6 Effect of Agricultural Management Practices
(e.g. Tillage, Organic Fertilization)
Agricultural management practices and soil enzymatic activity are closely linked.
On one hand, agricultural systems benefit from higher soil enzymatic activity due to
an improved land management responsiveness. On the other hand,
monoculture-based systems limit inter-species interactions, and thus bacteria
associations, since these are influenced by root exudate components that vary in
type and quantity according to different crop species [26]. Crop rotations, no-tillage,
organic amendments, the use of low weight machinery and cover crops are some
Conservation Agricultural (CA) practices known to favour enzyme activity [27].
A meta-analysis of 62 studies demonstrated that no till or reduced tillage promotes
large microbial communities and greater enzymatic activity [28], although further
study is necessary to understand the long-term (>10 years) impact on the microbial
communities under CA, e.g. [28] stated till and no-till microbial activity show
similar results after a 10 year period.
Tillage is performed to increase the aeration of the topsoil and provide weed
control. However, conventional tillage techniques can result in soil compaction due
to heavy machinery [29], which alters soil vertical structure, reducing soil organic
matter, plant nutrient availability over time and microbial biomass [30]. In fact, soil
compaction leads to a change in the soil atmosphere which may have negative effects
on soil biological activity that, in turn, will affect soil physical properties. Therefore,
plant growth may be repressed due to the negative effects on plant roots, because
aeration characteristics of soil and its effects on plant growth depends mostly on the
composition of air in the soil [31]. Curci et al. [32] studied the influence of tillage
(shallow ploughing, deep ploughing and scarification) on enzyme activity and
concluded the enzymes b-glucosidase, galactosidase, nitrate reductase and dehydrogenase were all affected negatively by tillage. These enzymes have different soil
functions and different pressure responses: glucosidase activities—responsible for
the hydrolysis of plant biomass—are inhibited in the presence of heavy metals (e.g.
copper [33]) and when there is soil acidification; dehydrogenase activities are highly
influenced by pesticides, remaining low when high doses of pesticides are traced
[34]. Conversely, no-till coupled with the incorporation of crop residues increases
microbial biomass as a response to an increase in SOM [32, 35, 36]. Urease is also
influenced by tillage activities as it is highly influenced by SOM content. Urease
catalyzes the hydrolysis of urea into carbon dioxide and ammonia and is commonly
used for soil quality evaluation versus its respective management [37, 38], although
enzyme activity performance is also dependent on environmental factors such as,
pH, oxido-reduction potential and, in particular, temperature and moisture [39].
Crop monoculture can lead to an imbalance in the main enzymes which has a
negative impact on soil function [23] subsequently causing a decline in soil quality
[40]. Microbial and biochemical analyses of soil under winter wheat in a field trial
with various cultivation systems (organic, conventional and monoculture) were
performed during three growing seasons [41]. The activities of the tested enzymes
142
C. M. d. S. Cordovil et al.
(e.g. Tillage, Organic Fertilization)
Agricultural management practices and soil enzymatic activity are closely linked.
On one hand, agricultural systems benefit from higher soil enzymatic activity due to
an improved land management responsiveness. On the other hand,
monoculture-based systems limit inter-species interactions, and thus bacteria
associations, since these are influenced by root exudate components that vary in
type and quantity according to different crop species [26]. Crop rotations, no-tillage,
organic amendments, the use of low weight machinery and cover crops are some
Conservation Agricultural (CA) practices known to favour enzyme activity [27].
A meta-analysis of 62 studies demonstrated that no till or reduced tillage promotes
large microbial communities and greater enzymatic activity [28], although further
study is necessary to understand the long-term (>10 years) impact on the microbial
communities under CA, e.g. [28] stated till and no-till microbial activity show
similar results after a 10 year period.
Tillage is performed to increase the aeration of the topsoil and provide weed
control. However, conventional tillage techniques can result in soil compaction due
to heavy machinery [29], which alters soil vertical structure, reducing soil organic
matter, plant nutrient availability over time and microbial biomass [30]. In fact, soil
compaction leads to a change in the soil atmosphere which may have negative effects
on soil biological activity that, in turn, will affect soil physical properties. Therefore,
plant growth may be repressed due to the negative effects on plant roots, because
aeration characteristics of soil and its effects on plant growth depends mostly on the
composition of air in the soil [31]. Curci et al. [32] studied the influence of tillage
(shallow ploughing, deep ploughing and scarification) on enzyme activity and
concluded the enzymes b-glucosidase, galactosidase, nitrate reductase and dehydrogenase were all affected negatively by tillage. These enzymes have different soil
functions and different pressure responses: glucosidase activities—responsible for
the hydrolysis of plant biomass—are inhibited in the presence of heavy metals (e.g.
copper [33]) and when there is soil acidification; dehydrogenase activities are highly
influenced by pesticides, remaining low when high doses of pesticides are traced
[34]. Conversely, no-till coupled with the incorporation of crop residues increases
microbial biomass as a response to an increase in SOM [32, 35, 36]. Urease is also
influenced by tillage activities as it is highly influenced by SOM content. Urease
catalyzes the hydrolysis of urea into carbon dioxide and ammonia and is commonly
used for soil quality evaluation versus its respective management [37, 38], although
enzyme activity performance is also dependent on environmental factors such as,
pH, oxido-reduction potential and, in particular, temperature and moisture [39].
Crop monoculture can lead to an imbalance in the main enzymes which has a
negative impact on soil function [23] subsequently causing a decline in soil quality
[40]. Microbial and biochemical analyses of soil under winter wheat in a field trial
with various cultivation systems (organic, conventional and monoculture) were
performed during three growing seasons [41]. The activities of the tested enzymes
142
C. M. d. S. Cordovil et al.