Introduction

Agro-ecological Zoning (AEZ) refers to the division of an area of lend into smaller units, which have similar characteristics related to land suitability, potential production and environmental impact. An Agro-ecological Zone is a land resource mapping unit, defined in terms of climate, landform and soils, and/or land cover, and having a specific range of potentials and constraints for land use. (FAO 1996).The essential elements in defining an agro-ecological zone are the growing period, temperature regime and soil mapping unit. 

There are several systems for describing Agro-ecological zones in the Tropics. In Kenya two are used: 

• FAO classification for tropics generally, and 
• an older Kenya version which is only applicable in Kenya