfgrass plants and the cultural practices that can be used to minimize winter injury. In addition, a step-by-step outline of the recovery/renovation process is provided.
Repairing dead turfgrass on a yearly basis can be both time and labor intensive and is an unnecessary added expense. Therefore, one of the first steps to minimizing winter injury is to identify the primary cause of damage. In Minnesota, damage detected in the spring may be attributed to several different stresses that the turfgrass is exposed to during winter months. Specifically, there are five main stresses associated with low temperatures and each has the potential to cause damage and/or death of your lawn. Crown hydration is associated with elevated temperatures (above freezing) and results in an increase in water content of the turfgrass plant. This can be lethal if hydrated tissues are then re-exposed to freezing temperatures causing ice crystals to rupture cells in the leaves and crown. Desiccation causes severe dehydration of plant tissues due to lack of snow cover or inadequate moisture and is generally a problem on elevated areas exposed to wind. Prolonged ice cover can also be damaging to lawns by creating an impermeable layer above the turf resulting in a depletion of oxygen and a build up of gasses that are toxic to lawn grasses. Additionally, grasses can die simply from exposure to low temperatures; however, damage associated with temperatures at or below freezing is minor during winters with adequate snow cover. Finally, snow molds are a common occurrence in Minnesota and winter damage associated with these diseases occur every year. For more information on snow molds, visit this article by Michelle Grabowski: http://blog.lib.umn.edu/efans/ygnews/2013/05/snow-molds-blight-minnesota-la.html. Altogether, these stresses can occur as a complex to cause damage that potentially could be lethal to the turfgrass in your lawn.
Along with the five mechanisms causing winter injury to lawns, there are also many other abiotic stresses that occur throughout the spring period. Salt loading from the use of de-icing salts commonly causes damage to turf along roadsides, sidewalks, and driveways. Primarily, these salts cause severe desiccation of leaf and crown tissue and ultimately result in death of the turfgrass plant. By the time the salts are leached through the soil profile with spring rains, most of the damage has been done. In addition to deicing salts, dog urine spots can kill grass from the high salt content and can cause excessive growth due to nitrogen in the urine. Mechanical damage caused by snowplows, mowing too early, and power raking early in the season can also result in areas of turfgrass that need to be repaired in the spring.
Preventing/minimizing winter injury is a yearlong process and involves knowing your lawn and carefully considering the maintenance practices utilized to maintain the turfgrass. For example, in areas that frequently accumulate standing water, core aeration will help with water infiltration as snow melts in response to warming temperatures. Overall, this will reduce the potential for crown hydration and ice crystal formation along with helping to prevent the establishment of an impermeable ice layer. An additional consideration is fertility, specifically associated with the application of nitrogen. Snow molds are more common on lush, succulent turf, and a heavy application of nitrogen in the fall could promote damage caused by snow molds. In addition, succulent turf is more prone to injury attributed to exposure to temperatures at or below freezing. Keep in mind that as summer transitions into fall keep the cultural practices implemented have a direct impact on the survival of turfgrass plants throughout the winter and into spring.
Steps for Recovery
Providing the right conditions for your lawn to thrive is the most important component of a good recovery program. While it’s up [Read more...]