Models of plant nitrogen uptake often lack parameters that account for either the release or immoblization of N in the soil by microbes. In addition, the role of mycorrhizal association with the plant root system and how such a symbiosis affects N acquisition is poorly integrated into models of plant N uptake. Here we suggest that development of robust models of N uptake require effective integration of microbial parameters. This will be true even in cases when the target systems are heavily fertilized. Furthermore, we argue that plant roots show a remarkable degree of adjustment in kinetics of N uptake under different environmental conditions. These adjustments must be characterized and then effectively incorporated into models of N uptake. We will also present evidence that in most agricultural as well as native systems, a substantial proportion of soil available N is present as dissolved organic N (DON) such as amino acids. These, relatively small organic N compound, can be directly acquired as an N source hence, affect plant demand for N, or alternatively, they can alter kinetic properties of root ammonium and nitrate transporters. Therefore, the reliability of N uptake models can be significantly improved if the role of DON is addressed. Lastly, we must consider how these different forms of N aretransported in soil among organic matter pools, microbes, roots, and mycorrhizae. Diffusion heavily dominates over mass flow in all cases, but the various forms of N differ significantly in diffusion kinetics.