By Sally Brown, University of Washington
Abstracts of these resources are available in the searchable Information Portal offered to Northwest Biosolids members.
Mapping and modeling the biogeochemical cycling of turf grasses in the United States
Urban grassland management implications for soil C and N dynamics: A microbial perspective
Compost Practices for Improving Soil Properties and Turfgrass Establishment and Quality on a Disturbed Urban Soil
Biosolids amendments improve an anthropogenically disturbed urban turfgrass system
Composted biosolids for golf course turfgrass management: Impacts on the T soil microbiome and nutrient cycling
A little levity for the last library of 2020. The way 2020 has gone, we can all use a little levity. Let’s skip the contaminants and focus on one of those unheralded end uses for biosolids and composts; our front and back yards. Here I am specifically focused on turf grass but you can easily extrapolate to include more exotic grasses and even hydrangeas.
Important links to this library include a feature on King 5 News Seattle featuring your favorite Biobull library author "Is Natural Grass or Artificial Turf Better For Your Backyard?"
And the Drawdown series that I’ve done for Biocycle, "Can Compost Draw Down Carbon?" with a chapter on turf slated for December.
Lawns have been much maligned as sucking up resources like food (nitrogen and phosphorus) and water. Excess use of both of those resources has also been associated with degradation of urban lakes and streams. But lawns can have an environmental upside, one that biosolids and compost make better. That is the focus of this library.
The first article puts that square of green in front of your house into perspective. There are lots of houses all across the country with that same square of green. The authors here have estimated the total area in the US currently in lawns or ‘irrigated grasslands’. It is enough to qualify this as the single largest irrigated crop in the country, covering acreage equivalent to the State of Washington. In other words, three times as much land as is used to grow irrigated corn. The authors of this article talk about the benefits of these lawns. The biggest one is soil carbon sequestration. High maintenance and plenty of food lead to plenty of growth. That growth means that lawns are carbon sinks for the first 60 or so years of their existence. The authors note that the food and water detract from the benefits.
From there the 2nd article is a review of the microbial community and ecosystem services provided by those lawns. They looked at a range of studies and found that in general, the microbes that live under the grass are used to living large. Availablility of food and water has made for a microbiome used to using the nutrients efficiently and cycling them efficiently. Ecosystem services associated with these grasslands include soil formation, nutrient cycling and soil water filtration and storage.
So now the state is set- lawns are not necessarily evil. They are in many ways a good deal. They are an even better deal if you keep them green with biosolids and composts instead of fertilizers. I’ve talked about biosolids for turf before. One article in the August 2019 library and then again in April of 2013. This library features 3 new (relatively) articles on the topic, one in part funded with NW Biosolids research dollars. Articles 3 and 4 in the library come from Greg Evanylo’s group at Virginia Tech. Article #3 tests a pulp sludge based compost as a fertilizer for newly established turf on urban soils. Two rates ; 2.5 and 5 cm depth, incorporated or surface applied are compared with fertilizer alone, fertilizer + straw, and a fertilizer + 0.6 cm compost blanket. The compost worked the best, better at the higher rate. Greener grass, reduced soil bulk density, and higher yields were the benefits. The compost amended soils got better with time. Paper #4 is a follow up to the Evanylo paper from last August. Here different types of biosolids including a Class A material, that material mixed with sand and sawdust (Think Bloom not Tagro) and composted biosolids. All worked great. Even though high rates of P were added, because of the Fe in the biosolids it generally was not available in excess. Yield in the fertilizer treatment was highest initially and then tanked- recovering a bit towards the end of the trial. Biosolids, especially the compost in my opinion, had more consistent high yields. The blends and regular cake did well too. All of the organics reduced bulk density. All stored a lot of carbon, again compost to me did the best.
Paper #5 is out of WSU and reports on biosolids compost applications to golf courses at Joint Base Lewis McChord, just south of Tacoma. Again- plenty of green grass. And again- biosolids did not alter the microbes living in the soil.
The take home for all of this is that our irrigated grasslands aka lawns, can be great carbon sinks that provide other important ecosystem services in urban areas. By using organics like compost and biosolids you make these green lawns both visibly green and environmentally green. And you get a local customer base.
Stay safe and hope you enjoyed the holiday season!