Chemical Composition and Quality of Penncross Creeping Bentgrass as Affected by Ammonium, Nitrate, and Several Fungicides
1976
Mazur, A. R. | Hughes, T. D.
Several fungicides that are widely used on turfgrasses have been shown to inhibit mineralization of N in soils. The fact that most fertilizer materials commonly used on turfgrasses supply N as urea or NH₄⁺ promoted the present investigations. Nutrient-sand culture studies utilizing large volumes of nutrient solution with accurate control of pH and frequency and duration of wetting cycles were conducted in the greenhouse to determine the effect of NH₄⁺ and NO₃⁻ on growth and chemical composition of ‘Penncross’ creeping bentgrass (Agrostis palustris Huds.) Greater amounts of growth were observed for plants receiving one-half or all N as NO₃⁻. Plants receiving NO₃⁻ as a sole source of N generally contained lesser amounts of soluble carbohydrate and greater amounts of total N than those receiving all N as NH₄⁺. Seasonal fluctuations in growth, soluble carbohydrates, and total N were observed. Growth generally decreased during the period from April to May through October to November. Soluble carbohydrates and total N decreased during the period April to May through July to August; and increased during the period July to August through the October to November. Low soluble carbohydrate levels during July to August were attributed to respirational losses and tended to emphasize the importance of carbohydrates in N assimilation. Field studies on a Drummer silty clay loam (member of fine-silty, mixed, mesic family of Typic Haplaquolls) did not show any differential effect of NH₄⁺ and NO₃⁻ on turf quality or chemical composition of leaf tissue. The rapid conversion of NH₄⁺ to NO₃⁻ undoubtedly accounted for the lack of differences under field conditions as compared to those observed in solution cultures. Fungicides were shown to influence both soluble carbohydrate levels and turf quality ratings in the field.
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