Kajian Ketahanan Penetrasi Tanah Akibat Residu Frekuensi Pemupukan Anorganik Pada Tanah Ultisol Perkebunan Kelapa Sawit

Abstract

Oil palm (*Elaeis guineensis* Jacq.) is an important plantation commodity, the productivity of which is influenced by the quality of the root-zone environment. This study aimed to examine soil penetration resistance in Ultisols with varying histories of inorganic fertilizer application frequency, and its relationship with soil physical properties and management zones. The research was conducted from April to June 2026 at PT Mekar Agro Sawit, Batang Hari Regency, Jambi Province, using a survey method with stratified systematic sampling. Observations were carried out across eight plant age groups (1–15 years)—representing cumulative fertilizer application frequencies ranging from 2 to 30 times—three slope positions, and two management zones (the palm circle and the inter-row area), resulting in a total of 48 observation units. Parameters measured included penetration resistance, bulk density (BD), total pore space (TPS), soil moisture content, organic matter (OM), and soil texture at a depth of 0–30 cm. The results indicate that as plant age and the cumulative frequency of historical fertilizer application increase, both penetration resistance and bulk density rise, while total pore space and soil moisture content decline. In the palm circle, penetration resistance at a depth of 10 cm increased from 14.16 to 28.21 kgF cm⁻², while at a depth of 30 cm, it rose from 22.66 to 34.56 kgF cm⁻². The palm circle zone exhibited higher penetration resistance compared to the inter-row area. The soil texture was predominantly sandy loam. The increase in penetration resistance is associated with higher soil compaction and lower soil moisture content. These findings indicate a shift in the mechanical condition of the soil in older plantations, though they do not yet establish a direct causal link between the frequency of inorganic fertilizer application and soil penetration resistance