624 (PS 3) SOIL AMENDMENT INCREASES GROWTH OF SALVIA SPLENDENS AND CATHARANTHUS ROSEUS

Abstract

Commonly used soil amendments for ornamental annual plantings were compared to determine their effect on growth of Salvia splendens `Hotline Red' (Salvia) and Catharanthus roseus `Peppermint Cooler' (Vinca). Transplants of the annuals were planted in amended outdoor beds on June 12 1992. Treatments were 1) an unamended, rototilled control and 2) aged pine bark, 3) granite sand or 4) a regionally commercially available product Mr. Natural™. Mr. Natural™ consists of granite sand, expanded shale, and composted poultry litter. A 9-cm-deep surface layer of the amendments was rototilled into 20 cm of clay soil. One-half of the plants were fertilized with the recommended rate of 0.15 kg/m2 of 14-14-14 Osmocote, and one-half were not fertilized. On July 14 and August 10, shoot dry weight was determined, and a growth index was calculated from the width and height of growth. Fertilizing increased the growth index and dry weight in all treatments. Plants in the aged pine bark and no fertilizer treatment were consistently the smallest plants and exhibited nitrogen deficiency symptoms. For both dates, the Mr. Natural™ vinca plants had the greatest dry weight and growth index. On the first date, Mr. Natural™ salvia plants did not differ from the sand treatment but had 50% greater dry weight than the unamended control. Mr. Natural™ salvia plants were the largest plants on the second harvest date.