Optimization of curcumin temulawak (Curcuma xanthorrizha Roxb.) on calcareous marginal land under teak

Temulawak produces bioactive compounds that have antioxidant activity and changes in its chemical composition are caused by environmental pH. Sulphur is an essential nutrient for plants and a constituent of several coenzymes and vitamins that play a role in plant metabolism. Marginal calcareous land in Tuban is generally used as teak production forest, because food crops cannot grow optimally in this land. Temulawak is a shade-tolerant plant that can grow well in conditions of low light intensity. The objective of this research is to obtain the appropriate goat manure and sulphur fertilizer dosages for temulawak planted beneath teak stands on calcareous marginal soil in order to maximize its yield and quality. The field experiment was RCBD with three replications and two factors: manure level (10, 15 and 20 t ha-1) and ZA level (0, 40, 80 and 120 kg ha-1). The results showed that a higher fresh weight of rhizomes per clump was obtained in combination of 10 and 15 ha-1 manures and 40 kg ha-1 sulphur fertilizer. Similar high yield is obtained when 20 t ha-1 of manure is applied in combination with 80 kg ha-1 of sulphur. In addition, a higher curcumin content and antioxidant activity were obtained in plant treated with 10 t ha-1 manure without S fertilizer. Similar high curcumin content and antioxidant activity of the rhizome were also obtained from rhizome treated with 15 t ha-1 of manure in combination with 40 kg ha-1 sulphur fertilizer and 20 t ha-1 manure without sulphur fertilizer.