The zonation is based on three factors, each reflecting physical constraints on agriculture: altitude, slope, rainfall, and nutrient availability. The Ago-Ecological Zones are the intersection of the inputs and broken up into categories. The Regions are the simplified version of the Zones and represent more general Land Systems. Four regions and 18 zones were delineated as follows: Region 1 – Mountains above 1000m subdivided into zones by slope classes Zone 1 – Mountain Peaks Zone 2 – Upper Montane Zone 3 – Mid Montane Zone 4 – Lower Montane Region 2 – Hills 300m to 1000m, subdivided into zones by slope classes Zone 5 – Upper Hills Zone 6 – Mid Hills Zone 7 – Low Hills Region 3 – Inland Plains, subdivided into zones by mean elevation Zone 8 – Mean Elevation 270m Zone 9 – Mean Elevation 225m Zone 10 – Mean Elevation 175m Zone 11 – Mean Elevation 135m Zone 12 – Mean Elevation 100m Region 4 – Coastal Plains, subdivided into zones by annual mean rainfall Zone 8 – Mean Rainfall 1700 mm/yr Zone 9 – Mean Rainfall 1700 mm/yr Zone 10 – Mean Rainfall 1700 mm/yr Zone 11 – Mean Rainfall 1700 mm/yr Zone 12 – Mean Rainfall 1700 mm/yr The seven slope classes, ranging from 0 o to >25o (lowest to highest constraint) were derived from SRTM data: Jarvis, A., H.I. Reuter, A. Nelson, E. Guevara, 2008, Hole-filled SRTM for the globe Version 4, available from the CGIAR-CSI SRTM 90m Database at http://srtm.csi.cgiar.org. The six mean annual rainfall classes, ranging from 1700 mm/yr to 4700 mm/yr were derived from Hijmans, R.J., S.E. Cameron, J.L. Parra, P.G. Jones and A. Jarvis, 2005. Very high resolution interpolated climate surfaces for global land areas. International Journal of Climatology 25: 1965-1978. Data accessed at http://www.worldclim.org. The six nutrient availability classes were based on geological substrate. In rank order, these were alluvium (least constraint), sedimentary, metamorphic and volcanic, granitic, limestone and ultrabasic, and water bodies (highest constraint). The source was Suntac Technologies, 2001. Geology of the Union of Myanmar, Digital Agricultural Atlas of Myanmar.