Defining Sufficiency Levels of Nitrogen in Cool‐Season Turfgrass Lawns Using Macy's Concept

Abstract

Few correlation or calibration studies have been conducted to determine or validate sufficiency levels of N concentrations in the clippings of turfgrass for color and growth responses. In a series of field experiments conducted across six consecutive growing seasons (2007–2012) in Connecticut, clipping samples of Kentucky bluegrass (Poa pratensis L.) and tall fescue (Festuca arundinacea Schreb.) lawns were used to estimate yields and then analyzed for N concentrations. Chlorophyll and normalized difference vegetative index (NDVI) meters were used to quantify turf color before sampling. Macy's concept of three nutritional zones of plant tissue nutrient concentration was used to identify minimum and critical concentrations of N in the clippings that define sufficiency ranges for color and growth responses, in addition to luxury consumption. Averaged across all variables and seasons (spring, summer, and fall), the sufficiency ranges of N concentration in the clippings were estimated to be 32 to 46 g kg–1 for Kentucky bluegrass, and 28 to 42 g kg–1 for tall fescue. Differences in minimum and critical concentrations among seasons and between species were thought to be due to demand‐driven nutrient uptake. Luxury consumption of N was observed in both species. When used in context with local conditions, tissue analysis for N concentrations in cool‐season turfgrass clippings can provide an objective basis for guiding N fertilization.

Agronomic performance of white oats cultivated under fertigation with treated sewage effluent and definition of critical limits of Normalized Difference Vegetation Index

“…The chlorophyll content is influenced by the amount of N absorbed by plants. However, the excessive consumption of this nutrient does not interfere with the chlorophyll content (Geng et al 2014). Thus, from a determined N rate, NDVI values will not show significant increases.…”

Guiding fall fertilization of cool‐season turfgrass lawns with verdure tissue‐N tests

“…Dumort. ], 33 to 51 g kg -1 for perennial ryegrass, and 25 to 51 g kg -1 for Kentucky bluegrass (Mills & Jones, 1996), 27 to 35 g kg -1 for various species (Turner & Hummel, 1992), 30.4 to ≥ 34.7 g kg -1 for Kentucky bluegrass (Badra et al, 2006), 30 to 34 g N kg -1 for mixed species and separately for Kentucky bluegrass (Mangiafico & Guillard, 2007), and 32 to 46 g kg -1 and 28 to 42 g kg -1 for Kentucky bluegrass and tall fescue, respectively (Geng, Guillard, Mangiafico et al, 2014). These previous studies, however, report total N concentrations in the clippings and not the verdure.…”

“…The increase in verdure dry-tissue extractable NO 3 -N concentrations when total N concentrations are greater than 34 g kg -1 during the fall months ( Figure 3) also suggests luxury consumption of N. This increase can be attributed to storage of NO 3 beyond that needed for maintenance as turfgrass plants were preparing for winter dormancy. Averaged across years and seasons, Kentucky bluegrass and tall fescue lawns exhibited luxury consumption of N when clippings N concentrations exceeded 42 and 46 g kg -1 , respectively (Geng, Guillard, Mangiafico et al, 2014). As a percentage of the maximum or plateau values, the estimated verdure total N concentrations ranged from 60 to 70% for the 24.5, kg N ha -1 rate, 68 to 81% for the 49 kg N ha -1 rate, and 81 to 100% for the 98 kg N ha -1 rate (…”

“…Sufficiency or critical concentrations of total N in the clippings of various perennial coolseason turfgrasses range from 24 to 82 g kg -1 , depending upon species and management systems (Badra et al, 2006;Butler & Hodges, 1967;Geng, Guillard, Mangiafico, and Morris, 2014;Mangiafico & Guillard, 2007;Mills & Jones, 1996;Smith, Cornforth, & Henderson, 1985;Turner & Hummel, 1992). There are higher N concentrations in clippings than in the associated verdure (the aerial shoots and leaf blades remaining after mowing) (Kaufmann & Aldous, 1980;Picchioni & Quiroga-Garza, 1999).…”

Guiding fall fertilization of cool‐season turfgrass lawns with NDVI sufficiency index

“…A commonly used spectral measurement in turfgrass research to determine treatment differences is the normalized difference vegetative index (NDVI). There are numerous citations in the turfgrass literature reporting significant relationships between NDVI or other spectralreflectance signals with N fertilization (reviewed in Bell, Kruse, & Krum, 2013;Catureglia et al, 2015Catureglia et al, , 2016Caturegli et al, 2020;Geng, Guillard, Mangiafico, & Morris, 2014;Guillard, Fitzpatrick, & Burdett, 2016;Inguagiato & Guillard, 2016;Obear, Kreuser, Hubbard, DeBels, & Soldat, 2017). However, relationships between reflectance signals and the response of turfgrass to N fertilization have not been analyzed with the objective to create site-specific fertilizer recommendations.…”