Assessing Soil Compaction with Two Different Methods of Soil Bulk Density Measurement in Oil Palm Plantation Soil

Method comparison of soil bulk density value as an indicator of soil compaction was studied in oil palm plantation soil, as oil palm tree has high root occupancy in the soil and is estimated has high difficulty in soil bulk density sampling process. The study was compared the value of soil bulk density extracted by volumetric cylinder and rectangular box. The samples were obtained from one, five, ten, and fifteen-year age of oil palm plantation as well as natural forest. Sampling processing were conducted at front stack zone, circle zone and harvesting zone with 0-10 cm, 10-20 cm, and 20-30 cm of soil depth. Soil bulk density measured from volumetric cylinder is 6.83% higher than measured from rectangular box with root correction. Being compared to soil bulk density from rectangular box without root correction, bulk density from volumetric cylinder is 8.42% higher. Oil palm root evidence trapped in the rectangular box show a significant difference impact to the bulk density value in which the value with root corrected was higher than uncorrected one. The biomass of oil palm root in the rectangular box was found higher in fifteen years ages, indicated the difficulty of soil sampling using this apparatus compared to five and ten years age of oil palm plantation. Comparing sensitivity of the apparatus revealed that rectangular box confirmed the heterogeneous condition in the field than volumetric cylinder. Sensitivity of both apparatus was significantly difference in loamy and clay loam soil texture, while the sensitivity in sandy loam soil was not significantly different from loamy and clay loam soil texture.