Indira, MSumeena, K JKAU2020-12-292020-12-292020174937https://krishikosh.egranth.ac.in/handle/1/5810157571MScThe present study entitled “Assessment of soil quality in the post-flood scenario of AEU 4 in Pathanamthitta district of Kerala and generation of GIS maps” was undertaken to evaluate the soil quality of post flood soils in this area and to develop maps on soil characters and quality using GIS technique and to work out soil quality index. Seventy five geo referenced representative soil samples were collected from flood affected areas of Nedumpuram, Niranam, Kuttoor, Kadapra, Peringara panchayats and Thriuvalla Municipality. As per the survey details, rice, banana, nutmeg and vegetables are the major crops grown in the area. Majority of the farmers follow organic farming practices. In this region flood occurred mainly due to high rainfall and rise in water level in Pamba and Manimala rivers. Water stagnation continued in this area for 5-6 days and thick deposition of silt was observed in severely affected areas. Soil samples collected were analyzed for different physical (bulk density, particle density, porosity, texture, depth of silt/clay/sand deposition, maximum water holding capacity, soil moisture and aggregate analysis), chemical (pH, electrical conductivity, organic carbon, available macro, secondary and micronutrients) and biological (Acid phosphatase) parameters for evaluating soil quality. Selection of Minimum Data Set (MDS) was done by using Principal Component Analysis (PCA) method. The MDS which determine the SQI of these area are percentage of water stable aggregates, percentage of sand, silt and clay, pH, phosphorus, potassium, magnesium, manganese, iron and boron. These indicators are given weightage based on the influence of indicators on soil quality. These scores are integrated to determine SQI (Kundu et al., 2018). Relative soil quality index (RSQI) was also determined from this. Thematic maps of soil quality, land quality and nutrient index were prepared in ArcGIS software. Correlation between different physical, chemical and biological parameters were done statistically. Bulk density of 85.33% samples lies below 1.6 Mg m-3. Majority of the soil samples had particle density less than 2.67 Mg m-3. The present study showed that water holding capacity of 97.33% samples were greater than 30%. Mean weight diameter of 84% of samples had less than 1 mm. The predominant soil texture in this area is silt loam. Other samples have textural classes such as clay loam, silty clay loam, sandy clay loam and sandy loam. The soils of AEU 4 in Pathanamthitta are extremely acidic to near neutral with overall pH ranging from 4.02 to 6.98. Electrical conductivity of 80 per cent of samples had less than 1 dSm-1. The study area shown high content of organic carbon. Phosphorus was high in 56% of samples whereas 61.3% samples are low in Nitrogen and 49.33 5 of samples having medium potassium content. Majority of samples analysed were deficient in calcium, magnesium and sulphur. Near to 100% of the samples were having sufficiency in Fe, Zn, Mn and B whereas copper shown deficiency. 73.3% of samples had acid phosphatase activity less than 10 μg PNP produced g-1soil h-1. The results are compared with pre flood scenario data from Kerala State Planning Board (2013). Organic carbon and phosphorus remained high before and after flood. There is a slight decrease in pH from strongly acidic to ultra-acidic in this region. There exist a decrease in potassium from high to medium level. Zn, Mn, Fe and B remained sufficient whereas calcium and magnesium remained deficient before and after flood. Sulphur and Copper showed a drastic change from sufficiency to deficiency. According to the SQI analysis, highest soil quality was found in Niranam panchayat and lowest in Peringara. As per nutrient index analysis, all the Panchayats have high organic carbon and low nitrogen status. Peringara and Thiruvalla Municipality had low Phosphorus status and all others with high P status. Potassium was medium in Thiruvalla municipality and Niranam panchayat whereas all other panchayats have low K fertility status. Land Quality index (LQI) was high in Nedumpuram Panchayt. From the present investigation, AEU 4 in Pathanamthitta showed that there is an increase in overall soil acidity and depletion in the status of nitrogen, potassium, sulphur and copper which indicates that the nutrients might be lost due to flooding. So site specific management practices are necessary. Alteration in nutrients application according to the current status of soil will help to achieve productivity.EnglishThesis