In situ Soil Fractions (Sand, Silt and Clay Percentage) and pH Data at Sample Sites in Arid Region of India
The data presented here consists percentage of sand, silt, clay and pH at surface (~5cm) and subsurface (~5-15cm) at various sample locations in arid region of Great Indian Thar Desert falling in Rajasthan state of India. Mainly, the samples collected falls in four districts namely, Jaisalmer, Bikaner, Nagaur, and Jodhpur. A total of 24 soil samples, each with ~2 kg weight were collected at surface (~ 5 cm depth) and subsurface (between 5-15 cm depth) in the sample locations. The samples were randomly selected but ensured to be well distributed with a rationale that the sample site is having minimum of 5 ha of homogeneous signature with respect to soil texture variation as appeared from satellite imagery. Care was taken while selecting sampling locations such at that it won’t have any litter deposition or weed growth. Locations with excessive moisture content were also avoided. Also, the samples are chosen such that the landscape contains sparse vegetation and avoided sand dunes due to their potential to participate in aeolian process. Predominantly, species like Calligonum polygonoides, Aerva persica, Citrullus colocynthi, Prosopis Juliflora, Ziziphus mauritiana, Prosopis cineraria and Fagonia bruguieri were found in this landscape. Out of 24 samples, in one location we are unable to collect subsurface soil as there is bedrock after at a depth of 6 cm.
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All the 47 soil samples (24 samples from surface and 23 samples from subsurface) were brought to the laboratory and prepared for physical and chemical analysis. All before, samples were air dried before sieving them through a 2-mm sieve in the laboratory. The sieving process ensured the removal of boulders, small pebbles, root particles and litter from soil samples. Determination of percentage of sand, silt, and clay was done using international pipette method. Pipette method based on the different sedimentation velocities of particles with different diameters is considered to be one of the standard methods to determine the individual grain size fraction distribution. Organic carbon estimated for all the soil samples using the method endorsed by IS272-Part22 (1972) yielded nil or <.09%. Towards determination of soil pH (potential of the H+ ion) we have used pH meter.