Influence of Nitrogen Source and Application Timing on Large Patch of Zoysiagrass

• Published in: Crop, forage & turfgrass management forage & turfgrass management, 2016-12, Vol.2 (1), p.1-9
• Main Authors: Miller, G. L., Earlywine, D. T., Braun, R., Fry, J. D., Kennelly, M. M.
• Format: Article
• Language: English
• ISSN: 2374-3832; 2374-3832
• DOI: 10.2134/cftm2015.0189

Large patch of zoysiagrass (Zoysia spp.), caused by Rhizoctonia solani AG2‐2 LP, is a troublesome disease on golf course fairways in the upper transition zone of the United States. Turfgrass managers incur significant fungicide costs to control the disease over large acreages, and integrating cultural practices into an overall scheme of disease management may result in reduced inputs. Our objective was to assess the impact of applying different nitrogen sources at defined soil temperature thresholds during the fall and spring infection periods on large patch severity in field experiments conducted in Kansas and Missouri. From 2013 to 2015, ammonium sulfate [(NH4)2SO4], calcium nitrate [Ca(NO3)2], and urea were applied at 0.75 lb nitrogen (N)/1000 ft2 when 5‐day 2‐inch soil temperatures reached 60 or 70°F in the spring or declined to 70°F in the fall. Summer applications of urea at 0.5 lb N/1000 ft2 were utilized as a standard for comparison, with all treatments receiving a total of 1.5 lb N/1000 ft2 per year. In spring 2014, when large patch severity was greatest, percent green cover was higher in ammonium sulfate treatments compared with urea and the standard summer program in Missouri, and higher in ammonium sulfate–treated plots compared with calcium nitrate– and urea‐treated plots in Kansas. Although the effect was not consistent among sites, spring nitrogen applications made during the large patch infection period did not result in higher large patch severity than the standard summer fertilization schedule.