The Grass is Always Greener… when you use biosolids.
Spring is here and the grass has started greening up. This month’s library is devoted to growing grass using Class A biosolids products. The last time the library focused on this topic was June 2009 and back then most of the articles focused on composted biosolids. This time around, all but one focus on Class A biosolids. Biosolids and grass are a match made in turf heaven. The first article presents results from a long-term study funded in part by NBMA. Cogger et al. applied two types of biosolids applied at several rates in comparison to synthetic N every year for 10 years. For the next 9 years he sat back and watched the grass grow. During the active application period, the higher rates of biosolids out-yielded the synthetic fertilizer. The real story is what happened after applications stopped. All of the biosolids plots maintained higher yields and higher N availability for the next 9 years. Soil carbon and extractable P also increased in the biosolids amended soils. Phosphorus perks your interest there? Recently the use of pelletized biosolids for turf has been questioned in WA State because of the potential for P runoff. If this is your interest, go directly to the 3rd article in the library. Scientists from Australia compared runoff P from surface applied pelletized biosolids and poultry manure used on a turf farm. They found that the P in biosolids was much less likely to move than the P in chicken manure. You can continue to the 4th article that looked at runoff from composted biosolids used for establishing turf. Here authors found reduced runoff potential if the composted biosolids are incorporated into the soil before turf is placed on top rather than putting turf grown in biosolids compost on top of soil. This effect diminished over time (6 months) and was much more pronounced for one of the composts than the other. If N is your focus, you’ll want to take a look at articles #2 and #5. In the second article, the biosolids group from Chicago studied microbial biomass in general and the microbes that oxidize ammonia in particular for putting greens amended with different types of fertilizers including the Class A dry biosolids from Chicago. The microbes that oxidize ammonia are important because they transform it to nitrate, the form of N that plants generally prefer. Here the authors found that the populations of ammonia oxidizing bacteria in the biosolids amended greens were much greater than in all other treatments. This lead to greater nitrogen availability and greener grass in the biosolids amended treatments. The last study measured plant available N (PAN) in biosolids amended turf for two types of biosolids: a dewatered material and a pelletized material. The default mineralization rate for biosolids N in Australia is 25%. This study found that 50% was a more reasonable number for the first year following application. Remember that grass grows all year in Australia so that these results should be tailored to reflect growing conditions where you mow.
Dr. Sally Brown