Growth of Southern Naiad (<i>Najas guadalupensis</i>) and Hydrilla (<i>Hydrilla verticillata</i>) using Controlled-release Fertilizer

Abstract

The native aquatic plant southern naiad (Najas guadalupensis) is often mistaken for the invasive weed hydrilla (Hy­drilla verticillata). Much information has been published on the growth of hydrilla but few studies have investigated the growth of naiad. We compared the growth of naiad and hydrilla plants fertilized with 0, 1, 2, or 4 g of controlled release fertilizer (CRF) (Osmocote 15N–4.05P–9.96K) per kg of sand, with the fertilizer layered into the sand prior to planting. We prepared three mesocosms per fertilizer rate, with 3 containers of naiad or hydrilla in each mesocosm. Mesocosms were randomly arranged in a greenhouse and filled with water to create a submersed growing environ­ment. Growth was monitored for 8 weeks in Spring 2014 and was repeated in Summer 2014. Naiad shoot and root dry weights were greatest in containers fertilized with 2 g of CRF per kg of sand, while hydrilla shoot and root dry weight were greatest in containers fertilized with 4 g of CRF per kg of sand. Although these species may look similar, it is clear from this study that their nutritional requirements are different.