[Quality of commercial inoculants for soybean crop in Argentina: concentration of viable rhizobia and presence of contaminants].

In view of the inoculant production technology available, quality control is a necessary tool to improve soybean inoculants commercialized in Argentina. In 1988, the Facultad de Ciencias Agropecuarias de la Universidad Nacional de Entre Ríos (Argentina) created a quality control service for soybean crop inoculants to offer to farmers. The aim of this study was to evaluate the quality of soybean crop inoculants for seven cropping seasons and to contrast these results with those from previous investigations conducted in our country. This work was developed using 128 inoculant samples from 30 different trade names. The analyzed variables were: inoculant label information, number of viable rhizobia and presence of contaminants. Twenty per cent of the labels showed defects that did not comply with the Argentine legislation. The detected problems in inoculant labels were related to lot numbers or the expiry date, which lacked, was easy to remove or not visible. Eighty seven per cent of the analyzed inoculants were formulated in liquid carriers. Seventy six per cent of the samples had a number of rhizobia above 10(8) CFU/g or ml, the minimum quantity required by the legislation. Thirty per cent of the analyzed inoculants had contaminants and their presence was related to low rhizobia counts, as shown in a correspondence analysis. The relationship between liquid inoculants and the absence of contaminants was expressed. It can be concluded from the comparison of results found in this investigation with those in previous works published on Argentinean inoculants, that inoculant quality has been improved, although the situation is far from ideal. Adequate manufacturing and commercialization controls are necessary to ensure product quality.