Use of information technology for mapping of DTPA-extractable micronutrients in soils of Amritsar District, Punjab

Mapping of DTPA-extractable micro nutrients were carried out by randomly collecting georeferenced surface (0–0.15 m) soil samples representing different soils (as per soil map prepared on 1:50,000 scale) from 645 sites in Amritsar district (Northwest Punjab, India) using Global Positioning System (GPS) at flag leaf stage of wheat (Triticum aestivum L). The plant (flag leaves) samples were also collected simultaneously from every 4^th plant sampling site. These soil and plant samples were-analyzed for micro nutrients (Fe, Mn, Zn and Cu). The DTPA-Zn in soils varied from 0.18 to 3.91 mg kg⁻¹, DTPA-Cu from 0.16 to 3.96 mg kg⁻¹, DTPA-Fe from 1.83 to 30.6 mg kg⁻¹ and DTPA-Mn from 0.96 to 12.9 mg kg⁻¹. The contents of Zn in plants varied from 7.50 to 35.5 mg kg⁻¹, Cu from 3.50 to 11.5 mg kg⁻¹, Fe from 78.3 to 553.7 mg kg⁻¹ and Mn from 15.2 to 52.8 mg kg⁻¹. None of the samples were found to be deficient in Fe. The relationship between micronutrient contents in soil and plant was significant. There is a need to refine the critical level of deficiency for DTPA Fe with reference to growing environment, certain soil characteristics and pre-defined plant parts of specific crops. Soil micronutrient maps prepared in Arc Info GIS clearly delineated the specific locales where micronutrient problem constrained crop production. Multimicronutrient map suggested that deficiency of individual element is more prevalent as compared to that of two, three or four micronutrients. DTPA extractable micronutrients showed positive correlation with organic carbon and clay. The positive influence of organic carbon on micronutrient availability was maximum for DTPA-Cu. Comparison of DTPA extractable micronutrients for the year 1976 and 2003 indicated the deficiency of micronutrients increased over the years. These results indicated that Zn is likely to constraint crop production, followed by Mn in the soils of Amritsar district.