Wednesday, November 15, 2006

Soil Supply and Nutrient Demand (SSAND) Model - Tool for Predicting N Uptake for Hybrid Poplar in Competition with Weeds.

Bachitter S. Kabba1, Diane Knight1, and Kenneth C. Van Rees2. (1) Dept of Soil Science, 51 Campus Dr, Saskatoon, SK S7N 5A8, Canada, (2) Dept of Soil Sciences, Saskatoon, SK S7N 5A8, Canada

Nitrogen (N) uptake modelling using mechanistic model can help us in better understanding of the processes that govern nitrogen supply in the soil and uptake at the root surface, particularly in weed competition scenario. Therefore, the objective of this study was to simulate N uptake in hybrid poplar and to understand the mechanisms that affect nitrogen uptake under weed competition using modeling approach.  Soil supply and nutrient demand (SSAND) model was used to predict the N uptake by hybrid poplar grown alone and along with different densities of dandelion and quackgrass weeds in a pot study. Two soils differing in N content were collected from two land management (Alfalfa and Pasture) sites near Meadow Lake, Saskatchewan. Several plant growth and soil parameters such as water influx rate, root radius, root length density, initial soil solution concentration, soil buffer power and N mineralization rate were obtained in order to provide necessary inputs for SSAND model. Simulations were carried out for two harvest periods i.e. 47 and 97 days for the Pasture soil and at 49 and 102 days for the Alfalfa soil. Initial results indicate that model greatly underestimates the N uptake for hybrid poplar in both control and weedy treatments, which may be due to inadequate description of the processes in the model that control N supply in soil to the root surface, for example, N mineralization. However, ability of SSAND model to incorporate N mineralization can help us in improving our N uptake predictions. Therefore, future work will be focused on predicting N uptake in hybrid poplar after incorporating N mineralization inputs and results will be presented.