Physico-chemical processes IV. Stratifications in the soil profile

Stratifications in the soil profile are complicated processes in which different soil elements move between the heights that make up the profile. In this entry we are going to study the profile of a specific green, where we have taken two samples at different depths, one between 0-10 cms and the other between 10-20 cms.

Studying the chemical evolution of a surface over time is one of the best ways to obtain information and make good agronomic decisions.

The different physico-chemical processes that we have studied generally refer to the shallower parts of the soil, as these are the areas from which samples are usually taken. But it is interesting to see what happens in the deeper parts. In this way we can understand what processes occur in the different soil horizons.

Piper diagrams are simple diagrams that facilitate the comparison between Ions and Cations of elements under study. Different soils, different soil horizons or the interaction between soil and irrigation water can be compared.

In the piper diagram we can observe two dots representing each horizon of the profile, the green one being the upper horizon with 368 ppm of salts obtained in the saturated extract and a red dot with 564 ppm of salts for the lower horizon of the soil profile. This indicates that salts are leaching from the surface to the deeper layers.

A change in the 20% of carbonates and sulphates is observed, with one increasing and the other decreasing with the depth of the profile. In addition, there was also a slight increase in iron at depth. The pH study resulted in an increase of more than half a point in the shallower sample (pH 7.7) with the deeper sample (pH 8.25), probably due to the lower pH (pH 8.25). soil respiration and the migration of soluble carbonates.

The evolution of the profile is shown very graphically thanks to the diagrams.

All these observations make us estimate what happens along the soil profile for each particular case. In this example there is a trend of a very important proportional increase of Carbonates and a similar decrease of Sulphates as one descends to the lower strata of the soil profile.

The increase in iron in depth in this case, is likely to take place due to changes in pH value. Research shows that pH controls its movement in the soil profile, especially in strata that move from low to high pHs. There is documentation explaining situations with cemented horizons with iron oxides and clay in the boundary horizons between low pH sands and high pH gravels.

Tiloom advises to study the physico-chemical processes that take place in the profile of sports surfaces, both at the same point in time and at different points in the profile at the same time.

Surface-applied iron is highly soluble in low pH sands, but this solubility decreases with increasing pH in high pH gravels, precipitating in the stratum separating sand and gravel. The pH controls the movement of iron in the short term, while the redox potential controls the movement of Iron in the long term. This is why sealing horizons occur in neutral or alkaline substrate mixtures, although it should be noted that the visual presence of these horizons does not necessarily mean that drainage or infiltration will be compromised. Source: Glen Obear & Bill Kreuser, University of Nebraska, Lincoln.

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