Does
alfalfa have acidity?
Sebastian Gambaudo, Agricultural Engineer from the ENCaLAR Agreement
In dairy farms all over the provinces
of Santa Fe and Cordoba, alfalfa constitutes the major part of the fodder. It is used
directly or by mixing it with hay.
Thanks to the generic advances that we have experimented in the passed couple of years, we
count with productions of alfalfa that easily surpasses those from 20 years ago. Excellent
productions of dry materials also mean important extractions of calcium (Ca) and magnesium
(Mg), which are mainly taken from the superficial horizons of the ground. Therefore, for
example, 10.000Kg of dry material per hectare make up 105Kg of Ca and 25Kg of Mg.
Esto
se realiza a través de las determinaciones del porcentaje de saturación de bases, el
complejo de intercambio catiónico y el pH. estado de salud, el Ph da una idea del
estado de salud del suelo.
This extractions can modify what is
known as the ground’s acidity, generating in many occasions and environment that is
not appropriate for the grow and or development of the crop, in other words, difficulties
present themselves to achieve maximum performance. The chemical analysis of the soil is
the tool that let us know the characteristics of the soil. This is done by establishing
the saturation percentage of the base, the complex of cathionic interchange and PH.
Generally the first observation is that of the pH, which for the agronomist, this has the
same importance than fever has for a doctor. In the same manner that temperature gives an
indication of a man’s health condition, pH gives an idea of the ground’s health
condition.
Alfalfa is one of the most sensible species to soil acidity and when we correct it by
practicing whitewashing; we obtain satisfactory effects from a chemical, physical and
biological point of view.
In certain zones, acidity correction can considerably improve the concentration of
extractable phosphor (P). This also favors the efficiency of fertilizers because it does
not allow the formation of insoluble complexes.
Dangerous micronutrients in acid grounds
With
exception of the molybdenum (Mo), the solubility of all micronutrients increases with acid
pH and this can be unsafe due to the possibility of toxic effects in many of them when
their concentration increases in the soil’s solution.
The ground’s structure also benefits with calcium corrections, because due to the
stabilizing effect of calcium, it also increments the stability of the other ingredients.
It is well known that a better structure favors the ground’s ventilation, rain water
infiltration and roots penetration.
The
"binding" biological activity (symbiotic and non-symbiotic) of atmospheric
nitrogen (N2) finds its activity favored by pH above six. The beginning, establishment and
control of the associations between leguminous h. and rhizobium are complex and
sensitive to acidity.
The improvement of the chemical, physical and biological characteristics of the soil
that are achieved by calcium corrections improve the performance of alfalfa, as it was
observed in all of the central dairies.
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