Assesment of soil quality in the post flood scenario of AEU 14 in Idukki district of Kerala and generation of GIS maps
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Date
2020
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Department of Soil Science and Agricultural Chemistry, College of Agriculture, Vellayani
Abstract
A study entitled ‘Assessment of soil quality in the post-flood scenario of AEU 14 in Idukki district in Kerala and generation of GIS maps’ was carried out with objectives to evaluate the soil quality of the flood affected areas of AEU 14 in Idukki district, to work out the soil quality index and to map the various soil attributes and quality using GIS techniques. On the basis of the survey conducted, seventy eight georeferenced soil samples were collected from the severely flood affected panchayaths viz. Vazhathope, Kamakshy, Konnathady, Rajakkad, Mariyapuram, and Kanjikuzhy. Pepper, cardamom, coffee, cocoa, coconut, nutmeg and vegetables were the major crops in the area. Major- ity (91 %) of the farmers were small and marginal, adopting organic practices and lim- ing integrated with conventional fertilisers. The soil samples, collected from a depth of 0-20 cm, were characterized for phys- ical (bulk density, particle density, porosity, texture, water holding capacity, depth of sand/ silt/ clay deposition, soil moisture and aggregate analysis), chemical (pH, EC, OC, available N, P, K, Ca, Mg, S, B) and biological (acid phosphatase) attributes. The min- imum data set of indicators for computing the soil quality index was selected by princi- pal component analysis. Six principal components were extracted from which ten indi- cators that highly influenced the soil quality were identified, viz. available calcium, organic carbon, available magnesium, acid phosphatase activity, clay per cent, silt per cent, pH, electrical conductivity, water stable aggregates and available boron. Scores and weights were assigned to each indicator, and they were aggregated to compute the soil quality index. The relative soil quality indices of the soils were computed. Thematic maps of the analysed soil parameters were generated in ArcGIS software and interpo- lated by Inverse distance weighting method. Correlations were worked out between physical, chemical and biological parameters. Bulk density of 67 per cent sam- ples were in a range of 1.0 to 1.2 Mg m-3 and particle density of 72 per cent samples were in the range 2.0 to 2.4Mg m-3. Mean value of water holding capacity ranged be- tween 40-50 per cent. Soil porosity of 58 per cent samples was between 40 and 50 percent. 118 Soil textural classes of the samples were clay (42 %), clay loam (27 %), sandy clay loam (17 %), sandy clay (9 %) and loamy (5 %). Based on soil pH, the samples belonged to moderately acid (37 %), strongly acid (28 %), slightly acid (25 %) and very strongly acid (9 %) classes. Electrical conductivity was < 2 dSm-1. Organic carbon content was high in 70 per cent of the soils. Available nitrogen was medium in 67 per cent of the samples and available phosphorus was high in 65 per cent of the soil samples. Available K status was high in 54 per cent and medium in 32 per cent of the soils. Available Ca was adequate in 89 per cent whereas Mg and S were deficient in 49 per cent of the samples and B was deficient in 100 per cent of the samples. Significant correlation was observed between clay content and water holding capacity of the soil, and acid phosphatase activity and organic carbon content of the soil. Nutrient index of organic carbon was high in all panchayaths except Vazhathope which was medium. Nutrient index of available K was low in Vazhathope and high in other panchayaths. Land quality index of the soil samples were very low (35 %), low (60 %) and medium (5 %). Based on the relative soil quality index value, soils were categorized as medium (59 %), good (37 %) and poor (4 %). Relative soil quality index was the highest in Rajakkad and lowest in Vazhathope panchayath. Vazhathope pan- chayath was comparatively vulnerable to floods in terms of soil physical, chemical and biological attributes. Rajakkad panchayath exhibited better tolerance to floods and was resilient. Compared to 2013 data, a moderation in soil reaction, an increase in the organic carbon content, available P, K, Ca, and alleviation in deficiency status of Mg and S was observed in the post- flood soils, boron being an exception. An enhancement of soil quality parameters has been facilitated in the post-flood soils of AEU 14. Liming of acid soils, regular application of recommended doses of nitrogenous fertilisers, application of potassium fertilisers in splits, application of magnesium sul- phate in Mg and S deficient area, application of borax for crop plants are the suggested interventions for the soils of AEU 14 in Idukki district of Kerala.
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174979