Land Suitability Assesment and Crop Zoning of Bangladesh.

S G Hussain, M K A Chowdhury and M A H Chowdhury

Bangladesh soil and climatic conditions is suitable for growing wide range of both tropical and temperate crops. The major crops cultivated in the country are rice, wheat, maize, sugarcane, potato, jute, pulses, oilseeds, spices and vegetables. Cereals and potato production fulfils the country’s requirement. Other crop productions are deficient in the country. To meet the demand a huge amount of foreign currency is spent for importing sugar, pulses, oilseeds and spices every year. The deficiency of some crops can be minimized through increase of production in a suitable land with a minimum cultivation cost. For that, it is important to identify and delineate suitable area for growing particular crop in order to harvest maximum potential yield. 
The agro-edaphic and agro-climatic data of Land Resources Information System of BARC were used for land suitability assessment in order to identify and delineate suitable area for growing particular crops. Eleven agro-edaphic factors (Soil: Soil Permeability, Effective Soil Depth, Available Soil Moisture, Nutrient Status, Soil Reaction (pH), Soil Salinity, Soil Consistency, Drainage; Inundation: Depth of inundation, Flood hazards; and Landform: Slope) were considered for land suitability analysis. And the agro-climatic factors (length of kharif growing period, pre-kharif transition period, thermal zone and extreme temperature) which influence crop growth in relation to crop phenology and photosynthesis were also considered for climatic suitability analysis of different crops. The agro-edaphic and agro-climatic suitability of crops has been assessed separately based on each individual soil/land and climatic factor limitations with respect to crop requirements. This was done on the basis of expert judgment from the NARS scientists and other experts who have wide knowledge and field experience on cultivation of crops. Accordingly, agro-edaphic and agro-climatic suitability maps of different crops were produced. In the final stage, the agro-edaphic and agro-climatic suitability maps were overlaid to get the overall suitability maps of different crops. The agro-edaphic, agro-climatic and overall suitability is accomplished on the basis of Zijsvelt’s soil-crop suitability model which was introduced in 1979 revised by Brammer in 1985 and further revised by Hussain et al, 2005. The crop suitability maps thus produced show the potential areas under different class which are as follows. 
Very suitable : > 80 percent of maximum attainable yield (MAT)
Suitable: 60-80 percent of MAT
Moderately suitable: 40-60 percent of MAT
Marginally suitable: 20-40 percent of MAT
Not suitable: < 20 percent of MAT
The crop zoning maps were produced considering the percentage of the total cultivable area of the upazila under each crop suitability classes. In classifying the crop zone some criteria were followed which are described in the book “Land Suitability Assessment and Crop Zoning of Bangladesh” The crop zoning provides the opportunity to grow the selected crops in different zones according to to suitability. The upazila wise area coverages 17 crops under different suitability classes and zones were generated in tabular form. The will help devising appropriate policy for implementation of crop zoning at the upazial level.
Benefits of crop zoning
The crop zoning provides basic information for growing potential crop and deriving maximum economic benefit. The crop zoning facilitates better utilization of land and water resources thus provide opportunities to harvest full potential of the crops if grown in areas specified as suitable. The maximum yield is achievable by following the crop zoning map. It is recognized that the crop can be grown in suitable areas with lower production cost. If the same crop is grown in non suitable areas, the cost of cultivation will be higher compared to suitable areas.