Relationships of Spectral Reflectance with Plant Tissue Mineral Elements of Common Bean (Phaseolus Vulgaris L.) Under Drought and Salinity Stresses

ABSTRACT

Salinity and drought stresses are critical for Phaseolus vulgaris L. growth and development. They affect plants in various ways, including tissue mineral element content. Micro- and macro-elements in leaves of Phaseolus vulgaris L. (cv. ‘Blue lake’ and cv. ‘Terli’) subjected to deficit irrigation and salinity treatments were investigated, both analytically and with regards to their effect on the leaves’ spectral reflectance. B (boron), K (potassium), Mn (manganese), Na (sodium), Si (silicon) and Zn (zinc) appeared to be influenced by stress factors, mainly responding to salinity increase. The leaf spectral reflectance of the plants appeared to be significantly correlated with most of the elements under investigation. Multivariate regression identified a relationship of the reflectance at particular regions of the spectrum with phosphorus and NDVI (normalized difference vegetation index) and indicated a significant correlation with B, Fe (iron), K, Mn, P (phosphorus) and Zn. Moreover, customized spectral indices, exhibiting significantly high correlation with B, Fe, K, Mg (magnesium), Mn, Na, P, Zn and N (nitrogen), were developed.     

Estimating Foliar Nitrogen Concentration of Heather (Calluna vulgaris) from Field and Laboratory Spectra

Regional botanical surveys supported by field experiments suggest that atmospheric nitrogen deposition threatens the balance between species and causes loss of biodiversity within plant communities. Methods are required to monitor the nitrogen status of vegetation at a landscape scale and therefore the potential for ecological change. Remote sensing has the potential to monitor a number of plant biophysical and chemical variables, but its application to monitor the nitrogen status of native vegetation remains limited and untested. Using field spectroscopy, canopy reflectance measurements were taken from two heathland field sites and heather (Calluna vulgaris) plants grown in a greenhouse. The nitrogen concentration was determined through destructive sampling and chemical analysis. Stepwise multiple regression analysis was used to identify the wavebands most associated with nitrogen concentration and despite high variation in the selected wavebands between the three datasets, most of these wavebands were associated with nitrogen and protein absorption features within the spectral region 1,990–2,170 nm. Results highlight the potential of remote sensing as a bio-monitoring technique to estimate foliar nitrogen status in native plants.     

ELEMENTAL SULFUR IMPREGNATED WITH IRON AS A FERTILIZER SOURCE FOR KENTUCKY BLUEGRASS

Elemental sulfur (S) impregnated with Fe (S-Fe) fertilizer was evaluated on Kentucky bluegrass (KBG; Poa pratensis L.) in three glasshouse studies: (1) with/without Fe as S-Fe, ferrous sulfate (FS), or iron-ethylenediamine-N,N’-bis(2-hydroxyphenylacetic acid) (Fe-EDDHA) to soil (49 kg Fe ha^?1), or foliar Fe-EDDHA (5 kg Fe ha^?1) on two cultivars; (2) 0, 49, 197, or 592 kg Fe ha^?1 of S-Fe deep mixed or surface mixed on two soils; (3) 0 or 49 kg Fe ha^?1 applied as S-Fe on four cultivars. A field study comparing 0 and 49 kg Fe ha^?1 applied as S-Fe to KBG was also conducted. Soil applied S-Fe was assimilated in shoots as efficiently as Fe-EDDHA applied to soil or foliage. Shoot Fe increased significantly with increasing S-Fe in a curvilinear response when deep mixed with soil and in a linear response when surface applied. However, no Fe source tested impacted yield or verdure in these studies.