Author : Winastuti Dwi Atmanto

Summary : A study on the enhancing of litter decomposition rate of Acacia Mangium Willd was conducted under a forest stand in Wanagama I, Gunung Kidul. The objectives of the study were to find the best priming organic matter to stimulate litter decomposition, to assess nutrient status of the forest floor and to quantify litter production of the A. mangium stand. A factorial experiment involving three kinds of organic matters (rice straw, king grass and alang-alang grass) and three different period of incubation (2,4, and 6 months) were laid out in a randomized completely block design with three replications. Each organic matter was applied at 3 different rates : 1/4, 1/8, and 1/16 litter weight. C, N, cellulose and lignin contents of decomposing litter in every treatment were measured. Litter production and the contents of P, K, Ca and Mg were assessed at the end of incubation time for the decomposed litter and newly-formed soil of decomposed litter. Result of the study indicated that king grass applied at 1/16 litter weight was the best "priming" organic matter with a decomposition rate (K) of 0.35. the application of king grass decreased C/N ratio from 15.34 (2 months incubation) to 9.48 (6 months incubation ) and reduced C/L content from 1.08 (2 months incubation) to 0.93 (6 months incubation). The C/N ratio of soil was decreased considerably with the addition of alang-alang grass from 22.28 (2 months incubation) to 6.15 (6 months incubation). The P and K contents of decomposed litter and those of newly formed soil of decomposed litter after 6 months incubation were not significantly different among both organic matters and the rates being applied. The applciation of king grass gave the lowest Ca content of the decomposed litter, while rice straw addition resulted in the lowest Ca concentration in the newly-formed soil were the lowest upon the application of king grass. The litter production varied from 1.70 (August) to 8.59 ton/ha/yr (May).