Ammonia Volatilization and Urease Activity in Turf
Torello, William Anthony
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https://hdl.handle.net/2142/71770
Description
Title
Ammonia Volatilization and Urease Activity in Turf
Author(s)
Torello, William Anthony
Issue Date
1981
Department of Study
Horticulture
Discipline
Horticulture
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Plant Physiology
Abstract
Experiments were conducted with recently developed turf microecosystems to determine the extent and mechanisms of NH(,3) volatilization from turf whose underlying soil had an acidic pH. Eight different nitrogen fertilizers were evaluated for NH(,3)-N losses after application to turf. The rate and mode of urea application as well as the effects of thatch were also assessed for their effects on NH(,3) volatilization.
Applications to turf of ammonium nitrate (NH(,4)NO(,3)), urea-form (UF), isobutylidene diurea (IBDU), and various sulfur-coated urea (SCU) fertilizers resulted in less than 1% N losses through NH(,3) volatilization. Prilled urea applications averaged 1.5% NH(,3)-N losses while spray-applied urea solutions at the same N rate (0.49 kg N/are) averaged 4.6% NH(,3)-N losses. The application of liquid ureaform fertilizers (FLUF and Formolene) yielded results similar to spray-applied urea solutions with NH(,3)-N losses averaging 3.9% of the total N applied. Ammonia-N losses increased 8-fold when urea application rates were increased from 0.49 to 2.93 kg N/are.
From these results, an "above soil" mechanism for NH(,3) volatilization was proposed assuming that there was extensive urease activity within the thatch and upon turfgrass plants. Therefore, experiments were conducted to compare the extent of urease activity associated with thatch and turfgrass to soil urease activity.
Thatch and turfgrass urease activity was found to be 20 to 30 times greater than soil urease activity. Previous experimentation had shown thatch urease activity to be greater in the upper portions of the thatch profile and that thatch urease activity was affected by seasonal temperature changes. Although thatch urease activity was variable between sampling sites, it remained extremely high compared to soil urease activity. Finally, experiments were conducted to assess the effects of urease on short-chained methylol and methylene ureas and to determine the origin of turfgrass tissue urease activity. Neither jack bean urease nor turfgrass urease had any affect upon methylene nor methylol ureas. Furthermore, it was suggested that these synthetic fertilizers had an inhibitory effect upon turfgrass urease activity.
Partial surface sterilization of turfgrass tissue followed by incubation in the presence of urea had resulted in a significant decline in urease activity. Therefore, it was concluded that the microbial population existing upon turfgrass tissue contributes significantly towards the total level of turfgrass urease activity.
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