Agro climatic suitability assessment of potato (Solanum tuberosum) winter cropping system in Kerman province

Climatic suitability evaluation is the appropriate method which be used to extend specific cropping systems and risk management of environmental stress such as drought, cold and heat at regional scale. Winter cropping system of potato is a new cropping system in some area of Iran which its production at spring season is contemporary with planting time of main potato cropping systems overall this country, so extending of this cropping system is very important to fill the market gap of this commodity. This study was conducted in order to Agro climatic suitability assessment for winter cropping system of potato (Solanum tuberosum) using analytic hierarchy process (AHP) method and geographical information system (GIS (in Kerman province.
Climatic database was made base on common historical period data (1989-2007) of maximum and minimum daily temperature, wind speed, precipitation, relative humidity and sunshine from all synoptic and climatology stations overall catchment area. Climatic indices which used to suitability assessment for winter cropping system of potato includes of: length of growing period, heat requirement, photoperiod requirement and the risk of thermal stress. Start, end and length of growing period were determined based on ecological tolerance threshold and long term climatic database. Thermal and photoperiods requirements were calculated using physiological days index. Thermal stress which includes of heat, chilling and frost was evaluated during growing period over the study area. Slope layer was created from digital elevation model with cell size of 250 meter using ArcGIS9x. Statistical analysis includes of regression modelling, correlation coefficient between climatic indices and elevation and other statistical indices was performed using SPSS software. Spatial analysis and geo statistical analysis was performed using related ArcGIS extensions. Weighting value of created spatial layers was determined using analytic hierarchy process. At the final step agroclimatic layer were overlaying to present suitability for winter cropping system of potato in Kerman province.
Results showed maximum length of growing period (110-140days) was been in Kahnouj, Jiroft and Bam stations and its minimum was been in Baft and Shahre-Babak Stations. Evaluation of thermal stress showed occurrence probability of cold stress was less than 15-20% in some area of southern region and its probability was very high in elevated area of northern, western and central region of Kerman province. Based on results of this study the station of Kahnouj has the highest risk of heat stress (25%) for potato production at spring, heat stress probability of Jiroft and Bam stations were 20% and 7% and heat stress risk in other stations were very low. Physiological day’s evaluation which used as the index for heat and photoperiod requirement showed lowest amount of this index was zero (station of Baft and Shahre-Babak) and highest amount of that was 130days (station of Kahnouj). Based on results of weighting with analytic hierarchy process (AHP), the indices weight of physiological days, frost stress probability, chilling stress probability, heat stress probability and slope were estimated 0.4206, 0.2028, 0.1947, 0.138, and 0.0439 which estimating consistency ratio was 0.035.
Result of agro climatic zoning using analytic hierarchy process showed some of southern and eastern area of Kerman province were climatically suitable for winter cultivation of potato but elevated area of western and central regions were not suitable. Eastern region of Kerman includes Dashte-Loot due to specific ecological condition have no ability for agricultural land use. In summary results of this study presented potential suitable area for winter cultivation extending with their risk climatic stress.