Computation and prediction of the buffering capacity of organic amendments and fertilisers. [French]Original Title Expression et prediction du pouvoir tampon des amendements et des engrais organiques.

摘要

The buffering capacity (BC) of organic substrates used in agriculture as soil amendments or organic fertilizers are of high interest to prevent adverse effects of mineral fertilizers in the application band near seeds or juvenile seedlings. This is the effect of ammonia, nitrous or aluminum toxicity caused by the sudden and temporary pH flux due to the application of these fertilizers. However, to our knowledge there is no standard method for computing of the BC of organic substrates. In this study, a method by integral calculation, called BC_I, was developed and tested on 30 organic amendments and fertilizers (OAF) commonly used in agriculture in Quebec. These OAF were titrated with variable rates of diluted H₂SO₄ or NaOH. A linear and a punctual methods found in the literature were compared to BC_I. The integral method was found more appropriate to OAF titration curves, particularly for determining the global BC, integrating the curves obtained during both the acid and alkaline treatments, which was not possible with the other two methods found in the literature. On average, the potential alkalinity of the 30 OAF was higher than the total exchangeable acidity. The globol BC_I could be predicted with total Ca, exchangeable Ca, and total Al (r2=0.79). Likewise, the BC_I to acidity could be predicted using total Ca, exchangeable Ca, and pH_CaCl2 (r2=0.78).