The land is the base for all human activities in the world. Land suitability is the fitness of a given type of land for a defined use. The land may be considered in its present condition or after improvements. Land suitability analysis can be made for various purposes. It started mainly for agriculture and many methods have been followed for agricultural production and sustainable agriculture. FAO (1975, 1976, 1996) has suggested methods based on physical and soil parameters of various countries in the world. Young et al. (1977), shah et al. (1988), and Jyothirmayi et al. (2019) have also suggested land suitability and land evaluation methods in their studies. There are several methods used for land suitability analysis. In this paper, an attempt is made to derive land suitability classes by considering relief, landforms, slope, aspect, topographic wetness index (TWI), soils, soil texture, and erosion-prone areas. The relief map is prepared by digitizing contours from the Survey of India’s topographic maps in 1:50,000 scale. SRTM data also used to derive contours, slope, aspect, and topographic wetness index.

To achieve the objectives, an attempt is made to derive land suitability classes by considering relief, landforms, slope, aspect, topographic wetness index (TWI), soils, soil texture, and erosion-prone areas. The relief map is prepared by digitizing contours from the Survey of India’s topographic maps in 1:50,000 scale. SRTM data also used to derive contours, slope, aspect, and topographic wetness index. Landform map is derived from relief and slope maps. Soils and soil texture map is prepared based on Soil Survey Department publications, satellite imagery, and field work. Erosion prone area map is prepared by using relief, slope, and drainage density. Water bodies and settlement areas were classified using satellite imagery.

Relief is an important aspect of the consideration of agriculture and productivity. Crops like paddy, coconut, banana, and vegetables will grow better in the low land and productivity will be higher. Rubber would grow up to 600 meters and give better yield. It also needs a drainage facility. It prefers land with a slope to plain. Coffee can grow from 600 to 1000 meters and give a better yield. Tea needs cool and higher elevation than coffee. 

Landforms also play important role in agriculture. It is a combination of geology, relief, and slope. Some crops prefer plain regions and others prefer land with different degrees of slopes. The flat duricrust (hard laterite) low plateau region above 40 to 60 meters is a unique landform feature of this district. It is an indurated hard laterite surface. Because of the hard and flat nature of this landform, it is barren and promotes surface runoff.

Slope plays a very important in agriculture. Certain crops like rubber, pepper, and coffee need land with slope and drainage. Very steep slope lands are not suitable for agriculture as it triggers soil erosion and landslides.

Aspect i.e., slope direction is also important to get water. Since this district gets rainfall mostly from the southwest monsoon, slopes facing south, southwest, and west are more favorable get water and stream formation and water flow.

Topographic Wetness Index (TWI) is a terrain index. It is a combination of degree of slope and slope area. Higher the TWI values higher the availability of water. Lower the index value lowers the availability of water. Availability of water can be assessed with the help of this index which is very important for agriculture, crops, and yield.

Soil types: Different types of soils also play an important role in agriculture. Alluvial soil is a transported soil mixed with humus and other soil nutrients. It is found generally in the river valleys and plain region. Forest loam is covered in the higher elevations of the eastern part of the district. Hard and soft laterite covers the midland region of the district. Crop combination and cropping patterns vary according to the soil types of the district.

Table 0

Soil Texture	Sandy	2
	Sandy loam	4
	Clay loam	6
	Laterite	3
	Duricrust	1
	Forest loam	5
Soils	1	4
	2	4
	5	4
	7	1
	8	3
	9	2
	10	3
	13	1
	20	1
	21	2
	22	2
	23	3
	24	2
Erosion Prone areas	3-6	1
	6-9	2
	9-12	3
	12-16	4
	16-24	5

Source: Compiled by the author

Soil texture is another important factor for the growth of the crops and root system of the plants. It plays an important role in the percolation of surface water to the groundwater and maintains soil moisture for the growth of crops and trees. 

Erosion prone area is prepared by using relief, slope, and drainage density.

All these eight parameter maps were digitized using ArcGIS software. They were converted into raster file and reclassified them according to the suitability for agriculture. Overlays were made with reclassified values of the layers and summed up the weightage using the spatial analyst tool in ArcGIS. Sum weightage map was reclassified into five classes from the lower value to higher values. The first three ranks of higher values are considered suitable for cultivation. The last two values were considered as not suitable for cultivation. They were labeled as most suitable (S1), moderately suitable (S2), marginally suitable (S3), not suitable (NS1), and not suitable (NS2). 

When all the 8 reclassed weightages maps were overlaid using the weighted Sum sub-tool from the Spatial analyst tool in ArcGIS, got a map with weights ranging from 15 to 50. This was reclassed into 5 classes as mentioned earlier. In NS2, water bodies and urban and settlement areas are included as they cannot be used for agriculture. This map was converted into vector format and area calculated for each class. The area under each class of suitability and the percentage to the total area of the district is given in the following table.

Figure 2

The application of the GIS technique in land suitability classification has the greatest potential and capabilities in analyzing and preparing maps for the Kannur district. This study derived land suitability classes by considering relief, landforms, slope, aspect, topographic wetness index (TWI), soils, soil texture, and erosion-prone areas and prepared a land suitability map, which is much closer to the field reality. The present investigation can be useful for identifying the main limiting factors for agricultural production and enables decision-makers to develop crop managements able to increase the land productivity of Kannur district.