Nitrogen factor in organic matter cycling and utilisation in arid soils

Abstract

Nitrogen affects the growth of plants and microorganisms and hence the turnover of organic matter in arid soils. The compartments and fluxes of the nitrogen cycle in arid ecosystems are described by analogy to the more readily quantified information available from work with humid ecosystems in Northern Europe. The quantity of organic matter in arid soils is extremely low and its maintenance or enhancement is vital to the rehabilitation of arid lands. A review of the transformations of nitrogen that are critical to the level of organic matter in arid soils reveals a paucity of data. It is not yet possible to construct models of the turnover of nitrogen and carbon in arid soils that would assist clarification of missing data and processes, and more importantly of the factors that control them. It is concluded that the microbiological processes of the nitrogen cycle per se are of small importance in desertification or its possible reversal. They are indicators of the health and stability of arid land systems rather than prime movers in land reclamation, the possible exceptions being nitrogen fixation and soil stabilisation by cyanobacteria. The remedies for desertification would appear to lie initially in the hands of water engineers and agronomists rather than microbiologists, but irrespective of technical skill all would require support from politicians, economists, and planners.