Biomass Production and Phosphorus Use Efficiency in Two Tithonia diversifolia (Hemsl.) Gray Genotypes

Little information exists on the phosphorus (P) use efficiency of Tithonia diversifolia under varying levels of soil P availability. This study evaluated biomass production, changes in tissue P concentration, P uptake, and P uptake and utilization efficiencies in a Costa Rican and Colombian T. diversifolia genotype when 0, 0.3, 5, and 30 mg P g^?1 were available. Biomass, root length and tissue P concentration increased significantly (P < 0.05) with increasing levels of P availability and with time. Phosphorus uptake (mg plant^?1) was significantly higher (P < 0.05) at 30 mg P g^?1. Phosphorus uptake (mg P mg^?1 P_f) and utilization (mg mg^?1 P) efficiencies were greatest at 0.3 and 5 mg P g^?1. Differences between genotypes showed that T. diversofilia from Colombia had a significantly higher (P < 0.05) biomass, tissue P concentration, root length, and a more effective uptake and utilization of P when availability of this nutrient was low.