Using the SPAD 502 Meter to Assess Chlorophyll and Nitrogen Content of Benjamin Fig and Cottonwood Leaves

Abstract

<jats:p>A Minolta SPAD-502 leaf chlorophyll meter was used for nondestructive data collection on the chlorophyll and nitrogen (N) status of benjamin fig (<jats:italic>Ficus benjamina</jats:italic>) and cottonwood (<jats:italic>Populus deltoides</jats:italic>) to quantitatively evaluate foliage quality. The goal was to provide a specific calibration for interpreting SPAD data within a media study for each species. Triplicate SPAD readings were collected from each of six leaves, sampled from forty plants per species, then processed for foliar analysis. Leaf tissue disks were also collected directly over SPAD testing sites for chlorophyll concentration measurement. Significant linear correlations were found between SPAD data and chlorophyll concentrations (<jats:italic>r</jats:italic><jats:sup>2</jats:sup> = 0.90 in benjamin fig and <jats:italic>r</jats:italic><jats:sup>2</jats:sup> = 0.91 for cottonwood). A significant, but lower correlation was found between SPAD data and N concentration. The SPAD-N correlations improved from the fifth month to the ninth month harvest (<jats:italic>r</jats:italic><jats:sup>2</jats:sup> = 0.32 to 0.53 for benjamin fig and 0.26 to 0.42 for cottonwood). The SPAD-502 could be useful for in landscape plant management, and in time for production situations, but baseline data is needed. Consistent protocol in sample collection and seasonal timing is needed prior to use as a predictor for tissue N levels. Development of species, and perhaps cultivar, specific baseline data and sampling procedures will need development, but could yield a rapid, quantitative, in expensive field diagnostic for foliage quality for making cultural management decisions.</jats:p>

Can soil plant analysis development values predict chlorophyll and total Fe in hybrid poplar?

“…2b). These were lower than the coefficients of determination obtained by Loh et al (2002) for P. deltoides (r 2 = 0.96 using a quadratic regression model) who achieved SPAD readings at the upper level of chlorophyll content in the high 30s to mid 40s, with some values exceeding 50 when sampling single fully expanded leaves.…”

“…In P. deltoides, Loh et al (2002) found a high relationship between SPAD values and chlorophyll (sampled from the first fully expanded leaf; r 2 = 0.96) but lower relationships when SPAD values were linked to N measurements (composite of six leaves per plant; r 2 = 0.42 at 5 months and r 2 = 0.26 at 9 months). Recently, in trembling aspen (P. tremuloides, Michx), Bonneville and Fyles (2006) showed a similar relationship between SPAD values and N reported as a coefficient of correlation of r = 0.63 (r 2 = 0.40).…”

“…In plant nutrition studies, the SPAD meter has been successfully used to estimate nitrogen status in apple (Neilsen et al 1995), tomato (Sandoval-Villa et al 2002, red maple (Sibley et al 1996), and corn (Smeal and Zhang 1994) among other crops (Schepers et al 1998). Loh et al (2002) used a SPAD meter to quantitatively evaluate Populus deltoides foliage quality and calibrated the instrument based on chlorophyll and nitrogen content.…”

“…Our research group has used the SPAD meter to rank Fe chlorosis in hybrid poplar test plots at the NMSU Agricultural Science Center, Farmington, a semi-arid site of elevated soil pH located in the San Juan River valley of northwestern New Mexico. Although the instrument generally indicates an objective ranking, Loh et al (2002) suggests that it may be important to calibrate the SPAD meter to differing cultivars within the same genus.…”

Composted biosolids as a source of iron for hybrid poplars (Populus sp.) grown in northwest New Mexico

“…Nitrogen influences on SPAD values and growth, which have been seen in other Populus studies (Loh et al 2002), were thought to be minor because all plots were similar for soil NO 3 -N (experiment wide mean 7.6 mg kg -1 ) and foliar total N (experiment wide mean 3.0%) (Tables 3, 4). Likewise, no differences were found with regards to soil and foliar K, Zn, and Cu (Tables 3, 4) or foliar P (Table 4).…”