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AGRONOMIC AND ENVIRONMENTAL IMPACTS OF LAND APPLICATION OF BIOSOLIDS TO
BAHIAGRASS PASTURES IN FLORIDA
October, 2018
Dr. Maria Silveira,
UF/IFAS Range Cattle Research & Education Center, Ona
Biosolids have clear agronomic benefits, but concerns over nutrient
accumulation in soils and subsequent impacts on water quality can limit land
application in Florida. The project described in this article addresses
FCA Priorities # 9 “Land
Application of Biosolids on Pastures” and # 1 “Fertilization
(Alternative Fertilizer Sources). The main objective was to
establish a long-term, instrumented field trial designed to evaluate the
agronomic and environmental impacts of land application biosolids to
bahiagrass pastures.
Biosolids (Class AA and B materials) were surface applied to the
experimental area on April 2016, 2017, and 2018 and compared to nutrition
provided with mineral fertilizers. Biosolids were applied either alone or in
combination with biochar (a fine-grained carbon-rich residue produced
through the pyrolysis of wood biomass) to supply an estimated rate of 160 lb
plant available N/A/yr, which correspond to UF/IFAS high N option for
established bahiagrass. During the 2017 and 2018 (currently underway),
forage, water, and gas quality samples were collected and analyzed.
Results from 2017 indicated that addition of
fertilizer (either as commercial N and P fertilizer or biosolids) increased
annual bahiagrass herbage accumulation by an average of 68%; however,
no difference
between inorganic fertilizer vs
biosolids treatments
was observed. Although
inorganic fertilizer resulted in greater bahiagrass herbage accumulation in
the first harvest, at the end of the
growing season, greater bahiagrass herbage accumulation was associated with
treatments receiving biosolids. This response was due to the slow release
nature of nutrients present in biosolids. Similarly, no differences in
bahiagrass crude protein and digestibility were observed among fertilizer
and biosolids treatments. Results from this study indicated that biosolids
application can supplement or replace inorganic fertilizer in bahiagrass
pastures, with the added benefit of providing a more continuous supply of
nutrients throughout the growing season.
During the 2017 growing season, application of biosolids (either alone or in
combination with biochar) had no significant impact on water quality and
greenhouse gas emissions. However, when bahiagrass received commercial
inorganic fertilizer, large pulses of N and P were observed immediately
after fertilizer application. Similar responses were also observed for
nitrous oxide emissions. Greater nitrous oxide emissions were generally
associated with the treatments receiving commercial fertilizer, particularly
during the first few weeks following fertilization application. These
results indicated that N and P losses associated with treatments receiving
biosolids can be lower than commercial fertilizer. Results also indicated no
potential benefit of biochar in reducing N and P losses. Forage and
environmental data evaluations for the 2018 growing season are currently
underway.
ACKNOLEDGEMENTS
We thank H&H liquid disposal for their assistance obtaining and hauling the biosolids materials to the study site. We also want to extend our appreciation to the FCA for providing the funds to support this project.