Researcher(s)
- Jacob Fay, Wildlife Ecology and Conservation, University of Delaware
Faculty Mentor(s)
- Alexandra Huddell, Plant and Soil Sciences, University of Delaware
Abstract
Key to understanding how nitrogen flows through agro-ecosystems is the ability to accurately analyze the nitrogen content of crops inhabiting said ecosystems. In the past, identifying the nitrogen content of a plant depended on the use of expensive and time-consuming destructive-sampling techniques. However there is a growing pool of evidence that non-destructive methodologies, particularly the use of tools like the SPAD meter, have the potential for inexpensive and rapid analysis of crop nitrogen status (Blackmer & Schepers, 1994a; Chapman & Barreto, 1997; Lin et al., 2010; Rhezali & Aissaoui, 2021). This study aimed to investigate the applicability of four SPAD value based indices, developed by Lin et al. (2010), in estimating whole plant nitrogen content of corn plants grown across a gradient of five fertilizer treatments and to develop a method for estimating total plant biomass using non-destructive sampling.
The four SPAD indices provided by Lin et al. (2010), were developed for the identification of foliar %N in rice plants and are based upon the translocation of nitrogen from older to younger leaves in cases of nitrogen deficiency. To test the usefulness of these indices in identifying the %N of corn plants several SPAD readings were taken with a Minolta SPAD Meter at three locations on the first and third fully unfolded leaf from the top of each plant, the readings from each leaf were averaged and run through the indices with the intention of looking for a correlation between the index values and the actual %N of the samples, at this time I do not have data for the actual %N. No discernible trend could be observed when comparing the index values across the different fertilizer treatments and sample time points; this may be due to intense weed competition within the plots the samples were grown in.
Biomass estimates were calculated using plant height, stem diameter,average water content and average density. Fresh mass estimates showed a strong correlation with the actual fresh masses(R² = .878) and dry mass estimates showed a similarly strong correlation with the actual dry masses (R² = .893).