Growth Analysis of ‘Plumosa Compacta’ Juniper and ‘Coral Beauty’ Cotoneaster Subjected to Different Nitrogen Fertilizer Regimes

Abstract

Abstract ‘Plumosa Compacta’ juniper (Juniperus horizontalis Moench.) and ‘Coral Beauty’ cotoneaster (Cotoneaster dammeri C. K. Schneid.) were container grown in a bark:peat-sand medium (2:1:1 by vol.). Plants received either 70, 140, 280 or 420 mg (0.003, 0.005, 0.010 or 0.015 oz) N per week from nutrient solutions. Growth was assessed on plants harvested from each treatment regime on May 22 and then at monthly intervals until September 16. Juniper plants grown with 140 mg (0.005 oz) N per week were larger at the end of the season than those in the other treatments. In cotoneaster, growth increased as weekly N application increased from 70 to 420 mg (0.03 to 0.015 oz) N per week. Path analysis was used to quantify the effect of plant relative growth rate (RGR) during each month on RGR in subsequent months and on total seasonal relative dry weight gain (TRWG). RGR during each month significantly influenced TRWG, with the periods from June 21 to July 20, and from July 21 to August 18 exerting the greatest influence in cotoneaster. In juniper, the influence of RGR in each month on TRWG was equal. For both cotoneaster and juniper, increasing RGR during one month tended to have a negative influence on RGR during subsequent months.