Effect of fertilizer nitrogen rate and time of application on growth and performance of six herbaceous perennials and soil solution nitrogen concentration in a simulated landscape

by 1966- Proctor, Cynthia Lambert

PROCTOR, CYNTHIA LAMBERT. Effect of fertilizer nitrogen rate and time of application on growth and performance of six herbaceous perennials and soil solution nitrogen concentration in a simulated landscape. (Under the direction of Stuart L. Warren) Herbaceous perennials are planted worldwide in public gardens, and commercial and home landscapes. Little research based information exists on response of herbaceous perennials to fertilizer nitrogen (FN) rate and timing and the potential for loss of applied N via leaching. Therefore, we constructed simulated landscapes and installed canna lily (Canna L. 'President'), coreopsis (Coreopsis verticillata L. 'Moonbeam' ), purple coneflower (Echinacea purpurea L. 'Magnus'), iris (Iris siberica L. 'Caesar’s Brother'), switchgrass (Panicum virgatum L. 'Shenandoah'), sedum (Sedum L. 'Herbstfreude'), and sage (Salvia x sylvestris L. 'East Friesland') to determine how FN rate and timing affected growth and performance of herbaceous perennials and potential N leaching. Porous ceramic cup lysimeters were installed in situ in each landscape plot 38 cm below the soil surface to examine the effects of FN rate and timing on soil solution N concentrations. The experiment was a 4 x 4 factorial in a randomized complete block design with four replications. Four rates of FN: 0, 7, 14, and 28 g•m-2 N were divided equally into two applications and applied at the following times: 1) winter (Jan. 15 and Feb.15), 2) spring (Apr. 15 and May 15), 3) summer (June 15 and July 15), or 4) fall (Sept. 15 and Oct.15) beginning 2001. Soil solution samples were collected approximately every 2 weeks from Jan. 30, 2002 to Nov. 3, 2003 and analyzed to determine soil N (NO3- and NH4+) concentrations. Data collected in 2002 and 2003 for each species included the following number of flowers, plant visual evaluations, growth index (GI), and top dry weight. In 2003, mineral nutrient concentration was determined for each species. Plant response to treatments varied in 2002 and 2003. Our results indicated that despite statistical significance differences, many differences were small and FN treatments had little impact on the growth and ornamental qualities of these species. However, applying no N may not advisable, as some perennials species did benefit from an FN application during a specific time. Soil N concentrations remained above 10 mg•L-1 for 110 days, 62 days, 52 days, and 192 days when applied during January/February, April/May, June/July, 2002 and September/October in 2001 respectively. In 2003, soil N concentrations from FN rates of 7 g•m-2 N (1.5 lbs•1000 ft-2) and 14 g•m-2 N (3.0 lbs•1000 ft-2) applied in January/February, June/July, April/May and September/October remained below 10 mg•L-1 until the end of the study (Oct. 14, 2003). Nitrogen concentrations increased to 19 mg•L-1, 38 mg•L-1, and 21 mg•L-1, after 28 g•m-2 N (6.0 lbs•1000 ft-2) was applied in January/February, April/May, and June/July, respectively. To cover the needs of a wide variety of perennial species that usually exists in one landscape as well as minimize N concentrations in the soil solutions, we recommend a low to moderate rate of FN (5 g•m-2 to 15 g•m-2 ) be applied in split applications in spring and early fall. Effect of fertilizer nitrogen rate and time of application on growth and performance of six herbaceous perennials and soil solution nitrogen concentration in a simulated landscape by