Soil structure

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Proper soil structure for high-performance agriculture

Soil structure and plant cover functioning
Among the different environmental characteristics, soil structure is often neglected, although it has a strong impact on water and nutrient access and uptake by the crop. If the state of the soil structure is unknown, a crop malfunction can be totally misinterpreted and thus improperly corrected.

Soil structure and irrigation
Soil structure and soil texture also have an impact on water infiltration rate and thus on water management efficiency: water losses from evaporation or runoff are either reduced or increased when soil structure is modified.

The problem in arid areas is that soil structure is more fragile than anywhere else because of intensive irrigation. In these conditions, high-performance agriculture then greatly relies on a proper diagnosis and management of soil structure states. It is the only way to improve both water availability and infiltration, since soil texture cannot be modified.

For many years, ICS's attention has been focused on selecting the most appropriate equipment and agronomic solutions to preserve or even improve soil structure. Find in this page more information on soil structure impact on water infiltration and plant functioning.

Soil preparation
Soil preparation

Impact of soil structure on plant cover functioning

Affected characteristics are growth, distribution and functioning. Compaction increases pressure on cell walls which reduces root elongation speed and increases their diameter. The plant can respond by reducing the osmotic potential in the root. In this way, elongation is maintained if compaction is not too strong (Demissy and Farque, 1997). Apart from compaction, some researchers think that elongation reduction could also be the result of a chemical messenger synthesized in the roots (Tardieu, 1994). Root growth decrease makes the plant more sensitive to drought : the impact of a water deficit, even a superficial one is both quicker and stronger.

Compaction also modifies the root respiratory system. Respiration is increased which means that more oxygen is required.

Compaction reduces gas circulation in the soil at a moment where the roots need more oxygen to satisfy respiration increase (see above). This situation can lead to hypoxy problems.

Access to water can be more difficult because the soil close to the roots tend to dry more quickly. The resistance to water transfer towards the roots gets stronger. But water uptake is essentially limited by the heterogeneous distribution of the roots in the soil. This, of course, has direct consequences on the absorption of nutrients such as nitrate-nitrogen which are soluble in water.

Leaf expansion rate (LER) is reduced when the plant is grown on a compact soil (data on maize, Ben Haj Salah, 1996). This reduction doesn't seem to be the result of more ABA synthesis (stress hormone synthesized in the roots and brought up to the leaves). Another agent from the roots could be responsible but research results vary on this point.

Impact of soil structure on water infiltration

Water infiltration rate is partly influenced by soil structure. The more compact the soil, the slower the infiltration. Thus, a destruction of soil structure leads to water losses by evaporation and possibly runoff.

Diagnostic methods

Since soil structure has a strong impact on cover functioning and water infiltration, it must be properly characterized. Different methods can be used cultural profile, porosity measurements, Proctor curves ...

Cultural profile
This observation method is used for diagnostic purposes. The profile is defined as a series of horizons created by the use of agricultural machinery and root growth. The volume of studied soil is separated in units, each unit having a unique history in terms of management practices (agricultural equipment used).

Two levels of observation are used: the internal state of structural elements and the way in which these elements are put together (Manichon, 1982).

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