Potassium Uptake and Utilization Efficiency Among Selected Nitrogen-Fixing Tree Legumes Over Time

Nutrients released from tree prunings sustain alley cropping. Potassium (K) uptake and utilization efficiency were monitored over 16 months in Gliricidia sepium, Leucaena leucocephala, and Albizia lebbeck. Tree interspecific variation arose in biomass yields and K nutrition. Tissue potassium concentration narrowed within 0.68–1.15% and varied little among tree parts and species over time. Potassium accumulation increased steadily with tree age and significant differences among trees occurred at all ages. Gliricidia sepium had a higher yield than the others over the first 8 months, after which the uptake pattern declined drastically to become the lowest at harvest. Differential K partitioning within trees occurred as K in leaves, stems, and roots amounted to 18, 35, and 47% in Albizia; 28, 25, and 47% in Gliricidia; and 27, 42, and 31% in Leucaena, respectively. Higher K allocation into Leucaena stems and its low partitioning into Albizia leaves were drawbacks for alley cropping. Potassium utilization efficiency decreased inversely to biomass yield and K uptake over time. It differed significantly among trees with Albizia being the most efficient. Low K returns from tree prunings in alley cropping could be due to its uptake potential and partitioning impairment in each species.