Enzymes

Soil enzymes

 Soil enzymes are a group of enzymes whose usual inhabitants are the soil and are continuously playing an important role in maintaining soil ecology, physical and chemical properties, fertility, and soil health. These enzymes play key biochemical functions in the overall process of organic matter decomposition in the soil system. They are important in catalyzing several vital reactions necessary for the life processes of micro-organisms in soils and the stabilization of soil structure, the decomposition of organic wastes, organic matter formation, and nutrient cycling, hence playing an important role in agriculture.The enzyme levels in soil systems vary in amounts primarily due to the fact that each soil type has different amounts of organic matter content, composition, and activity of its living organisms.

 Kind of Soil Enzymes

 1. Constitutive

 Always present in nearly constant amounts in a cell (not affected by addition of Any particular substrate – genes always expressed). (Pyrophosphatase)

 2. Inducible

 Present only in trace amounts or not at all, but quickly increases in concentration when its substrate is present. (Amidase) Both types of enzymes are present in the soil.

 Origin and State of Soil Enzymes

 Although the general origins of soil enzymes are (a) microorganisms-living and dead, (b) plant roots and plant residues and, (c) soil animals; the state of soil enzymes in the soil is different as below. In soil the enzymes are stabilized in clay,organic matter and also with organic matter clay complexes, which offers more advantage for the soil enzymes 

Most activities are associated with clays. Due to stabilization in clays, the enzymes get increased resistance to proteolysis and microbial attack as well as the inactivation temperature gets increased. Humus material provides stability to soil nitrogen compounds and also stabilization in soil organic matter provide stability under pH and temperature changes.

 Importance of Soil Enzymes 

•  Release of nutrients into the soil by means of organic matter degradation 

•  Identification of soils 

•  Identification of microbial activity

•   Importance of soil enzymes as sensitive indicators of ecological change 

Application of Soil Enzymes 

•  Correlation with soil fertility  

• Correlation with microbial activity 

•  Correlation with biochemical cycling of various elements in soil (C, N, S) 

•  Degree of pollution (heavy metals, SO4)  

• To assess the successional stages of an ecosystem 

•  Forensic purposes 

•  Rapid degradation of pesticides 

•  Disease studies

•  Soil Enzymes as Indicators of Soil Health

 Soil health can be defined as the continued capacity of soil to function as a vital living system, within the ecosystem and land-use boundaries, to sustain biological productivity, promote the quality of air and water environments, and maintain plant, animal, and human health

 Why soil enzymes are considered as indicators of soil health?

 Enzymes are the direct mediators for biological catabolism of soil organic and mineral components. Thus, these catalysts provide a meaningful assessment of reaction rates for important soil processes.

Soil enzyme activities :-

(1) are often closely related to soil organic matter, soil physical properties and microbial activity or biomass .

(2) changes much sooner than other parameters, thus providing early indications of changes in soil health.

(3) involve simple procedures. In addition, soil enzyme activities can be used as measures of microbial activity, soil productivity, and inhibiting effects of pollutants.