Common centipedegrass is a popular turfgrass and has become widely grown in the southeastern United States from South Carolina to Florida and westward along the Gulf Coast states to Texas.  Centipedegrass is a low-maintenance turf used primarily for establishing home lawns.  It requires less fertilizer than most turfgrasses and has a light green color through most of the growing season.  Previous research indicates that centipedegrass requires ½ to 1 lb. of N per 1000 ft² per year. Centipedegrass has been reported to be particularly well adapted to sandy, acidic soils. However, some research indicates that when establishing from sprigs, growth is best during the first two years in soils with pH levels above 6.0. Observations of centipedegrass grown at Texas A&M University in College Station, TX, indicates that centipedegrass performs quite well in soils with pH levels above 8.0. Centipedegrass decline is the predominant problem in many lawns and may be induced by over fertilization and high mowing heights (over 2 inches).  Long term research experiments conducted at the University of Georgia at Griffin, GA in clayey soils, demonstrated that 2 lbs. of N/1000 ft² /year was the maximum N level that did not promote centipedegrass decline. The purpose of conducting this long-term centipedegrass fertilization trial is to determine the effects of soil pH, split vs. single applications of N at ½ lb. N/1000 ft² and 1 lb. N/1000 ft² and a single application of iron on the color, quality and density of centipedegrass in sandy soils.

    
     Soil pH levels of 5.5, 6.5 and 7.5 were obtained by liming according to soil analysis reports provided by the Clemson University Agricultural Services Laboratory. Dolomitic lime was applied to all treatments after core aerification to facilitate movement into the soil.  Hydrated lime was applied to achieve a soil pH of 7.5 (Figure 1).

     Nitrogen fertilization treatments were 0, ¼ lb. N/1000 ft² applied in May and July, ½ lb. N/1000 ft² applied in May, ½ lb. N/1000 ft² applied in May and July and 1 lb. N/1000 ft² applied in May. Ammonium nitrate was used as the N source for all treatments. In September, a chelated source of iron at 2.0 lbs of iron per acre will be applied to half of each plot. Plots were mown with a rotary mower and clippings returned.  Plots were rated for color, quality and density every two weeks from spring green up until dormancy.

     The experiment was conducted as a randomized split plot design with five treatments and three replicates. Data were averaged over five dates and analyzed by ANOVA and means separated at P=0.05 by the least significant difference test.

     There were no effects of soil pH on color (Table 1). Density was greater in plots with a soil pH of 6.5 and 7.5 compared to plots with a soil pH of 5.5. Quality was greatest in plots with a soil pH of 7.5 compared to plots with a soil pH of 5.5 and 6.5. These differences were statistically significant but not biologically significant since there was only a difference of 2 to 3 tenths of a quality point. In a study conducted at the University of Georgia in Griffin, GA in clayey soils, centipedegrass growth was best during the first 2 years after sprigging in soils with pH levels greater than or equal to 6.2. However, decline of centipedegrass occurred after this period when fertilized with 4 lbs. N/1000 ft²/year in soils with a pH level greater than or equal to 6.2 compared to no decline when grown in soil with pH 5.1.

     Color, density and quality was greater in test plots that received N compared to the control (Table 2 and Figure 2). Plots fertilized with a single application of 1 lb. N/1000 ft² in May had the highest color rating up until July 11, 8 weeks after application. There was no difference in color between ½ lb. N/1000 ft² applied in May and 1 lb. N/1000 ft² in May, 12 weeks after application (August 8). Plots that got an additional ½ lb. N/1000 ft² in July had the greatest color rating on August 8, which was 2 weeks after the July application. Turf quality and density did not increase with a July application of N and there was no difference in N treatments by August 8 except in color (Table 3). There were no apparent differences in color by September 5, 2002 (Figure 3). After one year of a four-year study, it appears that the application of ¼ lb. N/1000 ft² in May and July has the same effect on turf density and quality as treatments with higher N rates by August 8.