A mathematical model is formulated and implemented for the nitrogen (N) cycle, on a yearly time scale, in an arid-zone fallow system. The model is generally applicable to such systems; by combining data from a number of sources, its behaviour is investigated for a generic Sorghum bicolor — Acacia senegal system. The model reproduces such observed effects as the initial fall in soil N early in the Acacia rotation, and provides support for the hypothesis that the N fixing potential of Acacia roots is less important than their ability to take up otherwise inaccessible mineral N through deep roots.
ROBERTSON, W.H. (1994). Modelling soil nitrogen levels under acacia/sorghum rotations. Agroforestry Systems. 27 (3) pp. 283-292 [DOI: 10.1007/BF00705062]