24 - 25 October 2002, India International Centre, New Delhi, India
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Use of GPS for Farm level Mapping of Salt Affected Soils


Application of GPS in field survey
Field traverse and land contours formed the basis of selecting profile sites representing all categories of alkali soils occurring in the farm. A total of eight soil profiles were studied for their site characteristics and soil morphology. From each soil profile, horizon wise soil samples were collected for laboratory analysis and characterization. A number of intervening soil auger bore tests was performed to establish extensiveness of profile boundary. For better reproducibility of the sampling sites, longitude and latitude of each soil profile was recorded with the help of GPS, which are given in the table along with their land use and soil characteristics. The location of soil profiles was marked in the Farm map (Figure 1).

Usefulness of GPS in survey of SAS
Spatial distribution of SAS is patterned in the form of scattered patches of less than 1 hectare to more than 50 hectares amidst fertile soils. Besides, crop growth properties of SAS differ greatly from surrounding soils. These two unique characteristics makes it necessary to mark their sampling site in such a manner that it could be easily and accurately relocated in the post reclamation period. GPS marked location of sampling sites are easily and accurately identifiable. Thus various monitoring studies based on point data can be conducted with greater degree of precision. Use of GPS in surveys of SAS would definitely improve the quality of studies leading to; comparable study to monitor the improvement of soil properties in the post–reclamation period, precise detection of hot spots of salinity emergence & expansion and identification and establishment of benchmark sites of SAS.

Location of soil profiles marked with GPS, land use and characteristics of alkali soils at Shivari Farm, Lucknow Uttar Pradesh

Soil Profile Location as per GPS Value in Coordinates Land use and soil characteristics*
P1 26o 48’4. 0”N, 80o 46’10. 3”E Alkali soil, reclaimed with gypsum for 4 years, Under sugarcane crop. Soil pHs 8.7, ECe 0.6 
P2 26o 48’ 04”N, 80o 46’ 21”E Alkali soil, barren, pHs 10.1, ECe 1.4
P3 26o 47’58”N, 80o 46’24” E Alkali soil biologically reclaimed with Accacia for 4 years. PHs 8.9, Ece 0.9 
P4 26o47’51. 3”N, 80o46’32. 5”E Alkali sol, barren, pHs 9.5, ECe 1.6
P5 26o47’50. 5”N, 80o 46’29. 2”E Normal soil, low lying topography, pHs 8.0, Ece 0.7 
P6 26o 47’56. 5”N, 80o 46’21. 7”E Alkali soil, barren, pHs 10.7, ECe 10.7
P7 26o48’1. 6” N, 80o 46’16. 0” E Alkali soil, barren, pHs 10.7, ECe 15.2 
P8 26o48’9. 3” N, 80o 46’22. 0” E Alkali soil, reclaimed with gypsum for 4 years. Under rice-wheat crops, pHs 8.8, ECe 0.9


* For surface 15 cm soil, pHs = pH of the saturated soil paste, ECe = Electrical conductance of saturated soil solution in dS/m



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