Oil palm (Elaeis guineensis) root growth in response to different fertilization practices

Abstract
Studying oil palm root distribution, especially the distribution of fine roots, and its
response to different management practices could give a better management
approach for the oil palm plantation, particularly for the efficiency of fertilizer
application. The aim of our study was to observe root distribution of oil palm in
response to short term change of nutrient availability caused by change in fertilizer
application as well as the differences caused by long-term management.
The root assessment was conducted on 12 years old oil palm in Ramin village,
Kumpeh District, Jambi Province, Indonesia. Two different fields were assessed; the
previously poorly managed and better managed fields. Two plots were established
in each field, one with best management practice (BMP plot) and the other one
continue with their practice as reference (REF) plot. Auger sampling method was
used to assess oil palm root distribution at different zones (circle and frond stack
zones), and different depths (0-15cm and 15-30cm) on those different plots. Root
length density (RLD), root dry matter (RDM) and specific root length (SRL) were
calculated and compared for different root classes (primary, secondary and fine
roots). Ingrowth method was used to see the differences of root growth between
the soil with more nutrient availability and the current soil
The results show that the RLD and RDM in the circle zone were higher than in
frond stack zone for all root classes except for RLD of fine roots. Both RLD and RDM
are also higher in the first 15cm soil depth compare with 15-30cm depths in frond
stack zone. Conversely for SRL value, it was significantly higher in frond stack for
secondary and fine roots but not for primary roots. The SRL values were the same
between roots in 0-15cm and 15-30cm depths except for secondary roots in the
frond stack zone. The differences between BMP and REF plots were only
significant in secondary roots (both for RLD and RDM) in frond stack zone, but the
SRL for all root classes in REF plot were significantly higher than BMP plot for roots
in the frond stack zone. No differences were observed between good and poor
managed fields. Additionally also no significant differences were observed between
roots in fertilized ingrowth bag and control ingrowth bag.
The results confirmed that oil palm root density decrease with distance from the
tree as well as with depth of soil except for the fine roots that have similar density
between the circle and the frond stack zone at the first 30cm soil depth. This result
suggests that for the adult oil palm tree, the area outside the circle zone is as
important as circle zone for root’s water and nutrients uptake. Higher SRL of fine
roots in the REF plot suggests higher plasticity of fine roots in the reference plots
but could also suggest that fine roots in the BMP plots has higher biomass per cm
root length as a response to chemical fertilizer application