Judul: Pengaruh Kedalaman Muka Air Tanah dan Dosis Terak Baja terhadap Hidrofobisitas Tanah Gambut, Emisi Karbon, dan Produksi Kelapa Sawit
Abstrak: Development of oil palm plantation requires drainage to support growth and production of the oil palm. The excessive drainage would cause the peat dryness of as well as hydrophobicity and thus decreasing its capacity to retent water, soil infiltration, surface erossion. It can limit oil palm growth. The application of water management and soil amandment must be performed to avoid the decrease of peat soil quality and to improve the productivity of oil palm. This series research was designed to: 1) evaluate the peat soil hydrophobicity under oil palm plantation area, 2) study the effect of the ground water level depth and stell slag dose on the peat soil hydrophobicity and other soil physical changes, 3) study the effect of the ground water level depth and the steel slag dose on CO2 emission from peat soil, and 4) study the effect of ground water level depth and steel slag dose on the growth and production of oil palm. The first study has utilized sapric and hemic peat soil samples taken from the 6-year Panai Jaya Oil Palm Plantation (PAJ) and the 20-year Meranti Paham Oil Palm Plantation (MEP). Peat soil samples were heated at a temperature of 50°C with a time interval and the effects on hydrophobicity were recorded. Hydrophobicity of the peat soil was evaluated by Water Drop Penetration Time (WDPT) method. After the hydrophobicity of all peat soil samples had been observed, a number of soil properties, including soil water content (SWC), total acidity, carboxylic content (COOH) and phenolic-OH were then analyzed. Critical water content (CWC) of the peat soil. The point at which hydrophobicity occurred, was determined using exponential relationship between soil water content and the probability of the occurrence of soil hydrophobicity, the point at which the probability of the occurrence of hydrophobicity was between 60% and 80%. Fourier Transform Infra Red (FTIR) spectrometer was used to evaluate peat soil hydrophobicity by knowing the functional groups in peat soil. The second experiment was carried out in laboratory by application of various steel slag level (0; 7.17; 14.81; dan 22.44 g pot-1) on two peat type (sapric dan hemic) with two soil moisture conditions including wet and dry (hydrophobic). Peat soil samples that has been added with steel slag incubation for 60 days and observation of soil properties, FTIR analysis, and wettability by WDPT method. The field experiment was carried out in 6 years-oil palm block of PAJ. Research plots was designed using a split plot design with three replications. Plots treated with three treatments of ground water level (MAT-1, MAT-2, and MAT-3) as main plots and four level of steel slag application (0; 3.15; 6.51; 9.86 kg pohon-1) as a subplot. MAT-1 is ground water level (GWL) at depths of 30-50 cm, MAT-2 is GWL at depths of 60-75 cm, and WLM-3 is GWL at depths 70-90 cm below the soil surface. The research observation consists actual soil water content, actual v hydrophobicity, oil palm growth and production, subsidence, and accumulation of heavy metals in fruit. The results shown that hydrophobicity of peat soil in this study was
Keyword: CO2 emission, hydrophobicity, oil palm, peat soil, steel slag