MSc

Soil quality is directly related to agricultural sustainability. Assessment of soil quality is
essential for determining the sustainability of land management systems. It is generally accepted
that intensive agricultural production leads to a decline in soil quality. For this reason, it is
highly essential to monitor soil quality to avoid soil degradation and in doing so, preserve the
production capabilities of the land and protect environment. The response of soils to
management and input depends on soil quality. It is therefore important to identify the soil
characteristics responsible for changes in soil quality, which may eventually be considered as
soil quality indicators for assessing agricultural sustainability.
The present investigation has been undertaken to study the “Long term effect of field
management on soil quality in Ultisol”. It was conducted in the main campus of Kerala
Agricultural University, Vellanikkara during December, 2012 to June, 2013. The objective of the
study was to evaluate the soil quality under different long term field management conditions in
an Ultisol (Vellanikkara series) based on physical, chemical and biological indicators. Here, an
attempt has been made to evaluate the physical, chemical and biological properties of soil using
available soil quality indicators. Five different fields were selected namely, natural forest, rubber
plantation, cocoa garden, STCR experimental field and tapioca fields. Soil samples were
collected from three depths namely 0-15 cm, 15-30 cm and 30-60 cm. The different sampling
sites within each field were selected based on slope percentage. The samples were characterized
for soil texture, aggregate size distribution, soil temperature, water holding capacity, single value
constants, pH, EC CEC, AEC, SiO2/R2O3, organic carbon , lime requirement, available
macronutrients, secondary nutrients, micronutrients, counts of bacteria, fungi and actinomycetes
and enzyme activity. The sampling areas were also surveyed and documented for the presence of
earthworms and termites.
The physical characteristics like water holding capacity, soil aggregate stability and soil
temperature showed a decreasing trend with depth in the different fields. Forest ecosystem
showed the most conducive physical characteristics followed by cocoa and rubber. The contents
of available nutrients, secondary nutrients and micronutrients were found to be the highest in
surface samples. The forest ecosystem showed relatively high values for organic carbon, and
available nutrients like nitrogen, sulphur, boron, iron, manganese, zinc and copper. Microbial
activity was found to be the highest in surface soils in almost all fields. The highest counts of
bacteria and actinomycetes were reported in forest ecosystem and lowest in tapioca field. Fungal
activity was found to be the highest in cocoa field followed by forest ecosystem. Enzyme activity
was also found to be the highest in surface soils in the different fields.
Soil quality was evaluated using available soil quality indicators. Based
on scoring with the soil quality parameters, the highest scoring was observed for natural forest
followed by cocoa field. Correlations between various soil quality parameters of different fields
were also worked out.
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