Visveswaran, SSreekutty, M R.KAU2021-07-162021-07-162020174982https://krishikosh.egranth.ac.in/handle/1/5810170585PGThe present study entitled “Assessment of soil quality in the post- flood scenario of AEU 16 in Idukki district of Kerala and generation of GIS maps” was conducted during 2018-2020 with the objective of assessing the soil quality of post-flood soils of AEU 16, formulation of Soil Quality Index (SQI) and generation of GIS maps of soil characters and land quality. The study was initiated with the survey, collection followed by characterization of soil. Seventy-six representative geo referenced surface soil samples were collected from eight flood affected panchayaths viz., Rajakumari, Santhanpara, Senapathy, Udumbanchola, Pampadumpara, Karunapuram, Nedumkandam and Vandiperiyar. Cardamom, pepper, nutmeg, clove, ginger, paddy, cocoa, banana, cassava, vegetables etc. were the major crops grown. Farmers commonly use dolomite and organic nutrient sources like fresh and dried cow dung, goat manure, vermi compost etc. The soil samples were characterized for physical, chemical and biological attributes. The data was interpreted and Minimum Data Set (MDS) was developed using Principal Component Analysis (PCA). Eight principal components were extracted from which ten indicators that highly influenced the soil quality (eigen value >1) were identified, viz., bulk density, clay per cent, silt per cent, soil moisture content, pH, electrical conductivity, organic carbon, available N, K and B. SQI for each sampling site was generated by aggregating the scores following standard methods (Kundu et al., 2012). The relative soil quality index of the soils was also calculated and 77.6 per cent of soil samples had medium soil quality index. Correlation between the analysed parameters were worked out. Deposition of sediments with varying depth and texture was found in Rajakumari, Udumbanchola, Karunapuram and Vandiperiyar panchayaths, of which the sand deposition in Rajakumari panchayath was prominent. Most of the soils had a BD <1.2 Mg m-3 (80.3%), PD <2.2 Mg m-3 (88.2%), porosity between 30 and 50 % (68.4%), soil moisture content less than 10% (29.0%), WHC between 30 and 50% (79.0%), WSA between 50 and 70% (59.2%) and MWD < 1 mm (72.4%). Soil pH was found to be moderately acidic for 30.3 per cent of the soil samples. All the soil samples had low electrical conductivity in a range less than 1.0 dS m-1. Organic carbon was high for 85.5 per cent of samples. Available N was low for 77.6 per cent of samples. Available P and available K was high for 54.0 and 80.3 per cent of the samples respectively. Available Ca, Mg and available S were sufficient whereas available B was deficient for most of the samples. Acid phosphatase activity was between 10 and 25 μg PNP produced g soil-1 h-1 for 42.1 per cent of samples. The mean of relative soil quality index was found to be highest in Pampadumpara panchayath (60.9% - medium) and lowest in Senapathy panchayath (55.2% - low). Nutrient index for organic carbon was high for all the panchayaths except for Nedumkandam panchayath (medium). Nutrient index for available N was low in all panchayaths. Nutrient index for available P was high in Karunapuram, Rajakumari, Santhanpara and Vandiperiyar panchayaths, medium in Udumbanchola and Pampadumpara panchayaths and low in Nedumkandam panchayath. Nutrient index for available K was high in all panchayaths except in Senapathi panchayath (medium). Land quality was low for 65.8 per cent of samples. In comparison with the pre-flood data of GOK (2013), there is an increase in pH from strongly acidic to moderately acidic, warranting lower requirement of lime. The previous values of organic carbon, available P and available K were also high similar to the post-flood status, indicating that there is no shift in the status of these nutrients. Per cent of samples with adequate levels of available Ca and available B were similar in the pre-flood and post-flood study whereas per cent of samples with adequate available Mg and available S increased. Establishment of soil quality index is very important as far as soil health is concerned. It is advisable to analyse the physcio chemical characteristics of soil and derive soil quality index every year, in order to have an effective alternate site-specific management of crops especially in the events of natural calamities. Thus, the present study shows a need for the revision of soil management practices, as there is an improvement of major nutritional factor viz., organic carbon, available P and K requiring only lesser nutrient requirement for maintaining the crops with same level of productivity compared to pre-flooded condition in the AEU 16.EnglishThesis