AGROCLIMATIC ZONING AND PHYSICAL LAND EVALUATION IN JAMAICA

Analysis of agro-climatic conditions forms the first stage of physical land evaluation. Monthly rainfall, potential evapotranspiration and air temperature data are analysed by the agro-climatic module of the Jamaica Physical Land Evaluation System (JAMPLES). Dependable rainfall (R75), the minimum amount exceeded in a given time period in 75% of the years, ranges from 537 to 5332 mm/yr at the 141 recording stations under review, and mean potential evapotranspiration (PET) ranges from 1120 to 1580 mm/yr. Annual R75/PET ratios range from 0.3-5.0 island-wide and regional differences permit delineation of four 'moisture availability' zones. These are subdivided with respect to the length of the 'dependable' growing periods (DGP) and dry periods. The DGP is less than 2 months in the southern coastal plains and 12 months long in the north-eastern part of the island. Mean daily air temperature decreases from 26 to 13 degrees C with elevation, permitting the delineation of five temperature classes. Suitable regions for growing particular crops can be determined with the Jamaica Geographical Information System (JAMGIS), which includes a digitized version of the 1:250 000 map of agro-climatic zones. More specific land suitability assessments, taking soil conditions and feasible land management practices into account, are prepared with the physical land evaluation module of JAMPLES.