Modeling Nitrogen Uptake in Oilseed Rape cv Capitol during a Growth Cycle Using Influx Kinetics of Root Nitrate Transport Systems and Field Experimental Data

The use of kinetic equations of NO3- transport systems in oilseed rape (Brassica napus), determined by 15NO3labeling under controlled conditions, combined with experimental field data from the INRA-Chalons rape database were used to model NO3- uptake during the plant growth cycle. The quantitative effects of different factors such as day/night cycle, ontogenetic stages, root temperature, photosynthetically active radiation, and soil nitrate availability on different components of the constitutive high-affinity transport systems, constitutive low-affinity transport systems, inducible low-affinity transport systems, and inducible high-affinity transport systems of nitrate were then determined to improve the modelʹs predictions. Simulated uptake correlated well with measured values of nitrogen (N) uptake under field conditions for all N fertilization rates tested. Model outputs showed that the high-affinity transport system accounted for about 89% of total NO3- uptake (18% and 71% for constitutive high-affinity transport systems and inducible high-affinity transport systems, respectively) when no fertilizer was applied. The low-affinity transport system accounted for a minor proportion of total N uptake, and its activity was restricted to the early phase of the growth cycle. However, N fertilization in spring increased the duration of its contribution to total N uptake. Overall, data show that this mechanistic and environmentally regulated approach is a powerful means to simulate total N uptake in the field with the advantage of taking both physiologically regulated processes at the overall plant level and specific nitrate transport system characteristics into account.