The Use of Olivine for the Correction of Magnesium Deficiency in Sugarcane

Abstract

Olivine basalt has been frequently used in several countries as a source of magnesium for several crops. It contains considerable quantities of silicon and iron, as well as magnesium. Olivine is considered by some authors as being easy to weather. As olivine is an abundant material in the Hawaiian Islands, a field experiment was planted on the Island of Kauai on a Kapaa Silty Clay Soil, an Aluminous Ferruginous Latosol, in order to test its value as a cheap course of magnesium for sugarcane. Kekaha Dune Sand, a beach sand which contains fairly large amounts of olivine, was used to test that possibility. The experimental treatments were (a) no magnesium applied, (b) 500 pounds per acre of magnesium as olivine, (c) 2,500 pounds per acre of magnesium as olivine, and (d) 500 pounds per acre of magnesium as Epsom salt. Other essential elements—N, P, K, Ca, S, B, Mo, and Zn—were supplied in quantities thought to be adequate for sugarcane. The experiment was harvested at 23 months of age, and the pertinent samples were taken to determine the weight and quality of the cane. Soil and plant samples were taken at the middle and end of the crop cycle in order to find out the effects of the treatments on the soil and on the cane plant. The results of the harvest of the experiment showed no statistically significant response of sugarcane to the application of magnesium when applied either as olivine or as Epsom salt. The levels of magnesium both in soil and in plant were found to be adequate. In plants, the magnesium levels showed a steady increase with age of crop. The cation exchange capacity and the pH of the soil were not affected by the treatments. The very low levels of extractable Si in soils and plants suggested the possibility of a silicon deficiency in the soil. In general, the statue of the other nutrients in soils and plants was found to be adequate for normal growth of sugar cane.