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The
dictionary defines ecology as the area of science dealing with the
inter-relationship of organisms and their environment. As compared to
other types of agricultural production, pasture ecology is particularly
interesting and complex because it involves animals, plants, soil, and
the many climatic and environmental factors that affect them.
As
indicated by the previous four articles in this series on pasture
ecology, many factors affect plant growth and survival. Since a given
factor varies in intensity over time, pastures are extremely dynamic.
Given the numerous influences that impact upon pasture plants, often
only a slight difference in degree of a particular influence, in
combination with other factors, may make the difference between survival
and death of an individual pasture plant.
In
a well-managed pasture, the practices imposed by the livestock producer
should be the factors that "tip the balance" in favor of
desirable species and reduce negative influences. Most pastures were
planted by a pasture manager and thereafter the stocking rate, the
grazing system used, the extent of application of lime and fertilizer,
applications of pesticides, as well as weather conditions have major
effects on pasture composition and productivity.
Collectively,
even minor influences can have important long-range effects. In many
cases, factors interact with each other, thus compounding the effects.
For example, if root growth of a seedling grass stand is poor due to
inadequate fertilization, later drought stress may be more damaging than
it otherwise would have been. Weakened plants not killed by the drought
may be more susceptible to disease. Overgrazing may further limit root
growth, with the ultimate result being death of plants.
In
some cases, one influencing factor can offset another. As an example,
tall fescue is not well adapted near the Gulf Coast due to high stress
related to droughty soils, heat and nematodes. Yet, in some low-lying
wet-natured fields in this area, it can persist well with proper
management. |
