Nutrient uptake of hybrid poplar in competition with weeds using the soil supply and nutrient demand (SSAND) model

Abstract

Mechanistic nutrient uptake models can help gain a quantitative understanding of nutrient uptake by plants under weed-competing conditions. The objectives of this study were to check the applicability of the soil supply and nutrient demand (SSAND) model to predict N, P and K uptake by hybrid poplar (Populus deltoides × Populus × petrowskyana var. Walker) grown with and without competition with dandelion (Taraxacum officinale) and quackgrass (Elymus repens) in a controlled environment, and to determine if incorporating N mineralization into the model would improve N uptake predictions. Simulation results showed that N uptake was underestimated for hybrid poplar by 58 to 73%, depending upon soil type and weed treatment. Incorporation of N mineralization as a model input improved the hybrid poplar N uptake predictions by 24 and 67% in the pasture and alfalfa soil, respectively, when grown without weeds. The SSAND model underestimated P uptake by 84 to 89% and overestimated K uptake by 28 to 59% for hybrid poplar depending upon the soil type and weed treatment. Results from this study illustrate that modeling competition between two species in a controlled environment study is a complex process and that further work is required to understand the underlying processes controlling nutrient supply and uptake in these systems. Key words: Nutrient uptake modeling, SSAND model, hybrid poplar, weeds, sensitivity analysis