2. Materials and methods
The initial approach was to study the existing information available on estates already planted with oil palm on peats in the in Sibu Sarawak, Malaysia. An area of about 11,970 ha were selected on areas already planted with oil palms and palms are now matured. A reconnaissance soil map of the estates in the region at a scale of 1:125,000 published by the Department of Agriculture and geological and vegetation maps were studied. A semi-detailed soil survey using an intensity of one auger examination point for every 20 hectares was carried out using a system of free traversing for the whole area involved. At each examination point the soil was examined using Maculay peat auger and Jerret soil auger to a depth of 125 cm or to the underlying mineral subsoil layer.
Soils were described and identified using the Malaysian Soil Taxonomy Revised Second Edition [18] and Keys to Identification of Malaysian Soils [19]. The classification of the soils was also compared with the USDA Soil Taxonomy [12] as an equivalent classification for purposes of international comparison.
Following the semi-detailed soil survey, a complete randomized design involving fields of five type of soils i.e. Naman (Typic Haplosaprist-No wood),Telong (Typic Haplosaprist-decomposed wood), Bayas (Typic Haplohemist-decomposed wood), Gedong (Typic Haplohemist-undecomposed wood) and Bako (spodosol) were used on plot size of between 60-110 hectares as described in Table 1. Uneven replications of four to six plots for each type of soil were used in the study. Criteria for selection of treatments were standardised for fair comparison of treatments i.e. Fields with same age of planting and same type of planting material were selected for the above purpose. The selection of Bako series (sandy podzol) is based on the fact that this is the only significant mineral soil available within the same locality on these peat areas. This soil was selected to make a comparison of the four peat soils with a mineral soil available at the same locality.