Influence of High, Medium, and Low Soil Moisture on Growth and Alkaloid Content of Cinchona ledgeriana

Abstract

Soil moisture in Cinchona growing regions may fluctuate greatly with seasonal changes in rainfall; prolonged droughts are experienced almost annually. On the other hand, during the peak of the rainy season the same soils may remain at or near saturation for extended periods. For example, at the Toro Negro National Forest in Puerto Rico, where Cinchona is being grown experimentally, the 23-year-average rainfall for two-week periods from January 1 to March 25 was 2.04 inches with frequent periods of drought. In the current year only 0.21 inch fell during January. From August 13 to November 18 rainfall averaged 5.69 inches for two-week periods. The average total annual rainfall for 23 years was 96.37 inches (4). The above extremes in soil moisture may be expected to exert marked influence on the growth and composition of Cinchona. Heinicke, Boynton and Reuther (3) demonstrated that a flooded (poorly aerated) soil produced symptoms in the apple typical of boron deficiency when the soil was not deficient in that element. It was also indicated that lack of oxygen in the soil interfered with the absorption of nitrogen and potassium. Wager (?) showed that avocado plants were more susceptible to disease if grown in a flooded soil than if watered normally. During the first year from seed, Cinchona plants are primarily herbaceous. It is during this tender stage that soil moisture is most likely to be a critical factor affecting growth. Since the plants are grown in palm-leafcovered nurseries during this stage it is fairly easy to correct a deficiency of soil water by irrigation, but more difficult to prevent an excess during the rainy season. Cinchona nursery plantings have been observed which were apparently healthy during three-fourths ?f the year, but with the advent of heavy daily rains during the peak of the rainy season the plants developed symptoms typical of nutrient deficiencies and many succumbed to fungus attack. The experiment reported here was designed to study the effect of low, medium, and high levels of soil moisture on growth and alkaloid content of young Cinchona ledgeriana seedlings under controlled conditions.