Genotype–nutrition interactions in field-planted loblolly pine

Four families of loblolly pine (Pinustaeda L.), representing a productivity gradient, were compared to determine inherent differences in productivity and nutrient efficiency for two nutrient regimes. The nutrient regimes consisted of a nonfertilized treatment, representing a deficiency of N, P, and K, and a fertilized treatment, ensuring an adequate supply of N, P, and K. Nutrient efficiency was determined using the traditional measure of nutrient use efficiency and alternative measures, including biomass and nutrient accumulation over time, element ratios, specific absorption rate, internal translocation, and a graphical technique. Family and nutrient regime differences were found in biomass production, biomass allocation, and nutrient efficiency. Of the nutrient efficiency measures, biomass and nutrient accumulation, nutrient use efficiency, and specific absorption rate tended to mirror family productivity differences. Family variation in element ratios, internal translocation, and the graphical technique did not mirror biomass production and, thus, were able to provide additional information on specific nutrient use mechanisms of efficiency that is not provided by traditional nutrient use efficiency calculations, the latter being confounded by biomass production.