Effectiveness of Merapi Volcanic Ash Ameliorant in Improving Chemical Properties of Ultisol Soil and Growth of Soybean.

Abstract

This research was carried out to study the effect of Merapi volcanic ash in improving chemical properties of Ultisol soil and its influence on the growth and production of soybean. The volcanic ash largely consist of minerals, such as glass volkan, labradorite, augite, bitownite, hiperstine, and hornblende with high total composition elements including Ca, Na, K and Mg that are potential to increase reserves of minerals, enrich chemical composition and physical properties of soil. The volcano ash was given on the Ultisol soil which is infertile. In this work, amelioran volcanic ash was applied at dosage of 0; 2.5; 5; 10; 20; and 40 t/ha. The result showed that the addition of Merapi volcanic ash did not increase the soil pH. However, the higher the dose of the applied volcanic ash the higher the value of Cation Exchange (K, Ca, and Mg) and Cation Exchange Capacity gained. In addition, the volcanic ash can reduce the acidity (Aldd and Hdd) of Ultisol soil. Plant tissue analysis showed that most of the N, P, and K nutrients were present in soybeans, while most of the Ca and Mg were in the leaves with the highest nutrient uptake in a dose of 20 t/ha. Merapi volcanic ash application can increase plant height, leaf number, and soybean yields with the best dose of 20 t/ha.