TY  - BOOK
AU  - Aparna B 
AU  - Rajendran P (Guide)
TI  - Distribution, Characterization and Dynamics of Soil enzymes in Selected Soils of Kerala
U1  - 631.4 
PY  - 2000///
CY  - Vellayani
PB  - Department Of Soil Science And Agricultural Chemistry,College Of Agriculture
N2  - Biologically and biochemically mediated processes in soils are 
••• 
fundamental to the functioning of terrestial ecosystem. Understanding the 
,A 
underlying biological processes in tandem with identification of indicators of 
ecosystem stress is inevitable to provide strategies and approaches to promote 
long term sustainability of the fragile ecosystem. All members of the food 
chain are dependent on the soil as a source of nutrients, support and sustenance 
besides their reliance on soil as a sink for terrestial wastes. Now there is growing 
evidence to believe that soil biological parameters can hold potential as early 
and sensitive indices of soil degradation or restoration. In this context, soil 
enzymes play an active role in the microbial ecology and transformations 
brought about by catalysing enumerable reactions in soils. The activity of soil 
enzymes thus hold potential as soil quality indicators though they are sensitive 
to temporal changes due to environmental and management factors. Thus the 
long term effects of soil management techniques such as crop rotation, liming, 
fertilization and pesticide applications on the biological regimes need detailed 
investigations. Hence, with the overriding objective of projecting the effects 
of long term fertilization, application of soil amendments and agrochemicals 
on enzyme activities in relation to soil fertility, the present investigation was 
carried out. 
 
Analysis of soil samples collected from the experimental plots of five 
permanent manurial trials distributed in the coastal, midland and mid-upland 
regions of Kerala reveal drastic differences in the activities of five major soil 
enzymes, viz., urease, phosphatase, protease, dehydrogenase and cellulase. It 
is obvious from the study of permanent manurial plots of the Rice Research 
Station, Kayamkulam that the activity with respect to urease, protease and 
cellulase is low compared to the corresponding samples collected from the 
long term experimental plots of Pattambi, Balaramapuram and Chethackal. 
The activity of phosphatase and dehydrogenase reported in this case was 
moderate to high compared to Pattambi and Balaramapuram. In the case of 
protease and cellulase the highest activity was represented by samples collected 
from the Central Experimental Station of the Rubber Research Institute of 
India, Chethackal. In general, the highest activity with respect to all enzymes 
studied have been reported in the intercropping experiment at the Central 
Experimental Station, Chethackal, representing the hilly terrain and the lowest 
values were seen for the permanent manurial experiment at Balaramapuram. 
In the permanent manurial experiments, activities of the enzymes were 
found to be higher in plots receiving treatments involving combinations of 
organic manures and chemical fertilizers. It is evident from the study that the 
total quantity of organic amendments added to the soil per se could not sustain 
a higher microbial activity coupled with a higher enzyme activity, but required 
supplemental addition of mineral nutrients through chemical fertilizers also. 
Further, the role of supplemental addition of chemical fertilizers in the 
enhancement of enzyme activities was very clear from the stastically significant 
results obtained for the permanent manurial experiment at Pattambi. 
 
Significant differences in the enzyme activities have been observed in 
the case of the permanent manurial experiment at Balaramapuram consequent 
to the main and interaction effects of chemical fertilizers at higher levels of 
addition especially for urease, phosphatase and dehydrogenase. Hence it is 
clear from the study that the application of mineral fertilizers over a basal 
dose of organics could enhance the microbial activity of the soil to significantly 
higher levels yielding higher enzyme activities even in a highly weathered 
low activity clay soil like the red loam soil of Balaramapuram. 
Enzyme activities observed were the highest under the rubber based 
cropping system at Chethackal followed by the rice based experiments at 
Pattambi and Kayamkulam while the lowest activity was noticed at 
Balaramapuram. Of the physico-chemical characteristics studied through path 
co-efficient analysis and regression analysis, OC, CEC, ~03' available N, 
available P, available K and respiratory activity were found to influence the 
enzyme activities to the maximum extent. 
Pot culture experiments to study the effect of amendments and 
agrochemicals on enzyme activities revealed significant effects due to 
treatments. In all these cases, the maximum inhibitory effect on enzyme 
activities in general, were observed consequent to the application of antibiotics 
followed by fungicides, insecticides and herbicides. Immediately after the 
application of treatments there was a decline in the enzyme activity during the 
active tillering, the activity gradually resumed during the panicle initiation 
and then decreased asymptotically towards the harvest stage. Thus it is evident 
from the present study that considerable suppression of the enzyme activity is 
 
	
observed consequent to the application of agrochemicals though it is rendered 
relatively harmless over a period of time within the life span of the crop. 
However, the long term effect of this application need to be investigated in 
detail. 
Among the various amendments used in the present study, treatment 
involving the application of organic amendment as vermicompost in 
combination with lime and fertilizers was found to be significantly superior. 
All the five enzymes thus registered the highest value in this treatment 
irrespective of the stage of the crop.

UR  - http://krishikosh.egranth.ac.in/handle/1/5810015059
ER  -