Autor:innen:
Dr. Bernhard Lucke | FAU Erlangen-Nürnberg | Germany
Dr. Hussam Hag Husein | FAU Erlangen-Nürnberg | Germany
Soil fertility must be viewed as dynamic concept that changes with conditions prevailing in a region, resulting from biological, chemical, and physical processes that involve the constant cycling of nutrients between organic and inorganic forms. In this context, it refers not only a soil's ability to provide essential nutrients, but also to supply adequate amounts of water for plant growth. Soil fertility under arid and semi-arid conditions is constrained by extreme temperatures, as well as by low water availability. With some exceptions, dryland soils are characterized by small soil organic matter contents, inherently leading to low availability of nitrogen and phosphorus; and by high pH, and base saturation of 100%. The latter, if associated with excess availability of cations, may cause soil salinity. Most fertility assessment systems are based on organic matter contents as main parameter in numerical estimates of soil fertility, as organic matter not only serves as major cation exchange asset, but also stores water, and improve aggregate structure and the physical condition of soils to the benefit of the soil microbiome. However, crop experiments from various irrigated arid and semi-arid soils in Syria indicate that soil productivity, i.e. the capacity of soils to produce crops per unit area, is less affected by organic matter contents of than assumed in existing soil fertility classification systems. Therefore, we propose a new soil fertility system for dryland soils. It is a rule-based set of algorithms, mainly using additions and subtractions as in the German system, which integrate soil, climate, and landscape factors to calculate a numerical fertility value of 0-100 of a given soil. We expect the system, which is focuses on soil properties that keep or increase optimum soil moisture (such as texture) as main parameters, to be applicable in any semi-arid and arid environment and to provide more realistic estimates of fertility with regard to agricultural purposes. The presentation will briefly outline the main aspects of the system, illustrated by various case applications in Syria.