Introduction
Identifying land suitability and potential for various uses is crucial for conserving environmental resources and achieving sustainable agricultural production. The absence of systematic land-use planning can lead to significant socio-economic and environmental damage. Agro-ecological zoning, which integrates environmental data layers such as climate, water, topography, and soil, serves as a vital tool for agricultural planning. It allows for a comprehensive analysis of production possibilities by assessing environmental potentials and constraints, thereby enabling informed decision-making. In Iran, despite the agricultural significance of many regions, the environmental potential of most areas has not been scientifically delineated. This study was conducted to perform detailed agro-ecological zoning and estimate the production potential for rice (Oryza sativa L.) in the Yaneh-Sar District of Behshahr County, Mazandaran Province – a region with a distinct, cooler climate compared to other parts of the province, which has faced developmental challenges and agricultural issues such as declining yield per unit area.
 
Materials and Methods
The agro-ecological requirements for rice cultivation were first identified using scientific resources and documents. Thematic maps were then prepared for a comprehensive set of variables, including annual precipitation, average/maximum/minimum annual temperatures, total sunshine hours, relative humidity, water resources, topographic features (elevation, slope percentage and aspect), and soil properties (texture, potassium, phosphorus, nitrogen, copper, manganese, iron, organic matter, electrical conductivity, and pH). Soil sampling was conducted from 128 points across the farmlands of 49 villages in the region, and the samples were analyzed at the central laboratory of Sari University of Agricultural Sciences and Natural Resources. Geostatistical and classical interpolation methods, including Ordinary Kriging, Radial Basis Functions, and Inverse Distance Weighting (IDW), were employed to extrapolate these variables across the study area, with the final method selected based on the lowest Root Mean Square Error (RMSE). The Analytic Hierarchy Process (AHP) was utilized to determine the weight of each environmental criterion, incorporating expert opinions. The weighted digital layers were then integrated within a Geographic Information System (GIS) environment. Land suitability was classified into four categories: highly suitable, suitable, moderately suitable, and unsuitable. Furthermore, the SSM-iCrop2 model, a native crop simulation model for Iran, was used to estimate the potential yield of paddy rice based on meteorological data, soil conditions, crop management practices, and plant parameters.
 
Results and Discussion
The results of the land suitability assessment revealed that only a small fraction of the agricultural land in the Hezar Jerib District is highly suitable for rice cultivation. Specifically, approximately 2.2% (637 ha) was classified as highly suitable, 16.7% (4,690 ha) as suitable, 40.5% (11,370 hectares) as moderately suitable, and 40.4% (11,355 ha) as unsuitable. The highly suitable areas are primarily confined to a narrow strip along the Nekarood River in the northern part of the region, characterized by flat terrain and proximity to water sources. The main factors limiting suitability were identified as steep slopes and inadequate water resources, with about 81% of the land deemed unsuitable or only marginally suitable due to these constraints. The SSM-iCrop2 model output indicated a potential paddy rice yield of about 3.92 tons per hectare for the region's agricultural land units. The current average yield achieved by local farmers was estimated at 3.2 tons per hectare, resulting in a relatively small yield gap of 0.72 tons per hectare. This minor gap is likely attributable to the recent adoption of modern mechanized equipment and could potentially be addressed by optimizing crop management practices, such as adjusting planting dates.
Conclusion
This study demonstrates that only a limited portion of the Hezar Jerib District possesses high suitability for rice cultivation, primarily due to topographic (slope) and water resource limitations. The findings underscore the necessity of aligning agricultural activities with the ecological capacity of the land to ensure sustainability. Expanding rice cultivation into non-suitable areas would require intensive inputs and management, potentially leading to environmental degradation and long-term loss of productive resources. Therefore, rice cultivation is recommended only in limited areas that have access to sufficient water and are properly leveled. The small yield gap suggests that significant increases in yield through improved management might be challenging under the current cultivation system. Future efforts could explore alternative cultivation methods, such as aerobic rice systems, to enhance water use efficiency, provided that challenges like weed control and the identification of suitable varieties are addressed.