Influence of Mineral Deficiencies on Growth and Composition of Vanilla Vines

Abstract

A root rot disease is the most important factor limiting commercial production of vanilla [Vanilla fragrans (Salisb.) Ames] in Puerto Rico. According to a survey of growers in 1945 (1), the disease was responsible for 40% to 50%o death of vines. In 1927 the causal organism was identified as Fusarium batatatis var. vanilae, Tucker (5). The disease usually becomes more pronounced during the third or fourth year when the first heavy crop of beans is developing. Dry weather, and possibly some mineral deficiency, appear to aggravate the disease, particularly if mulch and shade are inadequate. The purpose of the work reported here was to determine the effect of mineral deficiencies on the growth and composition of the vanilla plant, especially the effects on root growth, with a view to applying this information in the study of the root rot problem. Materials and methods The experiment was initiated in March, 1945 in a lime-coated greenhouse admitting about 50%o sunlight. The vanilla plants were grown in 5-gallon, glazed-stone crocks containing thoroughly washed and sifted pea-size creek gravel (fig. 1). Two plants in each crock were established from 6-node cuttings of about equal vigor and girth. Each crock was equipped with a 1-inch hole at the bottom for drainage. Nutrient solutions were forced into the crocks once daily by a system of iron pipes, rubber and glass tubing, and a compressed-air electric pump, similar to the system described by KIPLINGER and LAURIE (3). The vanilla plants were trained on a bamboo lattice. Cured bamboo is hard and relatively inert, making it difficult for the vanilla to obtain nutrients through the attached aerial roots. The full nutrient and deficiency solutions of nitrogen, phosphorus, and potassium were prepared according to HOAGLAND and ARNON (2) and renewed once every 2 weeks. Each treatment consisted of three replicates with two plants per replicate. Solution in the bottles was brought to the initial level once a day by additions of distilled water. The pH of all solutions was maintained at 6.0 by additions of weak solutions of either sulfuric acid or sodium hydroxide twice a week. On May 6, 1946 the experiment was terminated and growth measurements , fresh and dry weight of the plants, and mineral composition of the leaves were determined. 291