Fuentes, R., Henríquez, J., Pinochet, D., Clunes, J.
Original Research Article, Soil Science
The use of sulfonylurea herbicides together with calcareous amendments is a common practice in acid soils derived from volcanic ash, especially in cereal crops. The objective of this study was to determine, through bioassays, the bioavailability of metsulfuron methyl and triasulfuron herbicides by liming in two soils derived from volcanic ash. The soils used were a Hapludand series Malihue and a Paleohumult series Fresia. The indicator species was pea (Pisum sativum L.), planted in pots with both soils and under four levels of liming (equivalent to 0, 1.9, 3.7 and 7.4 t ha-1 of Ca (OH)2) and 11 concentrations of herbicides. In each bioassay a control treatment with non-adsorptive substrate with non-limestone quartz was included. After 8 days of herbicide application, the radical length of the indicator species was measured and the values obtained were adjusted to a non-linear model, the dose that inhibited 50% of the radical development (ID50) in each treatment was determined. The bioavailability of each herbicide corresponded to the quotient between the ID50 obtained in the quartz substrate and the ID50 obtained in each treatment. The results showed that the adsorption of metsulfuron-methyl and triasulfuron decreased as the liming dose increased, increasing their relative bioavailability in both soils. The adsorption of triasulfuron with increasing lime applications was lower than that of metsulfuron-methyl in quantitative terms, but higher in relative terms. These results were corroborated when examining the adsorption coefficients (Kd).