Buffering capacity against the alkalinity in the chilean soils of the V and Metropolitan Regions

Carlos Benavides Z.1, Manuel Casanova P.1 y Antonio Rustom J.1

Soil alkalinization induced by urea hidrolysis was simulated by the addition of a strong basis (NaOH) to 14 samples of surface soils from Central Zone of Chile. The slopes of the adjusted titration curves represent the buffering capacity of soils expressed through the so called buffering factors (BOH1 and BOH2). These values and some physical and chemical soil properties were analized by stepwise procedure, resulting in the following models:
BOH1 = 45.1068 + 1.2870(% sand) - 3.1220(% o.m.) R2 = 0.87.
BOH2 = 80.4541 - 0.4189(% clay) + 0.3035(% silt) - 6.8856(pH) - 1.5501 (E. C.) R2 = 0.93.
At the microsite level, only BOH1 is considered of equivalent importance to the alkalinization induced by urea granule of average size, and on an average soil. The variations in the values of BOH1 factor in the 14 soils tested, represent the effect of organic matter (o.m.) level and the diluting effect of the sand fraction.

Keywords: soil fertilizer reaction, urea, buffering capacity, microsite.
1 Departamento de Ingeniería y Suelos, Facultad de Ciencias Agrarias y Forestales. Universidad de Chile, Casilla 1004, Santiago, Chile.