MSc

ABSTRACT A study entitled “Soil quality assessment and generation of GIS maps in flood affected Mananthavady block of Wayanad district” was conducted during 2018-20 with the objectives to assess the soil quality of post-flood soils of Mananthavady block in Wayanad district, to work out the soil quality index (SQI) and to develop maps on soil characters using GIS techniques. A preliminary survey was conducted to identify the flood affected areas and to understand the cropping history and nutrient management practices of the locality. It was found that, the entire area consisting of five panchayaths namely Vellamunda, Thirunelly, Thondernadu, Edavaka and Thavinhal and Mananthavady municipality were affected by flood. Banana, paddy, coffee, pepper, vegetables, arecanut, coconut, rubber and tea are the major crops grown in the area. Majority (96%) of the farmers belonged to the small and marginal category with farm size less than 2ha. Geo-referenced surface soil samples were collected from a depth of 0-20cm from hundred flood affected locations of Mananthavady block for analysing physical, chemical and biological properties. Principal Component Analysis (PCA) was used for the selection of Minimum Data Set (MDS) for the assessment of Soil quality. The selected parameters were ECEC, pH, organic carbon, percent silt, Available Fe, K, B, S, P, and Zn. Soil Quality Index (SQI) was computed for each sampling location by assigning scores and weight to each MDS parameter. Thematic maps of various soil attributes, soil quality, land quality and nutrient indices were generated in ArcGIS 10.3 software. The investigation revealed that, the majority of the area had a bulk density between 1.4 and 1.6 Mg m-3(61%), particle density between 2.2 to 2.4 Mg m-3 (50%), porosity between 30 and 50 percentage (85%) and 70 % of the samples recorded maximum water holding capacity between 30 and 50 percentage . The predominant soil textural class in the study area was sandy clay loam (60%) followed by clay loam (17%) and sandy loam (14%). Chemical analysis showed that, the study area was dominated by very strongly acid soils (47%) followed by strongly acidic (25%) soils and 51% of soils had
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exchangeable acidity between 2 and 4 cmol (p+) Kg-1. Electrical conductivity was less than 1 dSm-1 in all over the study area. Organic carbon content was medium in 61 % of the soils and available nitrogen was low in 94 % of the samples. The available P (64%) and available K (41%) were observed to be medium in the study area. Available calcium and magnesium were found to be adequate in 87% and 93% per cent of soil samples respectively. Majority of the soils were deficient in available S (85%) and were sufficient in available Cu (73%). The entire study area was sufficient in available Fe, Mn, Zn and was deficient in available B. Most of the study area had a low status of exchangeable Na (96%), exchangeable Al recorded values between 2 and 4 cmol (p+) Kg-1(49%) and ECEC between 5 and 16 cmol (p+) Kg-1 (94%). The soil quality was worked out by SQI and it was found to be good in 24% of the study locations, whereas 73% of the samples recorded soil quality at medium level. Highest mean value of soil quality was observed from Thondernadu followed by Vellamunda and lowest value was reported from Thirunelly. Nutrient index of organic carbon was high in Thondernadu and medium in other panchayaths. Whereas Nutrient index of nitrogen was low in entire study area. Nutrient index for phosphorous was medium in Thondernadu, and Vellamunda and was high in all other panchayaths. Nutrient index for potassium was low in Thirunelly and Edavaka and was medium in rest of the areas. Land Quality Index of 69% of study area were found to be very low. Comparison of post flood with pre flood data of KSPB (2013) showed that, there was a decrease in extremely acid and moderately acid soil test values. The post flood data also revealed that there was an increase in available P, Ca, Mg, Zn, and Cu whereas there was a decrease in organic carbon content and availability of potassium, sulphur, and boron. Thus the variations in the status of pH, organic carbon and nutrients compared to pre flood study necessitate a revision in soil management practices.