Rajasthan Soils

Despite the recent great strides in technology and mechanization, agriculture has remained the world's most important primary industry, in which the soil plays pivotal role. About 66 per cent of the global population, comprising of farmers derives its living directly from the soil. There are no natural resources more important than soil resource.

Whatever its production capacities, whether high in some places of irrigated pockets or low in major areas of dryland and desert, due to inherent limitations, the soil resource of Rajasthan, as a medium of growing crops, has furnished directly or indirectly, a significant share in the income of the state. Rajasthan, being geographically the second largest state in India, has proportionately a greater soil resource. Therefore, the soil resource in the state needs to be used extensively and efficiently so that the state finds an appropriate place in the national food, fibre and fodder production and the state economy is sustained without any depletion through erosion, degradation or overuse. The information and knowledge of soils of the state which could be gained through the study of their physical and chemical properties and their geographical distribution pattern, is an essential prerequisite for their proper utilization, management and conservation. It also helps in proper selection of crops and better land use.

When seen in detail at the village level, the soils of Rajasthan are complex, and highly variable, reflecting a variety of differing parent materials, physiographic land features, range of distribution of rainfall and its effects, etc. However, broadly, the soils can be put in five major groups, based on the basic fabric of soils i.e. soil texture which governs its many other properties. They are, (1) sandy soils or light soils, (2) sandy loam or light medium soils, (3) loam or medium soils, (4) clay loam to clay or heavy soils and (5) skeletal soils or shallow rocky and hilly soils.

The soils are generally evaluated for their production capacity through study of their ability to supply plant growth requirements in terms of water, nutrient and rooting media. The capacity to retain, as also to conduct soil moisture in profile, depends upon the soil texture, soil porosity and soil structure. For example, heavy soils due to their fine texture and porosity, provide effective capillary tubes for moisture movement. In loose sandy soils, due to big particles and ores, with fewer fine capillary pores, there is lesser soil moisture movement. Further, heavy soils are more difficult to work with implements than in light soils. During dry hot periods, however, heavy soils that get compacted, resist wind erosion but under heavy rainfall, due to their low infiltration rates they generate high surface run off and thus cause extensive soil erosion through water. On the other hand, the sandy or light soils that are loose and single grained are more prone to wind erosion and are often subject to sand drift, but due to their coarse and open texture, coarse pores and resultant high infiltration capacity, they are not susceptible to water erosion, even during heavy cloud bursts. Medium textured soils have moderate condition between the above extremes. As such, these different soils create different types of habitats for plant growth, and therefore, the crop choice and cropping patterns on such kind of soils greatly vary.

Soils are thus, variable in their soil-water-plant relationship, conservation needs and production potentials. To assess the potential of agricultural development and to plan proper conservative land use, soil survey is the basic requisite. The knowledge of soils gathered through such surveys is not only useful in finding out agriculturally potential areas but also those areas which have remained unnoticed under one or the other soil degradation process for a long period and are now considered as problematic areas. Further, the aeronomical and soil moisture conservation technologies, developed for crop production, are often more suitable, particularly for one or the other kinds of soils. Therefore, the distribution of such differing soils depicted through soil survey maps, is useful for easy and proper transfer of such technologies to suitable areas.

Soil resource is also a malleable environment moulded by the agriculturist in many ways e.g. production capacity per se can be improved through improvements of its fertility by use of organic manures and fertilizers. Its sustainability can also be maintained by its conservation against damages through erosion, preventing salinization, alkalinization, compaction depletion in nutrient level, etc. These are all known soil degradational processes which lessen the current or potential capability of soils to produce crops or biomass. Many technologies are available to check this and conserve soils for sustained productivity.