MSc

The present study entitled ‘Quality assessment of Pokkali soils under
different land uses’ was undertaken to evaluate the soil and water quality of acid
saline Pokkali soils under different land uses and to develop geo-referenced database
and maps on soil characterization. For this purpose, surface soil samples and water
samples were collected from the selected panchayaths representing five land use
pattern in the Pokkali tracts. Initial survey was conducted on Pokkali area and five
panchayaths were selected from Ernakulam district namely, Kuzhippally,
Nayarambalam, Elamkunnappuzha, Edavanakkadu and Kottuvally with all the
selected land use patterns. The land use patterns under study were i) paddy alone ii)
paddy – shrimp iii) shrimp alone iv) fallow and v) mangroves.
The soil samples were analysed for their physical (texture, bulk density, soil
moisture constants, aggregate stability), chemical (pH, EC, CEC, base saturation,
available N, P, K, Ca, Mg, Fe, Cu, Mn, Zn, S, B) and biological (organic carbon,
dehydrogenase activity, microbial biomass carbon) attributes. Water samples were
also characterized for parameters like pH, EC, TSS and heavy metals. Measured
attributes were analyzed by one-way analysis of variance using statistical package
MSTATC to examine the effect of land use type on soil properties. Soil quality
evaluation was done by the method described by Andrews et al. (2002). Three main
steps of this technique includes, i) selection of minimum data set (MDS), ii) scoring
of the MDS indicators based on their performance of soil functions, and iii)
integration of the indicator scores into a comparative index of soil quality.
Analysis of variance revealed that land uses have significant effect on most
of the measured attributes except fine sand percent, base saturation percent, content
of Mg, Zn, organic carbon and dehydrogenase activity. The statistical analysis
resulted in selection of minimum data set which highly influenced the quality of the
soil. Indicators in the MDS included available water content, pH, fine sand percent,
aggregate stability, silt percent, available Mg, bulk density, available S, microbial
biomass carbon, available Mn, organic carbon, base saturation and EC. The highest
soil quality index (4.92) was observed in paddy- shrimp land use system in
Nayarambalam panchayath and least value (2.07) was observed in shrimp alone land
use pattern in Kottuvally panchayath. The observed soil quality index value was in
the order, paddy- shrimp> paddy alone> fallow> mangrove> shrimp alone. Based on
the relative soil quality index value, all land uses were categorized into three groups,
ie, poor, medium and good. Paddy- shrimp land use system in Nayarambalam
panchayath was the only one land use system coming under the ‘good’ category. For
all the panchayaths and RRS, Vyttila GIS based soil quality index maps were
prepared.