Specific root lengths and root diameters as an indicator of nutrient uptake efficiency in oil palm (Elaeis guineensis Jacq.)

Background and aims: This study aimed to characterize the functional root traits of 4-contrasting oil palm progenies grown under different fertilization regimes, and identify the most relevant root traits associated with nutrient uptake efficiency. Methods Four 8-year-old oil palm progenies differing in potassium (K) and magnesium (Mg) uptake efficiencies were studied in a split-plot trial in Nigeria. Fertilization treatments combined three K-levels (0, 1.5, 3.0 kg KCl palm⁻¹ year⁻¹; 60% K₂O) with three Mg-levels (0, 0.75, 1.5 kg Kieserite palm⁻¹ year⁻¹; 27% MgO). Root biomass, diameter (D), length, surface, volume, and specific root length (SRL) were measured. Results Total root biomass did not differ significantly among progenies (mean = 5.23 ± 0.37 Mg ha⁻¹), but lateral and vertical root distributions revealed distinct rooting strategies within progenies for optimal mineral uptake. Effects of fertilizers applied radially close to the palm trees were observed mainly in the topsoil (0–20 cm) at 1.5-3.5m from the application zone, where root traits differed significantly among progenies. The most productive progeny, with the highest K and Mg contents, exhibited finer roots with higher-SRL and smaller-D, making it the most efficient material for mineral uptake. Conclusion Differences in root morphology and spatial distribution among oil palm progenies reflect specific adaptation strategies influencing nutrient acquisition. Identifying traits such as higher-SRL and finer root diameter can guide breeders for quick selection of progenies with efficient nutrient uptake and higher yield potential. This study presents a practical framework for enhancing oil palm productivity through root trait-based breeding under field conditions.