Author(s)

E. A. Nuppenau

Abstract

Many farming areas in the semi-arid tropics and sub-tropics are characterized by increasing salinity. Due to (1) the common property problem of the media, water, (2) high transaction costs in soil protection and (3) non-point-pollution problems, salinity is a common feature of poorly managed irrigation schemes. Environmental regulations, governing water use, and farm practices such as (1) limitations in water dosage, (2) specific plants mixes, etc., but also (3) regeneration of soils, by methods such as (4) fallowing, (5) tree planting, (6) applying gypsum, etc., are normally not in the direct interest of small-holder farmers. Such measures reduce current income and future benefits have to be shared. In contrast as a new idea, tree planting to extract salt and minimize shocks from droughts have gained the interest of salinity management, notably as a low cost and appropriate technology solution. This paper presents an innovative model that accounts for salinity in the short and long run; introduces mandatory tree planting to farmers for salinity reduction; and reckons current income waivers from reduced cropping for trees. A dynamic concept is used to control farm activities and cater for a reduction of salinity in communities. It models water tables, tree cover and salt content. Keywords: tree planting, salinity, dynamic optimization. 1 Introduction In irrigation projects the salinity of soils is a serious and complex problem for resource economics [1]. Salinity threatens agricultural production in many areas of the tropics and subtropics. Though gypsum application and leaching are possible treatments [2] they are mostly too expensive for farmers. However, salinity may change through soil improvements associated with fallowing and

Keywords

tree planting, salinity, dynamic optimization.