Physical changes to oil palm empty fruit bunches (EFB) and EFB mat (ECOMAT) during their decompostion in the field

The main objective of this study was to determine the physical changes to oil palm empty fruit bunches (EFB) and EFB mat (Ecomat), used as soil mulching materials, during their decomposition in the field. The field experiment was conducted at an estate with nine-year-old oil palm trees and with a hill slope of 6°. The experimental design was a Randomized Complete Block with two treatments (EFB and Ecomat) and three replications. For each replication, EFB was applied as a single layer on the soil surface at a rate of 1000 kg palm-1. Ecomat was applied as a single layer of four carpet pieces, arranged side-by-side and without gaps between the pieces. Each piece of Ecomat carpet had an area of 1 m² and an average thickness of 20 mm. Data was collected every two months interval for six months. Physical properties of EFB and Ecomat measured were bulk density, water content, water retention, and saturated hydraulic conductivity. Additionally, soil water content up to 750 mm depth was measured daily. The mean thickness of EFB and Ecomat at the start of the experiment were about 120 and 20 mm, respectively. For EFB, its thickness reduced at a rate of 15.0 mm month-¹, whereas for Ecomat, at a slower rate of 2.4 mm month-¹. It was estimated using linear regression equations that both EFB and Ecomat would fully decompose in slightly over 9 months. Results also showed that as compared to Ecomat, EFB had a lower bulk density, higher saturated hydraulic conductivity and higher water content. EFB also held its water more strongly than Ecomat. All these properties helped the soil treated with EFB to have more water than the soil treated with Ecomat. Ecomat was, on average, two times more compact than EFB (0.24 Mg m-³ for Ecomat against 0.11 Mg m-for EFB). Bulk density for both materials, however, would not significantly change over time. Nevertheless, saturated hydraulic conductivity (K) for EFB was, on average, two times higher than for Ecomat, and the K for both mulching materials would decrease by over two times over time. EFB also contained more water (by 26.6%) and held the water more strongly than Ecomat. Lastly, the soil under EFB mulch had, on average, 16% more water than the soil under Ecomat mulch.