Organic substrate is an important component of biological treatments for acid mine drainage (AMD) remediation systems. It provides organic substrates to sulfate-reducing bacteria (SRB) in the sulfate (SO4) reduction, resulting in increased alkalinity and metal sulfide precipitates. Natural organic matters vary in their characteristics, and therefore may perform differently for remediation properties. This study was aimed to characterize four locally available organic wastes (bark, empty fruit bunch, sawdust, and chicken manure) potential for AMD remediation. Their chemical properties and elemental compositions were measured. An anaerobic incubation of these wastes in AMD was undertaken to determine their remediation properties. The pH, electrical conductivity (EC), redox potential (Eh), and dissolved Fe and SO 4 of the mixtures were measured after the 1st, 7th, 14th, and 30th day of the incubation at room temperature. The results demonstrated that organic wastes varied in their chemical properties and performed differently in treating AMD. Organic wastes containing high alkalinity (high pH) and nutrient concentrations (chicken manure and empty fruit bunch) improved AMD quality through increasing pH (>6) and reducing dissolved Fe and SO4 concentrations. Although sawdust and bark (high CEC) did not increase pH up to acceptable standard at most time, they apparently were able to remove dissolved Fe from AMD through adsorption mechanism.

[CHANGE IN SOIL CHEMICAL CHARACTERISTICS AND YIELD OF MAIZE IN AN INCEPTISOL AS AMENDED WITH COMPOST]. Vast area of inceptisol in Indonesia is a potential natural resource for improving the domestic maize production. The amendment of organic material is expected to make correction on the fertility problem inherent in the soil. Objective of this study was to determine the optimum dose of compost for some soil chemical properties and maize performances. The doses of compost consisted of 0, 2.5, 5, 7.5, 10, and 12.5 ton/haa were allotted randomly on the experimental plots according to completely randomized design with three replications. Observations were made on  the exchangeable Aluminum (Al-dd), pH, organic carbon, water content, plant height, unhusked and husked ear weight, and grain yield. Analysis of variance showed that the dose of compost had significant (P?0.05) effects on pH and C-organic in soil. Giving compost at a dose about 12.5 ton/ha could increase the pH about 4.9, whereas giving compost at a dose about 10 tonha-1 could increase C-organic about 3.09 %. In other hand, the giving of compost with various dose did not give significantly (P>0.05) affect towards  Aluminium (Al-dd), pH, C-organic, water content, height of plants, weight of without husk, weight of cob with husk, weight of dry corn beans. The highest grain yield (2,415.75 kg/ha) was observed on compost applied at  dose  12.5 ton/ha.

The objectives of this research were to obtain an optimum dose of vermicompost fertilizer to the nutrient levels of K in the leaves, K uptake, and corn growth in ultisols. This research were held in September until November 2018, which has been implemented in green house and  the Laboratory of Soil Science, Faculty of Agriculture, University of Bengkulu. The research used   Completely Randomized Design (CRD) with a single factor consisting of 7 levels of treatment and three replicates  i.e.  0 , 2.5 , 5.0 , 7.5 , 10.0, 12.5, and 15.0 ton ha-1. The results showed that the optimum dose of vermicompost fertilizer 5.71 ton ha-1, resulting in leave K content of 0.59%,  9.5 ton vermicompost ha-1, producing  the absorption of K leaves 31 kg ha-1,   9.59 ton vermicompost ha-1, producing a plant height 160.7 cm,   10.2 ton vermicompost ha-1, producing the fresh stover weight 27,561.2 kg ha-1, 98.9 ton vermicompost ha-1, producing the dry stover weight 5,675.5 kg ha-1, and 9.5 tons vermicompost ha-1, producing root dry weight  1,156 kg ha-1.

Most of rubber plants in Indonesia are cultivated in highly-weathered soils; therefore, their annual productions are relatively low with the low quality of latex. The aim of this reseach was to increase the latex quality from a rubber plantation grown on low fertility soils by applying a locally-produced organic fertilizer (LOF) to the soils. This research consisted of two steps, i.e. LOF production and a field fertilization experiment. The LOF was made mainly from waste of a latex processing industry. The field fertilization experiment was conducted to assess the effects of LOF additions to the soils on the latex quality. The field experiment was performed using a randomized complete block design with 6 LOF levels, 4 levels of land slopes, and 5 rubber trees in each block, resulting in 120 rubber trees. The LOF levels were 0, 10, 20, 30, 40, and 50 kg tree-1. The LOF contained 17.35% organic-C, 1.14% total-N, 0.53 ppm available-P, and 1.21 cmol (+)kg-1 exchangeable-K, with slightly alkaline pH (pH 8.0). The soil has low fertility status as indicated by the low amounts of total-N and exchangeable base cations (K, Na, and Mg), and very acid pH (pH 4.5). Indicators of latex quality comprising of blockage index, ash-, impurity- and dry rubber-content, and N, P, K contents in the rubber leaves were measured. Although there were no significant differences in most observed latex properties due to LOF addition, their values tended to be higher when the rubber trees were fertilized with LOF. Apparently N and K contents in the rubber leaves are better correlated to the latex properties compared to the P content.

The low quality of Entisol is caused by low availability of nitrogen, phosphorus, and potassium as well as low soil pH, so the addition of vermicompost is necessary. The purpose of this study was to determine the effect of vermicompost application on soil quality and to obtain the highest vermicompost dosage on the availability of nutrients such as N, P, K, and the yield of corn. The field experiment used a Randomized Completely Block Design (RCBD) with 7 dosages of vermicompost and three replications. The treatments were V0 = 0; V1 = 5; V2 = 10; V3 = 15; V4 = 20; V5 = 25; V6 = 30 Mg ha-1. Variables observed consisted of 1) initial soil and vermicompost characterization analysis, 2) soil analysis and N, P, and K content in leaves, and yield of corn. The results showed that Entisol was classified as low quality; however, vermicompost quality complied with the requirements of quality organic fertilizer. The experiment also indicated that the highest pH of Entisol (5.31) and K content in corn leaves (2.12%) were obtained at a dose of vermicompost 25 Mg ha-1. Meanwhile, the highest weight of husked corn cobs (415.55 g plant-1) and weight of unhusked corn cob (351.11 g plant-1) were obtained at a vermicompost dose of 15 Mg ha-1.