Geoscience Reference
In-Depth Information
of the saltating particles described above. Soil creep can move particles ranging
from 0.5 to 1 mm in diameter and accounts for 5-25 % of total soil movement by
wind.
There are several ways of controlling wind erosion. The cohesion of the constitu-
ents inside of aggregates is increased when the content of soil humus is increased
and when the humifi cation leads to the increase of glomalin content. If the rough-
ness of land surface is increased, the wind speed just above the surface is reduced.
A dense vegetation acts in a similar way to reduce the wind speed in the air close to
the land surface. Rows of trees around a fi eld serve as a windbreak to protect the
enclosed area against wind erosion.
14.3
How to Keep the Soil Healthy
The fi rst step is directed to the increase of aggregate stability and to balanced plant
nutrient resources. We have already mentioned that the majority of nutrients in soil
are stored in forms that are not immediately available to plants. At fi rst thought, this
seems ineffective, but it is a necessary feature of soils since only such nutrients are
stored and not leached out of soils. They are released as a function of time and usu-
ally in an adequate manner. Plant roots exude chemicals that help dissolve some of
the less soluble compounds as plant nutrients are being released. Plants are not able
to achieve this release completely by themselves.
Other organisms inhabiting soils help out and among them are the very effective
and benefi cial fungi called mycorrhizae (
M
). They have the ability to grow into the
roots of many plants, and at the same time, their fungal hyphae or branches grow
into the soil matrix.
M
fungi live symbiotically with the crops because they allow
access of needed nutrients from the soil to their plant partner. And then it is the
plant's turn to offer and share with the fungi its photosynthetically produced sugars
as an energy source. The
M
fungi make nutrients more accessible to crop plants by
several processes. They increase the extent of the plant root system within the soil
by exploring additional portions of soil favorable for root growth that enables a bet-
ter touch between the root and the soil matrix. Moreover, the
M
fungi have the abil-
ity to dissolve slightly soluble compounds containing plant nutrients. This ability is
especially important during instances when the exudation of crop roots is inade-
quate or less effective. Many plant nutrients even in soluble concentrations have low
mobility in soil. They are able to diffuse slowly and only few millimeters from their
release to the consumer - the plant root. It is therefore very effi cient when nutrients
are consumed very close to their release from more complex insoluble compounds
by
M
fungi. The effectiveness of
M
fungi can be easily increased by choosing spe-
cifi c crop rotations and reduced tillage systems. This principle is especially impor-
tant for the less mobile macronutrients of phosphorus and potassium and the
majority of most micronutrients of plants.
