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.

Can Frequent Measurement of Normalized Difference Vegetative Index and Soil Nitrate Guide Nitrogen Fertilization of Kentucky Bluegrass Sod?

“…The most common spectral reflectance measurement for turfgrass is NDVI. Measurements of NDVI have been used to objectively assess turfgrass response in relation to N rates, soil N concentrations, or tissue N concentrations (Trenholm et al, 2001; Bell et al, 2002, 2004; Fitz‐Rodríguez and Choi, 2002; Stiegler et al, 2005; Trenholm and Unruh, 2005; Kruse et al, 2006; Baghzouz et al, 2007; Xiong et al, 2007; Barry et al, 2009; Johnsen et al, 2009; Flowers et al, 2010; Li et al, 2011; Zhu et al, 2012; Agati et al, 2013; Geng et al, 2014a, 2014b).…”

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

“…Dumort. ], 33–51 g kg −1 for perennial ryegrass, and 25–51 g kg −1 for Kentucky bluegrass (Mills & Jones, 1996), 27–35 g kg −1 for various species (Turner & Hummel, 1992), 30.4 to ≥34.7 g kg −1 for Kentucky bluegrass (Badra et al., 2006), 30–34 g N kg −1 for mixed species and separately for Kentucky bluegrass (Mangiafico & Guillard, 2007), and 32–46 g kg −1 and 28–42 g kg −1 for Kentucky bluegrass and tall fescue, respectively (Geng 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 >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 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 (Table 5).…”

Reference Ranges: A Novel Interpretation of Turfgrass Nutrient Values

“…A critical percentage exists between luxury consumption and poverty adjustment, and this approach has been used in turfgrass systems. Geng et al (2014) investigated Macy's concept using cool‐season turfgrasses and reported N sufficiency ranges were between 32 and 46 g kg ‐1 for Kentucky bluegrass ( Poa pratensis L.), whereas tall fescue ( Festuca arundinacea Schreb.) was slightly lower, with a range of 28 to 42 g kg ‐1 .…”

“…was slightly lower, with a range of 28 to 42 g kg ‐1 . Furthermore, Geng et al (2014) determined luxury consumption of N to be 46 and 42 g kg ‐1 in Kentucky bluegrass and tall fescue, respectively.…”