The Effect of Nitrogen and Phosphorus Ratios and Electrical Conductivity on Plant Growth

Abstract

Environmental concerns surround the use of plant growth retardants (PGRs) for plant height control, and non-chemical alternatives to PGRs can be labor intensive and expensive. Macronutrient modification is a little-studied, yet potentially effective method of controlling plant height. A number of studies have suggested that phosphorus (P) limitation may restrict plant height. Anecdotal evidence also suggests that using nitrate (), rather than ammonium ( ), as the principal nitrogen (N) source may help control plant height. The primary objective of this study was to evaluate different ratios of , /P and /P as well as electrical conductivity (EC) on plant height and growth. This was tested in a hydroponic system using marigolds, sunflowers and tomatoes. Initially, different ratios were tested at an EC of 1.2 dS∙m−1, followed by using the same ratios at four ECs (0.6, 1.2, 2.2 and 4.0 dS∙m−1) as a second objective...